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-----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCXjFo8wAKCRCRxhvAZXjc omaGAQDVwCHQekqxp2eC8EJH4Pkt+Bn1BLrA25stlTo93YBPHgEAsPVUCRNcrZAl VncYmxCfpt3Yu0S/MTVXu5xrRiIXPQk= =uqTN -----END PGP SIGNATURE----- Merge tag 'threads-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux Pull thread management updates from Christian Brauner: "Sargun Dhillon over the last cycle has worked on the pidfd_getfd() syscall. This syscall allows for the retrieval of file descriptors of a process based on its pidfd. A task needs to have ptrace_may_access() permissions with PTRACE_MODE_ATTACH_REALCREDS (suggested by Oleg and Andy) on the target. One of the main use-cases is in combination with seccomp's user notification feature. As a reminder, seccomp's user notification feature was made available in v5.0. It allows a task to retrieve a file descriptor for its seccomp filter. The file descriptor is usually handed of to a more privileged supervising process. The supervisor can then listen for syscall events caught by the seccomp filter of the supervisee and perform actions in lieu of the supervisee, usually emulating syscalls. pidfd_getfd() is needed to expand its uses. There are currently two major users that wait on pidfd_getfd() and one future user: - Netflix, Sargun said, is working on a service mesh where users should be able to connect to a dns-based VIP. When a user connects to e.g. 1.2.3.4:80 that runs e.g. service "foo" they will be redirected to an envoy process. This service mesh uses seccomp user notifications and pidfd to intercept all connect calls and instead of connecting them to 1.2.3.4:80 connects them to e.g. 127.0.0.1:8080. - LXD uses the seccomp notifier heavily to intercept and emulate mknod() and mount() syscalls for unprivileged containers/processes. With pidfd_getfd() more uses-cases e.g. bridging socket connections will be possible. - The patchset has also seen some interest from the browser corner. Right now, Firefox is using a SECCOMP_RET_TRAP sandbox managed by a broker process. In the future glibc will start blocking all signals during dlopen() rendering this type of sandbox impossible. Hence, in the future Firefox will switch to a seccomp-user-nofication based sandbox which also makes use of file descriptor retrieval. The thread for this can be found at https://sourceware.org/ml/libc-alpha/2019-12/msg00079.html With pidfd_getfd() it is e.g. possible to bridge socket connections for the supervisee (binding to a privileged port) and taking actions on file descriptors on behalf of the supervisee in general. Sargun's first version was using an ioctl on pidfds but various people pushed for it to be a proper syscall which he duely implemented as well over various review cycles. Selftests are of course included. I've also added instructions how to deal with merge conflicts below. There's also a small fix coming from the kernel mentee project to correctly annotate struct sighand_struct with __rcu to fix various sparse warnings. We've received a few more such fixes and even though they are mostly trivial I've decided to postpone them until after -rc1 since they came in rather late and I don't want to risk introducing build warnings. Finally, there's a new prctl() command PR_{G,S}ET_IO_FLUSHER which is needed to avoid allocation recursions triggerable by storage drivers that have userspace parts that run in the IO path (e.g. dm-multipath, iscsi, etc). These allocation recursions deadlock the device. The new prctl() allows such privileged userspace components to avoid allocation recursions by setting the PF_MEMALLOC_NOIO and PF_LESS_THROTTLE flags. The patch carries the necessary acks from the relevant maintainers and is routed here as part of prctl() thread-management." * tag 'threads-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim sched.h: Annotate sighand_struct with __rcu test: Add test for pidfd getfd arch: wire up pidfd_getfd syscall pid: Implement pidfd_getfd syscall vfs, fdtable: Add fget_task helper
1037 lines
25 KiB
C
1037 lines
25 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
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* linux/fs/file.c
|
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*
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* Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
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*
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* Manage the dynamic fd arrays in the process files_struct.
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*/
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#include <linux/syscalls.h>
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#include <linux/export.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/sched/signal.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/bitops.h>
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#include <linux/spinlock.h>
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#include <linux/rcupdate.h>
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unsigned int sysctl_nr_open __read_mostly = 1024*1024;
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unsigned int sysctl_nr_open_min = BITS_PER_LONG;
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/* our min() is unusable in constant expressions ;-/ */
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#define __const_min(x, y) ((x) < (y) ? (x) : (y))
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unsigned int sysctl_nr_open_max =
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__const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
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static void __free_fdtable(struct fdtable *fdt)
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{
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kvfree(fdt->fd);
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kvfree(fdt->open_fds);
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kfree(fdt);
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}
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static void free_fdtable_rcu(struct rcu_head *rcu)
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{
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__free_fdtable(container_of(rcu, struct fdtable, rcu));
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}
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#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
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#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
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/*
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* Copy 'count' fd bits from the old table to the new table and clear the extra
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* space if any. This does not copy the file pointers. Called with the files
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* spinlock held for write.
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*/
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static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
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unsigned int count)
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{
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unsigned int cpy, set;
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cpy = count / BITS_PER_BYTE;
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set = (nfdt->max_fds - count) / BITS_PER_BYTE;
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memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
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memset((char *)nfdt->open_fds + cpy, 0, set);
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memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
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memset((char *)nfdt->close_on_exec + cpy, 0, set);
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cpy = BITBIT_SIZE(count);
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set = BITBIT_SIZE(nfdt->max_fds) - cpy;
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memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
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memset((char *)nfdt->full_fds_bits + cpy, 0, set);
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}
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/*
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* Copy all file descriptors from the old table to the new, expanded table and
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* clear the extra space. Called with the files spinlock held for write.
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*/
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static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
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{
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unsigned int cpy, set;
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BUG_ON(nfdt->max_fds < ofdt->max_fds);
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cpy = ofdt->max_fds * sizeof(struct file *);
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set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
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memcpy(nfdt->fd, ofdt->fd, cpy);
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memset((char *)nfdt->fd + cpy, 0, set);
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copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
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}
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static struct fdtable * alloc_fdtable(unsigned int nr)
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{
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struct fdtable *fdt;
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void *data;
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/*
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* Figure out how many fds we actually want to support in this fdtable.
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* Allocation steps are keyed to the size of the fdarray, since it
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* grows far faster than any of the other dynamic data. We try to fit
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* the fdarray into comfortable page-tuned chunks: starting at 1024B
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* and growing in powers of two from there on.
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*/
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nr /= (1024 / sizeof(struct file *));
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nr = roundup_pow_of_two(nr + 1);
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nr *= (1024 / sizeof(struct file *));
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/*
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* Note that this can drive nr *below* what we had passed if sysctl_nr_open
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* had been set lower between the check in expand_files() and here. Deal
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* with that in caller, it's cheaper that way.
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*
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* We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
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* bitmaps handling below becomes unpleasant, to put it mildly...
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*/
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if (unlikely(nr > sysctl_nr_open))
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nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
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fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
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if (!fdt)
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goto out;
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fdt->max_fds = nr;
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data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
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if (!data)
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goto out_fdt;
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fdt->fd = data;
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data = kvmalloc(max_t(size_t,
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2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
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GFP_KERNEL_ACCOUNT);
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if (!data)
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goto out_arr;
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fdt->open_fds = data;
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data += nr / BITS_PER_BYTE;
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fdt->close_on_exec = data;
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data += nr / BITS_PER_BYTE;
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fdt->full_fds_bits = data;
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return fdt;
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out_arr:
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kvfree(fdt->fd);
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out_fdt:
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kfree(fdt);
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out:
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return NULL;
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}
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/*
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* Expand the file descriptor table.
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* This function will allocate a new fdtable and both fd array and fdset, of
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* the given size.
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* Return <0 error code on error; 1 on successful completion.
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* The files->file_lock should be held on entry, and will be held on exit.
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*/
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static int expand_fdtable(struct files_struct *files, unsigned int nr)
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__releases(files->file_lock)
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__acquires(files->file_lock)
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{
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struct fdtable *new_fdt, *cur_fdt;
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spin_unlock(&files->file_lock);
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new_fdt = alloc_fdtable(nr);
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/* make sure all __fd_install() have seen resize_in_progress
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* or have finished their rcu_read_lock_sched() section.
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*/
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if (atomic_read(&files->count) > 1)
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synchronize_rcu();
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spin_lock(&files->file_lock);
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if (!new_fdt)
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return -ENOMEM;
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/*
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* extremely unlikely race - sysctl_nr_open decreased between the check in
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* caller and alloc_fdtable(). Cheaper to catch it here...
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*/
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if (unlikely(new_fdt->max_fds <= nr)) {
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__free_fdtable(new_fdt);
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return -EMFILE;
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}
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cur_fdt = files_fdtable(files);
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BUG_ON(nr < cur_fdt->max_fds);
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copy_fdtable(new_fdt, cur_fdt);
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rcu_assign_pointer(files->fdt, new_fdt);
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if (cur_fdt != &files->fdtab)
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call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
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/* coupled with smp_rmb() in __fd_install() */
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smp_wmb();
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return 1;
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}
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/*
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* Expand files.
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* This function will expand the file structures, if the requested size exceeds
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* the current capacity and there is room for expansion.
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* Return <0 error code on error; 0 when nothing done; 1 when files were
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* expanded and execution may have blocked.
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* The files->file_lock should be held on entry, and will be held on exit.
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*/
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static int expand_files(struct files_struct *files, unsigned int nr)
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__releases(files->file_lock)
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__acquires(files->file_lock)
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{
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struct fdtable *fdt;
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int expanded = 0;
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repeat:
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fdt = files_fdtable(files);
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/* Do we need to expand? */
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if (nr < fdt->max_fds)
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return expanded;
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/* Can we expand? */
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if (nr >= sysctl_nr_open)
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return -EMFILE;
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if (unlikely(files->resize_in_progress)) {
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spin_unlock(&files->file_lock);
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expanded = 1;
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wait_event(files->resize_wait, !files->resize_in_progress);
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spin_lock(&files->file_lock);
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goto repeat;
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}
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/* All good, so we try */
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files->resize_in_progress = true;
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expanded = expand_fdtable(files, nr);
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files->resize_in_progress = false;
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wake_up_all(&files->resize_wait);
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return expanded;
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}
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static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
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{
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__set_bit(fd, fdt->close_on_exec);
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}
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static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
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{
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if (test_bit(fd, fdt->close_on_exec))
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__clear_bit(fd, fdt->close_on_exec);
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}
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static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
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{
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__set_bit(fd, fdt->open_fds);
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fd /= BITS_PER_LONG;
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if (!~fdt->open_fds[fd])
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__set_bit(fd, fdt->full_fds_bits);
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}
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static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
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{
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__clear_bit(fd, fdt->open_fds);
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__clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
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}
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static unsigned int count_open_files(struct fdtable *fdt)
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{
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unsigned int size = fdt->max_fds;
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unsigned int i;
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/* Find the last open fd */
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for (i = size / BITS_PER_LONG; i > 0; ) {
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if (fdt->open_fds[--i])
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break;
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}
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i = (i + 1) * BITS_PER_LONG;
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return i;
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}
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/*
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* Allocate a new files structure and copy contents from the
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* passed in files structure.
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* errorp will be valid only when the returned files_struct is NULL.
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*/
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struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
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{
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struct files_struct *newf;
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struct file **old_fds, **new_fds;
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unsigned int open_files, i;
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struct fdtable *old_fdt, *new_fdt;
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*errorp = -ENOMEM;
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newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
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if (!newf)
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goto out;
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atomic_set(&newf->count, 1);
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spin_lock_init(&newf->file_lock);
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newf->resize_in_progress = false;
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init_waitqueue_head(&newf->resize_wait);
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newf->next_fd = 0;
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new_fdt = &newf->fdtab;
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new_fdt->max_fds = NR_OPEN_DEFAULT;
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new_fdt->close_on_exec = newf->close_on_exec_init;
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new_fdt->open_fds = newf->open_fds_init;
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new_fdt->full_fds_bits = newf->full_fds_bits_init;
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new_fdt->fd = &newf->fd_array[0];
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|
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spin_lock(&oldf->file_lock);
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old_fdt = files_fdtable(oldf);
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open_files = count_open_files(old_fdt);
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|
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/*
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* Check whether we need to allocate a larger fd array and fd set.
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*/
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while (unlikely(open_files > new_fdt->max_fds)) {
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spin_unlock(&oldf->file_lock);
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|
|
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if (new_fdt != &newf->fdtab)
|
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__free_fdtable(new_fdt);
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|
|
|
new_fdt = alloc_fdtable(open_files - 1);
|
|
if (!new_fdt) {
|
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*errorp = -ENOMEM;
|
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goto out_release;
|
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}
|
|
|
|
/* beyond sysctl_nr_open; nothing to do */
|
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if (unlikely(new_fdt->max_fds < open_files)) {
|
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__free_fdtable(new_fdt);
|
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*errorp = -EMFILE;
|
|
goto out_release;
|
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}
|
|
|
|
/*
|
|
* Reacquire the oldf lock and a pointer to its fd table
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* who knows it may have a new bigger fd table. We need
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* the latest pointer.
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*/
|
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spin_lock(&oldf->file_lock);
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old_fdt = files_fdtable(oldf);
|
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open_files = count_open_files(old_fdt);
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}
|
|
|
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copy_fd_bitmaps(new_fdt, old_fdt, open_files);
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|
|
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old_fds = old_fdt->fd;
|
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new_fds = new_fdt->fd;
|
|
|
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for (i = open_files; i != 0; i--) {
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struct file *f = *old_fds++;
|
|
if (f) {
|
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get_file(f);
|
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} else {
|
|
/*
|
|
* The fd may be claimed in the fd bitmap but not yet
|
|
* instantiated in the files array if a sibling thread
|
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* is partway through open(). So make sure that this
|
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* fd is available to the new process.
|
|
*/
|
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__clear_open_fd(open_files - i, new_fdt);
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}
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rcu_assign_pointer(*new_fds++, f);
|
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}
|
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spin_unlock(&oldf->file_lock);
|
|
|
|
/* clear the remainder */
|
|
memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
|
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|
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rcu_assign_pointer(newf->fdt, new_fdt);
|
|
|
|
return newf;
|
|
|
|
out_release:
|
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kmem_cache_free(files_cachep, newf);
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out:
|
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return NULL;
|
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}
|
|
|
|
static struct fdtable *close_files(struct files_struct * files)
|
|
{
|
|
/*
|
|
* It is safe to dereference the fd table without RCU or
|
|
* ->file_lock because this is the last reference to the
|
|
* files structure.
|
|
*/
|
|
struct fdtable *fdt = rcu_dereference_raw(files->fdt);
|
|
unsigned int i, j = 0;
|
|
|
|
for (;;) {
|
|
unsigned long set;
|
|
i = j * BITS_PER_LONG;
|
|
if (i >= fdt->max_fds)
|
|
break;
|
|
set = fdt->open_fds[j++];
|
|
while (set) {
|
|
if (set & 1) {
|
|
struct file * file = xchg(&fdt->fd[i], NULL);
|
|
if (file) {
|
|
filp_close(file, files);
|
|
cond_resched();
|
|
}
|
|
}
|
|
i++;
|
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set >>= 1;
|
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}
|
|
}
|
|
|
|
return fdt;
|
|
}
|
|
|
|
struct files_struct *get_files_struct(struct task_struct *task)
|
|
{
|
|
struct files_struct *files;
|
|
|
|
task_lock(task);
|
|
files = task->files;
|
|
if (files)
|
|
atomic_inc(&files->count);
|
|
task_unlock(task);
|
|
|
|
return files;
|
|
}
|
|
|
|
void put_files_struct(struct files_struct *files)
|
|
{
|
|
if (atomic_dec_and_test(&files->count)) {
|
|
struct fdtable *fdt = close_files(files);
|
|
|
|
/* free the arrays if they are not embedded */
|
|
if (fdt != &files->fdtab)
|
|
__free_fdtable(fdt);
|
|
kmem_cache_free(files_cachep, files);
|
|
}
|
|
}
|
|
|
|
void reset_files_struct(struct files_struct *files)
|
|
{
|
|
struct task_struct *tsk = current;
|
|
struct files_struct *old;
|
|
|
|
old = tsk->files;
|
|
task_lock(tsk);
|
|
tsk->files = files;
|
|
task_unlock(tsk);
|
|
put_files_struct(old);
|
|
}
|
|
|
|
void exit_files(struct task_struct *tsk)
|
|
{
|
|
struct files_struct * files = tsk->files;
|
|
|
|
if (files) {
|
|
task_lock(tsk);
|
|
tsk->files = NULL;
|
|
task_unlock(tsk);
|
|
put_files_struct(files);
|
|
}
|
|
}
|
|
|
|
struct files_struct init_files = {
|
|
.count = ATOMIC_INIT(1),
|
|
.fdt = &init_files.fdtab,
|
|
.fdtab = {
|
|
.max_fds = NR_OPEN_DEFAULT,
|
|
.fd = &init_files.fd_array[0],
|
|
.close_on_exec = init_files.close_on_exec_init,
|
|
.open_fds = init_files.open_fds_init,
|
|
.full_fds_bits = init_files.full_fds_bits_init,
|
|
},
|
|
.file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
|
|
.resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
|
|
};
|
|
|
|
static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
|
|
{
|
|
unsigned int maxfd = fdt->max_fds;
|
|
unsigned int maxbit = maxfd / BITS_PER_LONG;
|
|
unsigned int bitbit = start / BITS_PER_LONG;
|
|
|
|
bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
|
|
if (bitbit > maxfd)
|
|
return maxfd;
|
|
if (bitbit > start)
|
|
start = bitbit;
|
|
return find_next_zero_bit(fdt->open_fds, maxfd, start);
|
|
}
|
|
|
|
/*
|
|
* allocate a file descriptor, mark it busy.
|
|
*/
|
|
int __alloc_fd(struct files_struct *files,
|
|
unsigned start, unsigned end, unsigned flags)
|
|
{
|
|
unsigned int fd;
|
|
int error;
|
|
struct fdtable *fdt;
|
|
|
|
spin_lock(&files->file_lock);
|
|
repeat:
|
|
fdt = files_fdtable(files);
|
|
fd = start;
|
|
if (fd < files->next_fd)
|
|
fd = files->next_fd;
|
|
|
|
if (fd < fdt->max_fds)
|
|
fd = find_next_fd(fdt, fd);
|
|
|
|
/*
|
|
* N.B. For clone tasks sharing a files structure, this test
|
|
* will limit the total number of files that can be opened.
|
|
*/
|
|
error = -EMFILE;
|
|
if (fd >= end)
|
|
goto out;
|
|
|
|
error = expand_files(files, fd);
|
|
if (error < 0)
|
|
goto out;
|
|
|
|
/*
|
|
* If we needed to expand the fs array we
|
|
* might have blocked - try again.
|
|
*/
|
|
if (error)
|
|
goto repeat;
|
|
|
|
if (start <= files->next_fd)
|
|
files->next_fd = fd + 1;
|
|
|
|
__set_open_fd(fd, fdt);
|
|
if (flags & O_CLOEXEC)
|
|
__set_close_on_exec(fd, fdt);
|
|
else
|
|
__clear_close_on_exec(fd, fdt);
|
|
error = fd;
|
|
#if 1
|
|
/* Sanity check */
|
|
if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
|
|
printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
|
|
rcu_assign_pointer(fdt->fd[fd], NULL);
|
|
}
|
|
#endif
|
|
|
|
out:
|
|
spin_unlock(&files->file_lock);
|
|
return error;
|
|
}
|
|
|
|
static int alloc_fd(unsigned start, unsigned flags)
|
|
{
|
|
return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
|
|
}
|
|
|
|
int get_unused_fd_flags(unsigned flags)
|
|
{
|
|
return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
|
|
}
|
|
EXPORT_SYMBOL(get_unused_fd_flags);
|
|
|
|
static void __put_unused_fd(struct files_struct *files, unsigned int fd)
|
|
{
|
|
struct fdtable *fdt = files_fdtable(files);
|
|
__clear_open_fd(fd, fdt);
|
|
if (fd < files->next_fd)
|
|
files->next_fd = fd;
|
|
}
|
|
|
|
void put_unused_fd(unsigned int fd)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
spin_lock(&files->file_lock);
|
|
__put_unused_fd(files, fd);
|
|
spin_unlock(&files->file_lock);
|
|
}
|
|
|
|
EXPORT_SYMBOL(put_unused_fd);
|
|
|
|
/*
|
|
* Install a file pointer in the fd array.
|
|
*
|
|
* The VFS is full of places where we drop the files lock between
|
|
* setting the open_fds bitmap and installing the file in the file
|
|
* array. At any such point, we are vulnerable to a dup2() race
|
|
* installing a file in the array before us. We need to detect this and
|
|
* fput() the struct file we are about to overwrite in this case.
|
|
*
|
|
* It should never happen - if we allow dup2() do it, _really_ bad things
|
|
* will follow.
|
|
*
|
|
* NOTE: __fd_install() variant is really, really low-level; don't
|
|
* use it unless you are forced to by truly lousy API shoved down
|
|
* your throat. 'files' *MUST* be either current->files or obtained
|
|
* by get_files_struct(current) done by whoever had given it to you,
|
|
* or really bad things will happen. Normally you want to use
|
|
* fd_install() instead.
|
|
*/
|
|
|
|
void __fd_install(struct files_struct *files, unsigned int fd,
|
|
struct file *file)
|
|
{
|
|
struct fdtable *fdt;
|
|
|
|
rcu_read_lock_sched();
|
|
|
|
if (unlikely(files->resize_in_progress)) {
|
|
rcu_read_unlock_sched();
|
|
spin_lock(&files->file_lock);
|
|
fdt = files_fdtable(files);
|
|
BUG_ON(fdt->fd[fd] != NULL);
|
|
rcu_assign_pointer(fdt->fd[fd], file);
|
|
spin_unlock(&files->file_lock);
|
|
return;
|
|
}
|
|
/* coupled with smp_wmb() in expand_fdtable() */
|
|
smp_rmb();
|
|
fdt = rcu_dereference_sched(files->fdt);
|
|
BUG_ON(fdt->fd[fd] != NULL);
|
|
rcu_assign_pointer(fdt->fd[fd], file);
|
|
rcu_read_unlock_sched();
|
|
}
|
|
|
|
void fd_install(unsigned int fd, struct file *file)
|
|
{
|
|
__fd_install(current->files, fd, file);
|
|
}
|
|
|
|
EXPORT_SYMBOL(fd_install);
|
|
|
|
/*
|
|
* The same warnings as for __alloc_fd()/__fd_install() apply here...
|
|
*/
|
|
int __close_fd(struct files_struct *files, unsigned fd)
|
|
{
|
|
struct file *file;
|
|
struct fdtable *fdt;
|
|
|
|
spin_lock(&files->file_lock);
|
|
fdt = files_fdtable(files);
|
|
if (fd >= fdt->max_fds)
|
|
goto out_unlock;
|
|
file = fdt->fd[fd];
|
|
if (!file)
|
|
goto out_unlock;
|
|
rcu_assign_pointer(fdt->fd[fd], NULL);
|
|
__put_unused_fd(files, fd);
|
|
spin_unlock(&files->file_lock);
|
|
return filp_close(file, files);
|
|
|
|
out_unlock:
|
|
spin_unlock(&files->file_lock);
|
|
return -EBADF;
|
|
}
|
|
EXPORT_SYMBOL(__close_fd); /* for ksys_close() */
|
|
|
|
/*
|
|
* variant of __close_fd that gets a ref on the file for later fput.
|
|
* The caller must ensure that filp_close() called on the file, and then
|
|
* an fput().
|
|
*/
|
|
int __close_fd_get_file(unsigned int fd, struct file **res)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct file *file;
|
|
struct fdtable *fdt;
|
|
|
|
spin_lock(&files->file_lock);
|
|
fdt = files_fdtable(files);
|
|
if (fd >= fdt->max_fds)
|
|
goto out_unlock;
|
|
file = fdt->fd[fd];
|
|
if (!file)
|
|
goto out_unlock;
|
|
rcu_assign_pointer(fdt->fd[fd], NULL);
|
|
__put_unused_fd(files, fd);
|
|
spin_unlock(&files->file_lock);
|
|
get_file(file);
|
|
*res = file;
|
|
return 0;
|
|
|
|
out_unlock:
|
|
spin_unlock(&files->file_lock);
|
|
*res = NULL;
|
|
return -ENOENT;
|
|
}
|
|
|
|
void do_close_on_exec(struct files_struct *files)
|
|
{
|
|
unsigned i;
|
|
struct fdtable *fdt;
|
|
|
|
/* exec unshares first */
|
|
spin_lock(&files->file_lock);
|
|
for (i = 0; ; i++) {
|
|
unsigned long set;
|
|
unsigned fd = i * BITS_PER_LONG;
|
|
fdt = files_fdtable(files);
|
|
if (fd >= fdt->max_fds)
|
|
break;
|
|
set = fdt->close_on_exec[i];
|
|
if (!set)
|
|
continue;
|
|
fdt->close_on_exec[i] = 0;
|
|
for ( ; set ; fd++, set >>= 1) {
|
|
struct file *file;
|
|
if (!(set & 1))
|
|
continue;
|
|
file = fdt->fd[fd];
|
|
if (!file)
|
|
continue;
|
|
rcu_assign_pointer(fdt->fd[fd], NULL);
|
|
__put_unused_fd(files, fd);
|
|
spin_unlock(&files->file_lock);
|
|
filp_close(file, files);
|
|
cond_resched();
|
|
spin_lock(&files->file_lock);
|
|
}
|
|
|
|
}
|
|
spin_unlock(&files->file_lock);
|
|
}
|
|
|
|
static struct file *__fget_files(struct files_struct *files, unsigned int fd,
|
|
fmode_t mask, unsigned int refs)
|
|
{
|
|
struct file *file;
|
|
|
|
rcu_read_lock();
|
|
loop:
|
|
file = fcheck_files(files, fd);
|
|
if (file) {
|
|
/* File object ref couldn't be taken.
|
|
* dup2() atomicity guarantee is the reason
|
|
* we loop to catch the new file (or NULL pointer)
|
|
*/
|
|
if (file->f_mode & mask)
|
|
file = NULL;
|
|
else if (!get_file_rcu_many(file, refs))
|
|
goto loop;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return file;
|
|
}
|
|
|
|
static inline struct file *__fget(unsigned int fd, fmode_t mask,
|
|
unsigned int refs)
|
|
{
|
|
return __fget_files(current->files, fd, mask, refs);
|
|
}
|
|
|
|
struct file *fget_many(unsigned int fd, unsigned int refs)
|
|
{
|
|
return __fget(fd, FMODE_PATH, refs);
|
|
}
|
|
|
|
struct file *fget(unsigned int fd)
|
|
{
|
|
return __fget(fd, FMODE_PATH, 1);
|
|
}
|
|
EXPORT_SYMBOL(fget);
|
|
|
|
struct file *fget_raw(unsigned int fd)
|
|
{
|
|
return __fget(fd, 0, 1);
|
|
}
|
|
EXPORT_SYMBOL(fget_raw);
|
|
|
|
struct file *fget_task(struct task_struct *task, unsigned int fd)
|
|
{
|
|
struct file *file = NULL;
|
|
|
|
task_lock(task);
|
|
if (task->files)
|
|
file = __fget_files(task->files, fd, 0, 1);
|
|
task_unlock(task);
|
|
|
|
return file;
|
|
}
|
|
|
|
/*
|
|
* Lightweight file lookup - no refcnt increment if fd table isn't shared.
|
|
*
|
|
* You can use this instead of fget if you satisfy all of the following
|
|
* conditions:
|
|
* 1) You must call fput_light before exiting the syscall and returning control
|
|
* to userspace (i.e. you cannot remember the returned struct file * after
|
|
* returning to userspace).
|
|
* 2) You must not call filp_close on the returned struct file * in between
|
|
* calls to fget_light and fput_light.
|
|
* 3) You must not clone the current task in between the calls to fget_light
|
|
* and fput_light.
|
|
*
|
|
* The fput_needed flag returned by fget_light should be passed to the
|
|
* corresponding fput_light.
|
|
*/
|
|
static unsigned long __fget_light(unsigned int fd, fmode_t mask)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct file *file;
|
|
|
|
if (atomic_read(&files->count) == 1) {
|
|
file = __fcheck_files(files, fd);
|
|
if (!file || unlikely(file->f_mode & mask))
|
|
return 0;
|
|
return (unsigned long)file;
|
|
} else {
|
|
file = __fget(fd, mask, 1);
|
|
if (!file)
|
|
return 0;
|
|
return FDPUT_FPUT | (unsigned long)file;
|
|
}
|
|
}
|
|
unsigned long __fdget(unsigned int fd)
|
|
{
|
|
return __fget_light(fd, FMODE_PATH);
|
|
}
|
|
EXPORT_SYMBOL(__fdget);
|
|
|
|
unsigned long __fdget_raw(unsigned int fd)
|
|
{
|
|
return __fget_light(fd, 0);
|
|
}
|
|
|
|
unsigned long __fdget_pos(unsigned int fd)
|
|
{
|
|
unsigned long v = __fdget(fd);
|
|
struct file *file = (struct file *)(v & ~3);
|
|
|
|
if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
|
|
if (file_count(file) > 1) {
|
|
v |= FDPUT_POS_UNLOCK;
|
|
mutex_lock(&file->f_pos_lock);
|
|
}
|
|
}
|
|
return v;
|
|
}
|
|
|
|
void __f_unlock_pos(struct file *f)
|
|
{
|
|
mutex_unlock(&f->f_pos_lock);
|
|
}
|
|
|
|
/*
|
|
* We only lock f_pos if we have threads or if the file might be
|
|
* shared with another process. In both cases we'll have an elevated
|
|
* file count (done either by fdget() or by fork()).
|
|
*/
|
|
|
|
void set_close_on_exec(unsigned int fd, int flag)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct fdtable *fdt;
|
|
spin_lock(&files->file_lock);
|
|
fdt = files_fdtable(files);
|
|
if (flag)
|
|
__set_close_on_exec(fd, fdt);
|
|
else
|
|
__clear_close_on_exec(fd, fdt);
|
|
spin_unlock(&files->file_lock);
|
|
}
|
|
|
|
bool get_close_on_exec(unsigned int fd)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct fdtable *fdt;
|
|
bool res;
|
|
rcu_read_lock();
|
|
fdt = files_fdtable(files);
|
|
res = close_on_exec(fd, fdt);
|
|
rcu_read_unlock();
|
|
return res;
|
|
}
|
|
|
|
static int do_dup2(struct files_struct *files,
|
|
struct file *file, unsigned fd, unsigned flags)
|
|
__releases(&files->file_lock)
|
|
{
|
|
struct file *tofree;
|
|
struct fdtable *fdt;
|
|
|
|
/*
|
|
* We need to detect attempts to do dup2() over allocated but still
|
|
* not finished descriptor. NB: OpenBSD avoids that at the price of
|
|
* extra work in their equivalent of fget() - they insert struct
|
|
* file immediately after grabbing descriptor, mark it larval if
|
|
* more work (e.g. actual opening) is needed and make sure that
|
|
* fget() treats larval files as absent. Potentially interesting,
|
|
* but while extra work in fget() is trivial, locking implications
|
|
* and amount of surgery on open()-related paths in VFS are not.
|
|
* FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
|
|
* deadlocks in rather amusing ways, AFAICS. All of that is out of
|
|
* scope of POSIX or SUS, since neither considers shared descriptor
|
|
* tables and this condition does not arise without those.
|
|
*/
|
|
fdt = files_fdtable(files);
|
|
tofree = fdt->fd[fd];
|
|
if (!tofree && fd_is_open(fd, fdt))
|
|
goto Ebusy;
|
|
get_file(file);
|
|
rcu_assign_pointer(fdt->fd[fd], file);
|
|
__set_open_fd(fd, fdt);
|
|
if (flags & O_CLOEXEC)
|
|
__set_close_on_exec(fd, fdt);
|
|
else
|
|
__clear_close_on_exec(fd, fdt);
|
|
spin_unlock(&files->file_lock);
|
|
|
|
if (tofree)
|
|
filp_close(tofree, files);
|
|
|
|
return fd;
|
|
|
|
Ebusy:
|
|
spin_unlock(&files->file_lock);
|
|
return -EBUSY;
|
|
}
|
|
|
|
int replace_fd(unsigned fd, struct file *file, unsigned flags)
|
|
{
|
|
int err;
|
|
struct files_struct *files = current->files;
|
|
|
|
if (!file)
|
|
return __close_fd(files, fd);
|
|
|
|
if (fd >= rlimit(RLIMIT_NOFILE))
|
|
return -EBADF;
|
|
|
|
spin_lock(&files->file_lock);
|
|
err = expand_files(files, fd);
|
|
if (unlikely(err < 0))
|
|
goto out_unlock;
|
|
return do_dup2(files, file, fd, flags);
|
|
|
|
out_unlock:
|
|
spin_unlock(&files->file_lock);
|
|
return err;
|
|
}
|
|
|
|
static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
|
|
{
|
|
int err = -EBADF;
|
|
struct file *file;
|
|
struct files_struct *files = current->files;
|
|
|
|
if ((flags & ~O_CLOEXEC) != 0)
|
|
return -EINVAL;
|
|
|
|
if (unlikely(oldfd == newfd))
|
|
return -EINVAL;
|
|
|
|
if (newfd >= rlimit(RLIMIT_NOFILE))
|
|
return -EBADF;
|
|
|
|
spin_lock(&files->file_lock);
|
|
err = expand_files(files, newfd);
|
|
file = fcheck(oldfd);
|
|
if (unlikely(!file))
|
|
goto Ebadf;
|
|
if (unlikely(err < 0)) {
|
|
if (err == -EMFILE)
|
|
goto Ebadf;
|
|
goto out_unlock;
|
|
}
|
|
return do_dup2(files, file, newfd, flags);
|
|
|
|
Ebadf:
|
|
err = -EBADF;
|
|
out_unlock:
|
|
spin_unlock(&files->file_lock);
|
|
return err;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
|
|
{
|
|
return ksys_dup3(oldfd, newfd, flags);
|
|
}
|
|
|
|
SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
|
|
{
|
|
if (unlikely(newfd == oldfd)) { /* corner case */
|
|
struct files_struct *files = current->files;
|
|
int retval = oldfd;
|
|
|
|
rcu_read_lock();
|
|
if (!fcheck_files(files, oldfd))
|
|
retval = -EBADF;
|
|
rcu_read_unlock();
|
|
return retval;
|
|
}
|
|
return ksys_dup3(oldfd, newfd, 0);
|
|
}
|
|
|
|
int ksys_dup(unsigned int fildes)
|
|
{
|
|
int ret = -EBADF;
|
|
struct file *file = fget_raw(fildes);
|
|
|
|
if (file) {
|
|
ret = get_unused_fd_flags(0);
|
|
if (ret >= 0)
|
|
fd_install(ret, file);
|
|
else
|
|
fput(file);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
SYSCALL_DEFINE1(dup, unsigned int, fildes)
|
|
{
|
|
return ksys_dup(fildes);
|
|
}
|
|
|
|
int f_dupfd(unsigned int from, struct file *file, unsigned flags)
|
|
{
|
|
int err;
|
|
if (from >= rlimit(RLIMIT_NOFILE))
|
|
return -EINVAL;
|
|
err = alloc_fd(from, flags);
|
|
if (err >= 0) {
|
|
get_file(file);
|
|
fd_install(err, file);
|
|
}
|
|
return err;
|
|
}
|
|
|
|
int iterate_fd(struct files_struct *files, unsigned n,
|
|
int (*f)(const void *, struct file *, unsigned),
|
|
const void *p)
|
|
{
|
|
struct fdtable *fdt;
|
|
int res = 0;
|
|
if (!files)
|
|
return 0;
|
|
spin_lock(&files->file_lock);
|
|
for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
|
|
struct file *file;
|
|
file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
|
|
if (!file)
|
|
continue;
|
|
res = f(p, file, n);
|
|
if (res)
|
|
break;
|
|
}
|
|
spin_unlock(&files->file_lock);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(iterate_fd);
|