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Syzbot reports a NULL-ptr deref in the kref_put() call:
BUG: KASAN: null-ptr-deref in media_request_put drivers/media/mc/mc-request.c:81 [inline]
kref_put include/linux/kref.h:64 [inline]
media_request_put drivers/media/mc/mc-request.c:81 [inline]
media_request_close+0x4d/0x170 drivers/media/mc/mc-request.c:89
__fput+0x2ed/0x750 fs/file_table.c:281
task_work_run+0x147/0x1d0 kernel/task_work.c:123
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop arch/x86/entry/common.c:165 [inline]
prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:196
What led to this crash was an injected memory allocation failure in
media_request_alloc():
FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
should_failslab+0x5/0x20
kmem_cache_alloc_trace+0x57/0x300
? anon_inode_getfile+0xe5/0x170
media_request_alloc+0x339/0x440
media_device_request_alloc+0x94/0xc0
media_device_ioctl+0x1fb/0x330
? do_vfs_ioctl+0x6ea/0x1a00
? media_ioctl+0x101/0x120
? __media_device_usb_init+0x430/0x430
? media_poll+0x110/0x110
__se_sys_ioctl+0xf9/0x160
do_syscall_64+0xf3/0x1b0
When that allocation fails, filp->private_data is left uninitialized
which media_request_close() does not expect and crashes.
To avoid this, reorder media_request_alloc() such that
allocating the struct file happens as the last step thus
media_request_close() will no longer get called for a partially created
media request.
Reported-by: syzbot+6bed2d543cf7e48b822b@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Fixes: 10905d70d7 ("media: media-request: implement media requests")
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
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.