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Fedor Pchelkin 71eeddcad7 autofs: fix memory leak of waitqueues in autofs_catatonic_mode 
[ Upstream commit ccbe77f7e4 ]

Syzkaller reports a memory leak:

BUG: memory leak
unreferenced object 0xffff88810b279e00 (size 96):
  comm "syz-executor399", pid 3631, jiffies 4294964921 (age 23.870s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 08 9e 27 0b 81 88 ff ff  ..........'.....
    08 9e 27 0b 81 88 ff ff 00 00 00 00 00 00 00 00  ..'.............
  backtrace:
    [<ffffffff814cfc90>] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046
    [<ffffffff81bb75ca>] kmalloc include/linux/slab.h:576 [inline]
    [<ffffffff81bb75ca>] autofs_wait+0x3fa/0x9a0 fs/autofs/waitq.c:378
    [<ffffffff81bb88a7>] autofs_do_expire_multi+0xa7/0x3e0 fs/autofs/expire.c:593
    [<ffffffff81bb8c33>] autofs_expire_multi+0x53/0x80 fs/autofs/expire.c:619
    [<ffffffff81bb6972>] autofs_root_ioctl_unlocked+0x322/0x3b0 fs/autofs/root.c:897
    [<ffffffff81bb6a95>] autofs_root_ioctl+0x25/0x30 fs/autofs/root.c:910
    [<ffffffff81602a9c>] vfs_ioctl fs/ioctl.c:51 [inline]
    [<ffffffff81602a9c>] __do_sys_ioctl fs/ioctl.c:870 [inline]
    [<ffffffff81602a9c>] __se_sys_ioctl fs/ioctl.c:856 [inline]
    [<ffffffff81602a9c>] __x64_sys_ioctl+0xfc/0x140 fs/ioctl.c:856
    [<ffffffff84608225>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    [<ffffffff84608225>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    [<ffffffff84800087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

autofs_wait_queue structs should be freed if their wait_ctr becomes zero.
Otherwise they will be lost.

In this case an AUTOFS_IOC_EXPIRE_MULTI ioctl is done, then a new
waitqueue struct is allocated in autofs_wait(), its initial wait_ctr
equals 2. After that wait_event_killable() is interrupted (it returns
-ERESTARTSYS), so that 'wq->name.name == NULL' condition may be not
satisfied. Actually, this condition can be satisfied when
autofs_wait_release() or autofs_catatonic_mode() is called and, what is
also important, wait_ctr is decremented in those places. Upon the exit of
autofs_wait(), wait_ctr is decremented to 1. Then the unmounting process
begins: kill_sb calls autofs_catatonic_mode(), which should have freed the
waitqueues, but it only decrements its usage counter to zero which is not
a correct behaviour.

edit:imk
This description is of course not correct. The umount performed as a result
of an expire is a umount of a mount that has been automounted, it's not the
autofs mount itself. They happen independently, usually after everything
mounted within the autofs file system has been expired away. If everything
hasn't been expired away the automount daemon can still exit leaving mounts
in place. But expires done in both cases will result in a notification that
calls autofs_wait_release() with a result status. The problem case is the
summary execution of of the automount daemon. In this case any waiting
processes won't be woken up until either they are terminated or the mount
is umounted.
end edit: imk

So in catatonic mode we should free waitqueues which counter becomes zero.

edit: imk
Initially I was concerned that the calling of autofs_wait_release() and
autofs_catatonic_mode() was not mutually exclusive but that can't be the
case (obviously) because the queue entry (or entries) is removed from the
list when either of these two functions are called. Consequently the wait
entry will be freed by only one of these functions or by the woken process
in autofs_wait() depending on the order of the calls.
end edit: imk

Reported-by: syzbot+5e53f70e69ff0c0a1c0c@syzkaller.appspotmail.com
Suggested-by: Takeshi Misawa <jeliantsurux@gmail.com>
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: autofs@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Message-Id: <169112719161.7590.6700123246297365841.stgit@donald.themaw.net>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-09-23 11:09:54 +02:00
arch MIPS: Only fiddle with CHECKFLAGS if `need-compiler' 2023-09-19 12:23:04 +02:00
block block: don't add or resize partition on the disk with GENHD_FL_NO_PART 2023-09-19 12:23:03 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto X.509: if signature is unsupported skip validation 2023-09-19 12:22:52 +02:00
Documentation dt-bindings: clock: xlnx,versal-clk: drop select:false 2023-09-19 12:22:56 +02:00
drivers pcd: fix error codes in pcd_init_unit() 2023-09-19 12:23:04 +02:00
fs
include ipv6: fix ip6_sock_set_addr_preferences() typo 2023-09-19 12:23:04 +02:00
init x86/mm: Initialize text poking earlier 2023-08-08 19:58:33 +02:00
io_uring io_uring: break iopolling on signal 2023-09-19 12:22:54 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY 2023-09-19 12:22:53 +02:00
lib lib: test_scanf: Add explicit type cast to result initialization in test_number_prefix() 2023-09-19 12:23:01 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/vmalloc: add a safer version of find_vm_area() for debug 2023-09-19 12:22:50 +02:00
net kcm: Fix error handling for SOCK_DGRAM in kcm_sendmsg(). 2023-09-19 12:23:04 +02:00
samples samples/bpf: fix broken map lookup probe 2023-09-19 12:22:34 +02:00
scripts kconfig: fix possible buffer overflow 2023-09-19 12:22:56 +02:00
security smackfs: Prevent underflow in smk_set_cipso() 2023-09-19 12:22:39 +02:00
sound ALSA: pcm: Fix missing fixup call in compat hw_refine ioctl 2023-09-19 12:22:50 +02:00
tools kselftest/runner.sh: Propagate SIGTERM to runner child 2023-09-19 12:23:03 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:22:40 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS iio: stx104: Move to addac subdirectory 2023-08-26 14:23:27 +02:00
Makefile Linux 5.15.132 2023-09-19 12:23:04 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.