linux-stable/kernel/kmod.c

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/*
kmod: split out umh code into its own file Patch series "kmod: few code cleanups to split out umh code" The usermode helper has a provenance from the old usb code which first required a usermode helper. Eventually this was shoved into kmod.c and the kernel's modprobe calls was converted over eventually to share the same code. Over time the list of usermode helpers in the kernel has grown -- so kmod is just but one user of the API. This series is a simple logical cleanup which acknowledges the code evolution of the usermode helper and shoves the UMH API into its own dedicated file. This way users of the API can later just include umh.h instead of kmod.h. Note despite the diff state the first patch really is just a code shove, no functional changes are done there. I did use git format-patch -M to generate the patch, but in the end the split was not enough for git to consider it a rename hence the large diffstat. I've put this through 0-day and it gives me their machine compilation blessings with all tests as OK. This patch (of 4): There's a slew of usermode helper users and kmod is just one of them. Split out the usermode helper code into its own file to keep the logic and focus split up. This change provides no functional changes. Link: http://lkml.kernel.org/r/20170810180618.22457-2-mcgrof@kernel.org Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com> Cc: Jessica Yu <jeyu@redhat.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Michal Marek <mmarek@suse.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Miroslav Benes <mbenes@suse.cz> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Matt Redfearn <matt.redfearn@imgtec.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Colin Ian King <colin.king@canonical.com> Cc: Daniel Mentz <danielmentz@google.com> Cc: David Binderman <dcb314@hotmail.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-08 23:17:00 +00:00
* kmod - the kernel module loader
*/
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/binfmts.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/completion.h>
#include <linux/cred.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/kernel.h>
#include <linux/init.h>
[PATCH] Support piping into commands in /proc/sys/kernel/core_pattern Using the infrastructure created in previous patches implement support to pipe core dumps into programs. This is done by overloading the existing core_pattern sysctl with a new syntax: |program When the first character of the pattern is a '|' the kernel will instead threat the rest of the pattern as a command to run. The core dump will be written to the standard input of that program instead of to a file. This is useful for having automatic core dump analysis without filling up disks. The program can do some simple analysis and save only a summary of the core dump. The core dump proces will run with the privileges and in the name space of the process that caused the core dump. I also increased the core pattern size to 128 bytes so that longer command lines fit. Most of the changes comes from allowing core dumps without seeks. They are fairly straight forward though. One small incompatibility is that if someone had a core pattern previously that started with '|' they will get suddenly new behaviour. I think that's unlikely to be a real problem though. Additional background: > Very nice, do you happen to have a program that can accept this kind of > input for crash dumps? I'm guessing that the embedded people will > really want this functionality. I had a cheesy demo/prototype. Basically it wrote the dump to a file again, ran gdb on it to get a backtrace and wrote the summary to a shared directory. Then there was a simple CGI script to generate a "top 10" crashes HTML listing. Unfortunately this still had the disadvantage to needing full disk space for a dump except for deleting it afterwards (in fact it was worse because over the pipe holes didn't work so if you have a holey address map it would require more space). Fortunately gdb seems to be happy to handle /proc/pid/fd/xxx input pipes as cores (at least it worked with zsh's =(cat core) syntax), so it would be likely possible to do it without temporary space with a simple wrapper that calls it in the right way. I ran out of time before doing that though. The demo prototype scripts weren't very good. If there is really interest I can dig them out (they are currently on a laptop disk on the desk with the laptop itself being in service), but I would recommend to rewrite them for any serious application of this and fix the disk space problem. Also to be really useful it should probably find a way to automatically fetch the debuginfos (I cheated and just installed them in advance). If nobody else does it I can probably do the rewrite myself again at some point. My hope at some point was that desktops would support it in their builtin crash reporters, but at least the KDE people I talked too seemed to be happy with their user space only solution. Alan sayeth: I don't believe that piping as such as neccessarily the right model, but the ability to intercept and processes core dumps from user space is asked for by many enterprise users as well. They want to know about, capture, analyse and process core dumps, often centrally and in automated form. [akpm@osdl.org: loff_t != unsigned long] Signed-off-by: Andi Kleen <ak@suse.de> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-01 06:29:28 +00:00
#include <linux/resource.h>
#include <linux/notifier.h>
#include <linux/suspend.h>
PM / Sleep: Fix freezer failures due to racy usermodehelper_is_disabled() Commit a144c6a (PM: Print a warning if firmware is requested when tasks are frozen) introduced usermodehelper_is_disabled() to warn and exit immediately if firmware is requested when usermodehelpers are disabled. However, it is racy. Consider the following scenario, currently used in drivers/base/firmware_class.c: ... if (usermodehelper_is_disabled()) goto out; /* Do actual work */ ... out: return err; Nothing prevents someone from disabling usermodehelpers just after the check in the 'if' condition, which means that it is quite possible to try doing the "actual work" with usermodehelpers disabled, leading to undesirable consequences. In particular, this race condition in _request_firmware() causes task freezing failures whenever suspend/hibernation is in progress because, it wrongly waits to get the firmware/microcode image from userspace when actually the usermodehelpers are disabled or userspace has been frozen. Some of the example scenarios that cause freezing failures due to this race are those that depend on userspace via request_firmware(), such as x86 microcode module initialization and microcode image reload. Previous discussions about this issue can be found at: http://thread.gmane.org/gmane.linux.kernel/1198291/focus=1200591 This patch adds proper synchronization to fix this issue. It is to be noted that this patchset fixes the freezing failures but doesn't remove the warnings. IOW, it does not attempt to add explicit synchronization to x86 microcode driver to avoid requesting microcode image at inopportune moments. Because, the warnings were introduced to highlight such cases, in the first place. And we need not silence the warnings, since we take care of the *real* problem (freezing failure) and hence, after that, the warnings are pretty harmless anyway. Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-12-09 22:36:36 +00:00
#include <linux/rwsem.h>
#include <linux/ptrace.h>
#include <linux/async.h>
#include <linux/uaccess.h>
tracing/events: Add module tracepoints Add trace points to trace module_load, module_free, module_get, module_put and module_request, and use trace_event facility to get the trace output. Here's the sample output: TASK-PID CPU# TIMESTAMP FUNCTION | | | | | <...>-42 [000] 1.758380: module_request: fb0 wait=1 call_site=fb_open ... <...>-60 [000] 3.269403: module_load: scsi_wait_scan <...>-60 [000] 3.269432: module_put: scsi_wait_scan call_site=sys_init_module refcnt=0 <...>-61 [001] 3.273168: module_free: scsi_wait_scan ... <...>-1021 [000] 13.836081: module_load: sunrpc <...>-1021 [000] 13.840589: module_put: sunrpc call_site=sys_init_module refcnt=-1 <...>-1027 [000] 13.848098: module_get: sunrpc call_site=try_module_get refcnt=0 <...>-1027 [000] 13.848308: module_get: sunrpc call_site=get_filesystem refcnt=1 <...>-1027 [000] 13.848692: module_put: sunrpc call_site=put_filesystem refcnt=0 ... modprobe-2587 [001] 1088.437213: module_load: trace_events_sample F modprobe-2587 [001] 1088.437786: module_put: trace_events_sample call_site=sys_init_module refcnt=0 Note: - the taints flag can be 'F', 'C' and/or 'P' if mod->taints != 0 - the module refcnt is percpu, so it can be negative in a specific cpu Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Rusty Russell <rusty@rustcorp.com.au> LKML-Reference: <4A891B3C.5030608@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-08-17 08:56:28 +00:00
#include <trace/events/module.h>
kmod: reduce atomic operations on kmod_concurrent and simplify When checking if we want to allow a kmod thread to kick off we increment, then read to see if we should enable a thread. If we were over the allowed limit limit we decrement. Splitting the increment far apart from decrement means there could be a time where two increments happen potentially giving a false failure on a thread which should have been allowed. CPU1 CPU2 atomic_inc() atomic_inc() atomic_read() atomic_read() atomic_dec() atomic_dec() In this case a read on CPU1 gets the atomic_inc()'s and we could negate it from getting a kmod thread. We could try to prevent this with a lock or preemption but that is overkill. We can fix by reducing the number of atomic operations. We do this by inverting the logic of of the enabler, instead of incrementing kmod_concurrent as we get new kmod users, define the variable kmod_concurrent_max as the max number of currently allowed kmod users and as we get new kmod users just decrement it if its still positive. This combines the dec and read in one atomic operation. In this case we no longer get the same false failure: CPU1 CPU2 atomic_dec_if_positive() atomic_dec_if_positive() atomic_inc() atomic_inc() The number of threads is computed at init, and since the current computation of kmod_concurrent includes the thread count we can avoid setting kmod_concurrent_max later in boot through an init call by simply sticking to 50 as the kmod_concurrent_max. The assumption here is a system with modules must at least have ~16 MiB of RAM. Suggested-by: Petr Mladek <pmladek@suse.com> Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
2017-06-23 19:19:12 +00:00
/*
* Assuming:
*
* threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
* (u64) THREAD_SIZE * 8UL);
*
* If you need less than 50 threads would mean we're dealing with systems
* smaller than 3200 pages. This assumes you are capable of having ~13M memory,
* and this would only be an upper limit, after which the OOM killer would take
* effect. Systems like these are very unlikely if modules are enabled.
kmod: reduce atomic operations on kmod_concurrent and simplify When checking if we want to allow a kmod thread to kick off we increment, then read to see if we should enable a thread. If we were over the allowed limit limit we decrement. Splitting the increment far apart from decrement means there could be a time where two increments happen potentially giving a false failure on a thread which should have been allowed. CPU1 CPU2 atomic_inc() atomic_inc() atomic_read() atomic_read() atomic_dec() atomic_dec() In this case a read on CPU1 gets the atomic_inc()'s and we could negate it from getting a kmod thread. We could try to prevent this with a lock or preemption but that is overkill. We can fix by reducing the number of atomic operations. We do this by inverting the logic of of the enabler, instead of incrementing kmod_concurrent as we get new kmod users, define the variable kmod_concurrent_max as the max number of currently allowed kmod users and as we get new kmod users just decrement it if its still positive. This combines the dec and read in one atomic operation. In this case we no longer get the same false failure: CPU1 CPU2 atomic_dec_if_positive() atomic_dec_if_positive() atomic_inc() atomic_inc() The number of threads is computed at init, and since the current computation of kmod_concurrent includes the thread count we can avoid setting kmod_concurrent_max later in boot through an init call by simply sticking to 50 as the kmod_concurrent_max. The assumption here is a system with modules must at least have ~16 MiB of RAM. Suggested-by: Petr Mladek <pmladek@suse.com> Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
2017-06-23 19:19:12 +00:00
*/
#define MAX_KMOD_CONCURRENT 50
static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT);
kmod: throttle kmod thread limit If we reach the limit of modprobe_limit threads running the next request_module() call will fail. The original reason for adding a kill was to do away with possible issues with in old circumstances which would create a recursive series of request_module() calls. We can do better than just be super aggressive and reject calls once we've reached the limit by simply making pending callers wait until the threshold has been reduced, and then throttling them in, one by one. This throttling enables requests over the kmod concurrent limit to be processed once a pending request completes. Only the first item queued up to wait is woken up. The assumption here is once a task is woken it will have no other option to also kick the queue to check if there are more pending tasks -- regardless of whether or not it was successful. By throttling and processing only max kmod concurrent tasks we ensure we avoid unexpected fatal request_module() calls, and we keep memory consumption on module loading to a minimum. With x86_64 qemu, with 4 cores, 4 GiB of RAM it takes the following run time to run both tests: time ./kmod.sh -t 0008 real 0m16.366s user 0m0.883s sys 0m8.916s time ./kmod.sh -t 0009 real 0m50.803s user 0m0.791s sys 0m9.852s Link: http://lkml.kernel.org/r/20170628223155.26472-4-mcgrof@kernel.org Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Cc: Jessica Yu <jeyu@redhat.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Michal Marek <mmarek@suse.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-14 21:50:11 +00:00
static DECLARE_WAIT_QUEUE_HEAD(kmod_wq);
kmod: fix wait on recursive loop Recursive loops with module loading were previously handled in kmod by restricting the number of modprobe calls to 50 and if that limit was breached request_module() would return an error and a user would see the following on their kernel dmesg: request_module: runaway loop modprobe binfmt-464c Starting init:/sbin/init exists but couldn't execute it (error -8) This issue could happen for instance when a 64-bit kernel boots a 32-bit userspace on some architectures and has no 32-bit binary format hanlders. This is visible, for instance, when a CONFIG_MODULES enabled 64-bit MIPS kernel boots a into o32 root filesystem and the binfmt handler for o32 binaries is not built-in. After commit 6d7964a722af ("kmod: throttle kmod thread limit") we now don't have any visible signs of an error and the kernel just waits for the loop to end somehow. Although this *particular* recursive loop could also be addressed by doing a sanity check on search_binary_handler() and disallowing a modular binfmt to be required for modprobe, a generic solution for any recursive kernel kmod issues is still needed. This should catch these loops. We can investigate each loop and address each one separately as they come in, this however puts a stop gap for them as before. Link: http://lkml.kernel.org/r/20170809234635.13443-3-mcgrof@kernel.org Fixes: 6d7964a722af ("kmod: throttle kmod thread limit") Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reported-by: Matt Redfearn <matt.redfearn@imgtec.com> Tested-by: Matt Redfearn <matt.redfearn@imgetc.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Colin Ian King <colin.king@canonical.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Daniel Mentz <danielmentz@google.com> Cc: David Binderman <dcb314@hotmail.com> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jessica Yu <jeyu@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Michal Marek <mmarek@suse.com> Cc: Miroslav Benes <mbenes@suse.cz> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-08-18 22:15:58 +00:00
/*
* This is a restriction on having *all* MAX_KMOD_CONCURRENT threads
* running at the same time without returning. When this happens we
* believe you've somehow ended up with a recursive module dependency
* creating a loop.
*
* We have no option but to fail.
*
* Userspace should proactively try to detect and prevent these.
*/
#define MAX_KMOD_ALL_BUSY_TIMEOUT 5
/*
modprobe_path is set via /proc/sys.
*/
modules: add CONFIG_MODPROBE_PATH Allow the developer to specifiy the initial value of the modprobe_path[] string. This can be used to set it to the empty string initially, thus effectively disabling request_module() during early boot until userspace writes a new value via the /proc/sys/kernel/modprobe interface. [1] When building a custom kernel (often for an embedded target), it's normal to build everything into the kernel that is needed for booting, and indeed the initramfs often contains no modules at all, so every such request_module() done before userspace init has mounted the real rootfs is a waste of time. This is particularly useful when combined with the previous patch, which made the initramfs unpacking asynchronous - for that to work, it had to make any usermodehelper call wait for the unpacking to finish before attempting to invoke the userspace helper. By eliminating all such (known-to-be-futile) calls of usermodehelper, the initramfs unpacking and the {device,late}_initcalls can proceed in parallel for much longer. For a relatively slow ppc board I'm working on, the two patches combined lead to 0.2s faster boot - but more importantly, the fact that the initramfs unpacking proceeds completely in the background while devices get probed means I get to handle the gpio watchdog in time without getting reset. [1] __request_module() already has an early -ENOENT return when modprobe_path is the empty string. Link: https://lkml.kernel.org/r/20210313212528.2956377-3-linux@rasmusvillemoes.dk Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Jessica Yu <jeyu@kernel.org> Acked-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Takashi Iwai <tiwai@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-05-07 01:05:45 +00:00
char modprobe_path[KMOD_PATH_LEN] = CONFIG_MODPROBE_PATH;
static void free_modprobe_argv(struct subprocess_info *info)
{
kfree(info->argv[3]); /* check call_modprobe() */
kfree(info->argv);
}
static int call_modprobe(char *module_name, int wait)
{
struct subprocess_info *info;
static char *envp[] = {
"HOME=/",
"TERM=linux",
"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
NULL
};
char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
if (!argv)
goto out;
module_name = kstrdup(module_name, GFP_KERNEL);
if (!module_name)
goto free_argv;
argv[0] = modprobe_path;
argv[1] = "-q";
argv[2] = "--";
argv[3] = module_name; /* check free_modprobe_argv() */
argv[4] = NULL;
info = call_usermodehelper_setup(modprobe_path, argv, envp, GFP_KERNEL,
NULL, free_modprobe_argv, NULL);
if (!info)
goto free_module_name;
return call_usermodehelper_exec(info, wait | UMH_KILLABLE);
free_module_name:
kfree(module_name);
free_argv:
kfree(argv);
out:
return -ENOMEM;
}
/**
* __request_module - try to load a kernel module
* @wait: wait (or not) for the operation to complete
* @fmt: printf style format string for the name of the module
* @...: arguments as specified in the format string
*
* Load a module using the user mode module loader. The function returns
* zero on success or a negative errno code or positive exit code from
* "modprobe" on failure. Note that a successful module load does not mean
* the module did not then unload and exit on an error of its own. Callers
* must check that the service they requested is now available not blindly
* invoke it.
*
* If module auto-loading support is disabled then this function
kmod: make request_module() return an error when autoloading is disabled Patch series "module autoloading fixes and cleanups", v5. This series fixes a bug where request_module() was reporting success to kernel code when module autoloading had been completely disabled via 'echo > /proc/sys/kernel/modprobe'. It also addresses the issues raised on the original thread (https://lkml.kernel.org/lkml/20200310223731.126894-1-ebiggers@kernel.org/T/#u) bydocumenting the modprobe sysctl, adding a self-test for the empty path case, and downgrading a user-reachable WARN_ONCE(). This patch (of 4): It's long been possible to disable kernel module autoloading completely (while still allowing manual module insertion) by setting /proc/sys/kernel/modprobe to the empty string. This can be preferable to setting it to a nonexistent file since it avoids the overhead of an attempted execve(), avoids potential deadlocks, and avoids the call to security_kernel_module_request() and thus on SELinux-based systems eliminates the need to write SELinux rules to dontaudit module_request. However, when module autoloading is disabled in this way, request_module() returns 0. This is broken because callers expect 0 to mean that the module was successfully loaded. Apparently this was never noticed because this method of disabling module autoloading isn't used much, and also most callers don't use the return value of request_module() since it's always necessary to check whether the module registered its functionality or not anyway. But improperly returning 0 can indeed confuse a few callers, for example get_fs_type() in fs/filesystems.c where it causes a WARNING to be hit: if (!fs && (request_module("fs-%.*s", len, name) == 0)) { fs = __get_fs_type(name, len); WARN_ONCE(!fs, "request_module fs-%.*s succeeded, but still no fs?\n", len, name); } This is easily reproduced with: echo > /proc/sys/kernel/modprobe mount -t NONEXISTENT none / It causes: request_module fs-NONEXISTENT succeeded, but still no fs? WARNING: CPU: 1 PID: 1106 at fs/filesystems.c:275 get_fs_type+0xd6/0xf0 [...] This should actually use pr_warn_once() rather than WARN_ONCE(), since it's also user-reachable if userspace immediately unloads the module. Regardless, request_module() should correctly return an error when it fails. So let's make it return -ENOENT, which matches the error when the modprobe binary doesn't exist. I've also sent patches to document and test this case. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Jessica Yu <jeyu@kernel.org> Acked-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jeff Vander Stoep <jeffv@google.com> Cc: Ben Hutchings <benh@debian.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/20200310223731.126894-1-ebiggers@kernel.org Link: http://lkml.kernel.org/r/20200312202552.241885-1-ebiggers@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-10 21:33:43 +00:00
* simply returns -ENOENT.
*/
int __request_module(bool wait, const char *fmt, ...)
{
va_list args;
char module_name[MODULE_NAME_LEN];
int ret;
/*
* We don't allow synchronous module loading from async. Module
* init may invoke async_synchronize_full() which will end up
* waiting for this task which already is waiting for the module
* loading to complete, leading to a deadlock.
*/
WARN_ON_ONCE(wait && current_is_async());
if (!modprobe_path[0])
kmod: make request_module() return an error when autoloading is disabled Patch series "module autoloading fixes and cleanups", v5. This series fixes a bug where request_module() was reporting success to kernel code when module autoloading had been completely disabled via 'echo > /proc/sys/kernel/modprobe'. It also addresses the issues raised on the original thread (https://lkml.kernel.org/lkml/20200310223731.126894-1-ebiggers@kernel.org/T/#u) bydocumenting the modprobe sysctl, adding a self-test for the empty path case, and downgrading a user-reachable WARN_ONCE(). This patch (of 4): It's long been possible to disable kernel module autoloading completely (while still allowing manual module insertion) by setting /proc/sys/kernel/modprobe to the empty string. This can be preferable to setting it to a nonexistent file since it avoids the overhead of an attempted execve(), avoids potential deadlocks, and avoids the call to security_kernel_module_request() and thus on SELinux-based systems eliminates the need to write SELinux rules to dontaudit module_request. However, when module autoloading is disabled in this way, request_module() returns 0. This is broken because callers expect 0 to mean that the module was successfully loaded. Apparently this was never noticed because this method of disabling module autoloading isn't used much, and also most callers don't use the return value of request_module() since it's always necessary to check whether the module registered its functionality or not anyway. But improperly returning 0 can indeed confuse a few callers, for example get_fs_type() in fs/filesystems.c where it causes a WARNING to be hit: if (!fs && (request_module("fs-%.*s", len, name) == 0)) { fs = __get_fs_type(name, len); WARN_ONCE(!fs, "request_module fs-%.*s succeeded, but still no fs?\n", len, name); } This is easily reproduced with: echo > /proc/sys/kernel/modprobe mount -t NONEXISTENT none / It causes: request_module fs-NONEXISTENT succeeded, but still no fs? WARNING: CPU: 1 PID: 1106 at fs/filesystems.c:275 get_fs_type+0xd6/0xf0 [...] This should actually use pr_warn_once() rather than WARN_ONCE(), since it's also user-reachable if userspace immediately unloads the module. Regardless, request_module() should correctly return an error when it fails. So let's make it return -ENOENT, which matches the error when the modprobe binary doesn't exist. I've also sent patches to document and test this case. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Jessica Yu <jeyu@kernel.org> Acked-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jeff Vander Stoep <jeffv@google.com> Cc: Ben Hutchings <benh@debian.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/20200310223731.126894-1-ebiggers@kernel.org Link: http://lkml.kernel.org/r/20200312202552.241885-1-ebiggers@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-10 21:33:43 +00:00
return -ENOENT;
va_start(args, fmt);
ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
va_end(args);
if (ret >= MODULE_NAME_LEN)
return -ENAMETOOLONG;
ret = security_kernel_module_request(module_name);
if (ret)
return ret;
kmod: reduce atomic operations on kmod_concurrent and simplify When checking if we want to allow a kmod thread to kick off we increment, then read to see if we should enable a thread. If we were over the allowed limit limit we decrement. Splitting the increment far apart from decrement means there could be a time where two increments happen potentially giving a false failure on a thread which should have been allowed. CPU1 CPU2 atomic_inc() atomic_inc() atomic_read() atomic_read() atomic_dec() atomic_dec() In this case a read on CPU1 gets the atomic_inc()'s and we could negate it from getting a kmod thread. We could try to prevent this with a lock or preemption but that is overkill. We can fix by reducing the number of atomic operations. We do this by inverting the logic of of the enabler, instead of incrementing kmod_concurrent as we get new kmod users, define the variable kmod_concurrent_max as the max number of currently allowed kmod users and as we get new kmod users just decrement it if its still positive. This combines the dec and read in one atomic operation. In this case we no longer get the same false failure: CPU1 CPU2 atomic_dec_if_positive() atomic_dec_if_positive() atomic_inc() atomic_inc() The number of threads is computed at init, and since the current computation of kmod_concurrent includes the thread count we can avoid setting kmod_concurrent_max later in boot through an init call by simply sticking to 50 as the kmod_concurrent_max. The assumption here is a system with modules must at least have ~16 MiB of RAM. Suggested-by: Petr Mladek <pmladek@suse.com> Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
2017-06-23 19:19:12 +00:00
if (atomic_dec_if_positive(&kmod_concurrent_max) < 0) {
kmod: throttle kmod thread limit If we reach the limit of modprobe_limit threads running the next request_module() call will fail. The original reason for adding a kill was to do away with possible issues with in old circumstances which would create a recursive series of request_module() calls. We can do better than just be super aggressive and reject calls once we've reached the limit by simply making pending callers wait until the threshold has been reduced, and then throttling them in, one by one. This throttling enables requests over the kmod concurrent limit to be processed once a pending request completes. Only the first item queued up to wait is woken up. The assumption here is once a task is woken it will have no other option to also kick the queue to check if there are more pending tasks -- regardless of whether or not it was successful. By throttling and processing only max kmod concurrent tasks we ensure we avoid unexpected fatal request_module() calls, and we keep memory consumption on module loading to a minimum. With x86_64 qemu, with 4 cores, 4 GiB of RAM it takes the following run time to run both tests: time ./kmod.sh -t 0008 real 0m16.366s user 0m0.883s sys 0m8.916s time ./kmod.sh -t 0009 real 0m50.803s user 0m0.791s sys 0m9.852s Link: http://lkml.kernel.org/r/20170628223155.26472-4-mcgrof@kernel.org Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Cc: Jessica Yu <jeyu@redhat.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Michal Marek <mmarek@suse.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-14 21:50:11 +00:00
pr_warn_ratelimited("request_module: kmod_concurrent_max (%u) close to 0 (max_modprobes: %u), for module %s, throttling...",
atomic_read(&kmod_concurrent_max),
MAX_KMOD_CONCURRENT, module_name);
kmod: fix wait on recursive loop Recursive loops with module loading were previously handled in kmod by restricting the number of modprobe calls to 50 and if that limit was breached request_module() would return an error and a user would see the following on their kernel dmesg: request_module: runaway loop modprobe binfmt-464c Starting init:/sbin/init exists but couldn't execute it (error -8) This issue could happen for instance when a 64-bit kernel boots a 32-bit userspace on some architectures and has no 32-bit binary format hanlders. This is visible, for instance, when a CONFIG_MODULES enabled 64-bit MIPS kernel boots a into o32 root filesystem and the binfmt handler for o32 binaries is not built-in. After commit 6d7964a722af ("kmod: throttle kmod thread limit") we now don't have any visible signs of an error and the kernel just waits for the loop to end somehow. Although this *particular* recursive loop could also be addressed by doing a sanity check on search_binary_handler() and disallowing a modular binfmt to be required for modprobe, a generic solution for any recursive kernel kmod issues is still needed. This should catch these loops. We can investigate each loop and address each one separately as they come in, this however puts a stop gap for them as before. Link: http://lkml.kernel.org/r/20170809234635.13443-3-mcgrof@kernel.org Fixes: 6d7964a722af ("kmod: throttle kmod thread limit") Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reported-by: Matt Redfearn <matt.redfearn@imgtec.com> Tested-by: Matt Redfearn <matt.redfearn@imgetc.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Colin Ian King <colin.king@canonical.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Daniel Mentz <danielmentz@google.com> Cc: David Binderman <dcb314@hotmail.com> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jessica Yu <jeyu@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Michal Marek <mmarek@suse.com> Cc: Miroslav Benes <mbenes@suse.cz> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-08-18 22:15:58 +00:00
ret = wait_event_killable_timeout(kmod_wq,
atomic_dec_if_positive(&kmod_concurrent_max) >= 0,
MAX_KMOD_ALL_BUSY_TIMEOUT * HZ);
if (!ret) {
pr_warn_ratelimited("request_module: modprobe %s cannot be processed, kmod busy with %d threads for more than %d seconds now",
module_name, MAX_KMOD_CONCURRENT, MAX_KMOD_ALL_BUSY_TIMEOUT);
return -ETIME;
} else if (ret == -ERESTARTSYS) {
pr_warn_ratelimited("request_module: sigkill sent for modprobe %s, giving up", module_name);
return ret;
}
}
tracing/events: Add module tracepoints Add trace points to trace module_load, module_free, module_get, module_put and module_request, and use trace_event facility to get the trace output. Here's the sample output: TASK-PID CPU# TIMESTAMP FUNCTION | | | | | <...>-42 [000] 1.758380: module_request: fb0 wait=1 call_site=fb_open ... <...>-60 [000] 3.269403: module_load: scsi_wait_scan <...>-60 [000] 3.269432: module_put: scsi_wait_scan call_site=sys_init_module refcnt=0 <...>-61 [001] 3.273168: module_free: scsi_wait_scan ... <...>-1021 [000] 13.836081: module_load: sunrpc <...>-1021 [000] 13.840589: module_put: sunrpc call_site=sys_init_module refcnt=-1 <...>-1027 [000] 13.848098: module_get: sunrpc call_site=try_module_get refcnt=0 <...>-1027 [000] 13.848308: module_get: sunrpc call_site=get_filesystem refcnt=1 <...>-1027 [000] 13.848692: module_put: sunrpc call_site=put_filesystem refcnt=0 ... modprobe-2587 [001] 1088.437213: module_load: trace_events_sample F modprobe-2587 [001] 1088.437786: module_put: trace_events_sample call_site=sys_init_module refcnt=0 Note: - the taints flag can be 'F', 'C' and/or 'P' if mod->taints != 0 - the module refcnt is percpu, so it can be negative in a specific cpu Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Rusty Russell <rusty@rustcorp.com.au> LKML-Reference: <4A891B3C.5030608@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-08-17 08:56:28 +00:00
trace_module_request(module_name, wait, _RET_IP_);
ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
kmod: add init function to usermodehelper About 6 months ago, I made a set of changes to how the core-dump-to-a-pipe feature in the kernel works. We had reports of several races, including some reports of apps bypassing our recursion check so that a process that was forked as part of a core_pattern setup could infinitely crash and refork until the system crashed. We fixed those by improving our recursion checks. The new check basically refuses to fork a process if its core limit is zero, which works well. Unfortunately, I've been getting grief from maintainer of user space programs that are inserted as the forked process of core_pattern. They contend that in order for their programs (such as abrt and apport) to work, all the running processes in a system must have their core limits set to a non-zero value, to which I say 'yes'. I did this by design, and think thats the right way to do things. But I've been asked to ease this burden on user space enough times that I thought I would take a look at it. The first suggestion was to make the recursion check fail on a non-zero 'special' number, like one. That way the core collector process could set its core size ulimit to 1, and enable the kernel's recursion detection. This isn't a bad idea on the surface, but I don't like it since its opt-in, in that if a program like abrt or apport has a bug and fails to set such a core limit, we're left with a recursively crashing system again. So I've come up with this. What I've done is modify the call_usermodehelper api such that an extra parameter is added, a function pointer which will be called by the user helper task, after it forks, but before it exec's the required process. This will give the caller the opportunity to get a call back in the processes context, allowing it to do whatever it needs to to the process in the kernel prior to exec-ing the user space code. In the case of do_coredump, this callback is ues to set the core ulimit of the helper process to 1. This elimnates the opt-in problem that I had above, as it allows the ulimit for core sizes to be set to the value of 1, which is what the recursion check looks for in do_coredump. This patch: Create new function call_usermodehelper_fns() and allow it to assign both an init and cleanup function, as we'll as arbitrary data. The init function is called from the context of the forked process and allows for customization of the helper process prior to calling exec. Its return code gates the continuation of the process, or causes its exit. Also add an arbitrary data pointer to the subprocess_info struct allowing for data to be passed from the caller to the new process, and the subsequent cleanup process Also, use this patch to cleanup the cleanup function. It currently takes an argp and envp pointer for freeing, which is ugly. Lets instead just make the subprocess_info structure public, and pass that to the cleanup and init routines Signed-off-by: Neil Horman <nhorman@tuxdriver.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-26 21:42:58 +00:00
kmod: reduce atomic operations on kmod_concurrent and simplify When checking if we want to allow a kmod thread to kick off we increment, then read to see if we should enable a thread. If we were over the allowed limit limit we decrement. Splitting the increment far apart from decrement means there could be a time where two increments happen potentially giving a false failure on a thread which should have been allowed. CPU1 CPU2 atomic_inc() atomic_inc() atomic_read() atomic_read() atomic_dec() atomic_dec() In this case a read on CPU1 gets the atomic_inc()'s and we could negate it from getting a kmod thread. We could try to prevent this with a lock or preemption but that is overkill. We can fix by reducing the number of atomic operations. We do this by inverting the logic of of the enabler, instead of incrementing kmod_concurrent as we get new kmod users, define the variable kmod_concurrent_max as the max number of currently allowed kmod users and as we get new kmod users just decrement it if its still positive. This combines the dec and read in one atomic operation. In this case we no longer get the same false failure: CPU1 CPU2 atomic_dec_if_positive() atomic_dec_if_positive() atomic_inc() atomic_inc() The number of threads is computed at init, and since the current computation of kmod_concurrent includes the thread count we can avoid setting kmod_concurrent_max later in boot through an init call by simply sticking to 50 as the kmod_concurrent_max. The assumption here is a system with modules must at least have ~16 MiB of RAM. Suggested-by: Petr Mladek <pmladek@suse.com> Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
2017-06-23 19:19:12 +00:00
atomic_inc(&kmod_concurrent_max);
kmod: throttle kmod thread limit If we reach the limit of modprobe_limit threads running the next request_module() call will fail. The original reason for adding a kill was to do away with possible issues with in old circumstances which would create a recursive series of request_module() calls. We can do better than just be super aggressive and reject calls once we've reached the limit by simply making pending callers wait until the threshold has been reduced, and then throttling them in, one by one. This throttling enables requests over the kmod concurrent limit to be processed once a pending request completes. Only the first item queued up to wait is woken up. The assumption here is once a task is woken it will have no other option to also kick the queue to check if there are more pending tasks -- regardless of whether or not it was successful. By throttling and processing only max kmod concurrent tasks we ensure we avoid unexpected fatal request_module() calls, and we keep memory consumption on module loading to a minimum. With x86_64 qemu, with 4 cores, 4 GiB of RAM it takes the following run time to run both tests: time ./kmod.sh -t 0008 real 0m16.366s user 0m0.883s sys 0m8.916s time ./kmod.sh -t 0009 real 0m50.803s user 0m0.791s sys 0m9.852s Link: http://lkml.kernel.org/r/20170628223155.26472-4-mcgrof@kernel.org Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Cc: Jessica Yu <jeyu@redhat.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Michal Marek <mmarek@suse.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-14 21:50:11 +00:00
wake_up(&kmod_wq);
kmod: reduce atomic operations on kmod_concurrent and simplify When checking if we want to allow a kmod thread to kick off we increment, then read to see if we should enable a thread. If we were over the allowed limit limit we decrement. Splitting the increment far apart from decrement means there could be a time where two increments happen potentially giving a false failure on a thread which should have been allowed. CPU1 CPU2 atomic_inc() atomic_inc() atomic_read() atomic_read() atomic_dec() atomic_dec() In this case a read on CPU1 gets the atomic_inc()'s and we could negate it from getting a kmod thread. We could try to prevent this with a lock or preemption but that is overkill. We can fix by reducing the number of atomic operations. We do this by inverting the logic of of the enabler, instead of incrementing kmod_concurrent as we get new kmod users, define the variable kmod_concurrent_max as the max number of currently allowed kmod users and as we get new kmod users just decrement it if its still positive. This combines the dec and read in one atomic operation. In this case we no longer get the same false failure: CPU1 CPU2 atomic_dec_if_positive() atomic_dec_if_positive() atomic_inc() atomic_inc() The number of threads is computed at init, and since the current computation of kmod_concurrent includes the thread count we can avoid setting kmod_concurrent_max later in boot through an init call by simply sticking to 50 as the kmod_concurrent_max. The assumption here is a system with modules must at least have ~16 MiB of RAM. Suggested-by: Petr Mladek <pmladek@suse.com> Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
2017-06-23 19:19:12 +00:00
return ret;
}
EXPORT_SYMBOL(__request_module);