[syzbot] [fs?] KCSAN: data-race in inotify_handle_inode_event / inotify_remove_from_idr

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 622322f53c6d Merge tag 'mips-fixes_6.3_2' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1482ffafc80000
kernel config: https://syzkaller.appspot.com/x/.config?x=fa4baf7c6b35b5d5
dashboard link: https://syzkaller.appspot.com/bug?extid=4a06d4373fd52f0b2f9c
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8b5f31d96315/disk-622322f5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/adca7dc8daae/vmlinux-622322f5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ed78ddc31ccb/bzImage-622322f5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4a06d4...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in inotify_handle_inode_event / inotify_remove_from_idr

write to 0xffff888104e31368 of 4 bytes by task 3229 on cpu 1:
inotify_remove_from_idr+0x106/0x310 fs/notify/inotify/inotify_user.c:511
inotify_ignored_and_remove_idr+0x34/0x60 fs/notify/inotify/inotify_user.c:532
inotify_freeing_mark+0x1d/0x30 fs/notify/inotify/inotify_fsnotify.c:133
fsnotify_free_mark fs/notify/mark.c:490 [inline]
fsnotify_destroy_mark+0x17a/0x190 fs/notify/mark.c:499
__do_sys_inotify_rm_watch fs/notify/inotify/inotify_user.c:817 [inline]
__se_sys_inotify_rm_watch+0xf7/0x170 fs/notify/inotify/inotify_user.c:794
__x64_sys_inotify_rm_watch+0x31/0x40 fs/notify/inotify/inotify_user.c:794
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888104e31368 of 4 bytes by task 3638 on cpu 0:
inotify_handle_inode_event+0x17e/0x2c0 fs/notify/inotify/inotify_fsnotify.c:113
fsnotify_handle_inode_event+0x19b/0x1f0 fs/notify/fsnotify.c:264
fsnotify_handle_event fs/notify/fsnotify.c:316 [inline]
send_to_group fs/notify/fsnotify.c:364 [inline]
fsnotify+0x101c/0x1150 fs/notify/fsnotify.c:570
__fsnotify_parent+0x307/0x480 fs/notify/fsnotify.c:230
fsnotify_parent include/linux/fsnotify.h:77 [inline]
fsnotify_file include/linux/fsnotify.h:99 [inline]
fsnotify_close include/linux/fsnotify.h:341 [inline]
__fput+0x4b0/0x570 fs/file_table.c:307
____fput+0x15/0x20 fs/file_table.c:349
task_work_run+0x123/0x160 kernel/task_work.c:179
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xd1/0xe0 kernel/entry/common.c:171
exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:297
do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000060 -> 0xffffffff

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3638 Comm: syz-executor.0 Not tainted 6.3.0-rc7-syzkaller-00191-g622322f53c6d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
==================================================================


---
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[Dmitry Vyukov]

On Mon, 24 Apr 2023 at 10:09, syzbot
<syzbot+4a06d4...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 622322f53c6d Merge tag 'mips-fixes_6.3_2' of git://git.ker..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1482ffafc80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=fa4baf7c6b35b5d5
> dashboard link: https://syzkaller.appspot.com/bug?extid=4a06d4373fd52f0b2f9c
> compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/8b5f31d96315/disk-622322f5.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/adca7dc8daae/vmlinux-622322f5.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/ed78ddc31ccb/bzImage-622322f5.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+4a06d4...@syzkaller.appspotmail.com

If I am reading this correctly, userspace can get wd=-1 as the result
of this race. Docs say wd must refer to a previously allocated
descriptor, which is positive. I don't see any mentions of semantics
of wd=-1.

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[Jan Kara]

On Mon 24-04-23 10:27:46, Dmitry Vyukov wrote:
> On Mon, 24 Apr 2023 at 10:09, syzbot
> <syzbot+4a06d4...@syzkaller.appspotmail.com> wrote:
> >
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 622322f53c6d Merge tag 'mips-fixes_6.3_2' of git://git.ker..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1482ffafc80000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=fa4baf7c6b35b5d5
> > dashboard link: https://syzkaller.appspot.com/bug?extid=4a06d4373fd52f0b2f9c
> > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/8b5f31d96315/disk-622322f5.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/adca7dc8daae/vmlinux-622322f5.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/ed78ddc31ccb/bzImage-622322f5.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+4a06d4...@syzkaller.appspotmail.com
>
> If I am reading this correctly, userspace can get wd=-1 as the result
> of this race. Docs say wd must refer to a previously allocated
> descriptor, which is positive. I don't see any mentions of semantics
> of wd=-1.

Yeah, indeed this looks like a possible race when we detach the mark just
while we are generating the event. I'll send a fix.

Honza

--
Jan Kara <ja...@suse.com>
SUSE Labs, CR