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![Zqiang](/assets/img/avatar_default.png)
The syzbot reported a memleak as follows:
BUG: memory leak
unreferenced object 0xffff888101b41d00 (size 120):
comm "kworker/u4:0", pid 8, jiffies 4294944270 (age 12.780s)
backtrace:
[<ffffffff8125dc56>] alloc_pid+0x66/0x560
[<ffffffff81226405>] copy_process+0x1465/0x25e0
[<ffffffff81227943>] kernel_clone+0xf3/0x670
[<ffffffff812281a1>] kernel_thread+0x61/0x80
[<ffffffff81253464>] call_usermodehelper_exec_work
[<ffffffff81253464>] call_usermodehelper_exec_work+0xc4/0x120
[<ffffffff812591c9>] process_one_work+0x2c9/0x600
[<ffffffff81259ab9>] worker_thread+0x59/0x5d0
[<ffffffff812611c8>] kthread+0x178/0x1b0
[<ffffffff8100227f>] ret_from_fork+0x1f/0x30
unreferenced object 0xffff888110ef5c00 (size 232):
comm "kworker/u4:0", pid 8414, jiffies 4294944270 (age 12.780s)
backtrace:
[<ffffffff8154a0cf>] kmem_cache_zalloc
[<ffffffff8154a0cf>] __alloc_file+0x1f/0xf0
[<ffffffff8154a809>] alloc_empty_file+0x69/0x120
[<ffffffff8154a8f3>] alloc_file+0x33/0x1b0
[<ffffffff8154ab22>] alloc_file_pseudo+0xb2/0x140
[<ffffffff81559218>] create_pipe_files+0x138/0x2e0
[<ffffffff8126c793>] umd_setup+0x33/0x220
[<ffffffff81253574>] call_usermodehelper_exec_async+0xb4/0x1b0
[<ffffffff8100227f>] ret_from_fork+0x1f/0x30
After the UMD process exits, the pipe_to_umh/pipe_from_umh and
tgid need to be released.
Fixes: d71fa5c976
("bpf: Add kernel module with user mode driver that populates bpffs.")
Reported-by: syzbot+44908bb56d2bfe56b28e@syzkaller.appspotmail.com
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210317030915.2865-1-qiang.zhang@windriver.com
191 lines
4.3 KiB
C
191 lines
4.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* umd - User mode driver support
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*/
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#include <linux/shmem_fs.h>
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#include <linux/pipe_fs_i.h>
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#include <linux/mount.h>
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#include <linux/fs_struct.h>
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#include <linux/task_work.h>
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#include <linux/usermode_driver.h>
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static struct vfsmount *blob_to_mnt(const void *data, size_t len, const char *name)
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{
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struct file_system_type *type;
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struct vfsmount *mnt;
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struct file *file;
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ssize_t written;
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loff_t pos = 0;
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type = get_fs_type("tmpfs");
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if (!type)
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return ERR_PTR(-ENODEV);
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mnt = kern_mount(type);
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put_filesystem(type);
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if (IS_ERR(mnt))
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return mnt;
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file = file_open_root(mnt->mnt_root, mnt, name, O_CREAT | O_WRONLY, 0700);
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if (IS_ERR(file)) {
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mntput(mnt);
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return ERR_CAST(file);
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}
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written = kernel_write(file, data, len, &pos);
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if (written != len) {
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int err = written;
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if (err >= 0)
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err = -ENOMEM;
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filp_close(file, NULL);
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mntput(mnt);
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return ERR_PTR(err);
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}
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fput(file);
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/* Flush delayed fput so exec can open the file read-only */
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flush_delayed_fput();
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task_work_run();
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return mnt;
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}
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/**
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* umd_load_blob - Remember a blob of bytes for fork_usermode_driver
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* @info: information about usermode driver
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* @data: a blob of bytes that can be executed as a file
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* @len: The lentgh of the blob
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*
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*/
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int umd_load_blob(struct umd_info *info, const void *data, size_t len)
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{
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struct vfsmount *mnt;
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if (WARN_ON_ONCE(info->wd.dentry || info->wd.mnt))
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return -EBUSY;
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mnt = blob_to_mnt(data, len, info->driver_name);
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if (IS_ERR(mnt))
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return PTR_ERR(mnt);
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info->wd.mnt = mnt;
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info->wd.dentry = mnt->mnt_root;
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return 0;
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}
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EXPORT_SYMBOL_GPL(umd_load_blob);
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/**
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* umd_unload_blob - Disassociate @info from a previously loaded blob
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* @info: information about usermode driver
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*
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*/
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int umd_unload_blob(struct umd_info *info)
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{
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if (WARN_ON_ONCE(!info->wd.mnt ||
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!info->wd.dentry ||
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info->wd.mnt->mnt_root != info->wd.dentry))
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return -EINVAL;
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kern_unmount(info->wd.mnt);
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info->wd.mnt = NULL;
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info->wd.dentry = NULL;
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return 0;
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}
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EXPORT_SYMBOL_GPL(umd_unload_blob);
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static int umd_setup(struct subprocess_info *info, struct cred *new)
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{
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struct umd_info *umd_info = info->data;
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struct file *from_umh[2];
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struct file *to_umh[2];
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int err;
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/* create pipe to send data to umh */
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err = create_pipe_files(to_umh, 0);
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if (err)
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return err;
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err = replace_fd(0, to_umh[0], 0);
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fput(to_umh[0]);
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if (err < 0) {
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fput(to_umh[1]);
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return err;
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}
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/* create pipe to receive data from umh */
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err = create_pipe_files(from_umh, 0);
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if (err) {
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fput(to_umh[1]);
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replace_fd(0, NULL, 0);
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return err;
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}
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err = replace_fd(1, from_umh[1], 0);
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fput(from_umh[1]);
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if (err < 0) {
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fput(to_umh[1]);
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replace_fd(0, NULL, 0);
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fput(from_umh[0]);
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return err;
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}
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set_fs_pwd(current->fs, &umd_info->wd);
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umd_info->pipe_to_umh = to_umh[1];
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umd_info->pipe_from_umh = from_umh[0];
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umd_info->tgid = get_pid(task_tgid(current));
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return 0;
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}
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static void umd_cleanup(struct subprocess_info *info)
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{
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struct umd_info *umd_info = info->data;
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/* cleanup if umh_setup() was successful but exec failed */
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if (info->retval)
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umd_cleanup_helper(umd_info);
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}
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/**
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* umd_cleanup_helper - release the resources which were allocated in umd_setup
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* @info: information about usermode driver
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*/
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void umd_cleanup_helper(struct umd_info *info)
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{
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fput(info->pipe_to_umh);
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fput(info->pipe_from_umh);
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put_pid(info->tgid);
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info->tgid = NULL;
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}
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EXPORT_SYMBOL_GPL(umd_cleanup_helper);
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/**
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* fork_usermode_driver - fork a usermode driver
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* @info: information about usermode driver (shouldn't be NULL)
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*
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* Returns either negative error or zero which indicates success in
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* executing a usermode driver. In such case 'struct umd_info *info'
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* is populated with two pipes and a tgid of the process. The caller is
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* responsible for health check of the user process, killing it via
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* tgid, and closing the pipes when user process is no longer needed.
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*/
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int fork_usermode_driver(struct umd_info *info)
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{
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struct subprocess_info *sub_info;
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const char *argv[] = { info->driver_name, NULL };
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int err;
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if (WARN_ON_ONCE(info->tgid))
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return -EBUSY;
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err = -ENOMEM;
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sub_info = call_usermodehelper_setup(info->driver_name,
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(char **)argv, NULL, GFP_KERNEL,
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umd_setup, umd_cleanup, info);
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if (!sub_info)
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goto out;
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err = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
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out:
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return err;
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}
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EXPORT_SYMBOL_GPL(fork_usermode_driver);
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