KCSAN: data-race in __io_import_iovec / io_cqring_overflow_flush

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4429f14a Merge tag 'block-5.10-2020-11-07' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15c02094500000
kernel config: https://syzkaller.appspot.com/x/.config?x=76dfc991796328d4
dashboard link: https://syzkaller.appspot.com/bug?extid=30e9d1352fd743af8606
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ax...@kernel.dk io-u...@vger.kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+30e9d1...@syzkaller.appspotmail.com

EXT4-fs error (device loop5): ext4_empty_dir:2879: inode #12: comm syz-executor.5: Directory hole found for htree leaf block
EXT4-fs error (device loop5): ext4_free_inode:351: comm syz-executor.5: bit already cleared for inode 12
==================================================================
BUG: KCSAN: data-race in __io_import_iovec / io_cqring_overflow_flush

read-write to 0xffff88801c181c44 of 1 bytes by task 663 on cpu 1:
io_cqring_overflow_flush+0x90/0x7f0 fs/io_uring.c:1645
io_uring_cancel_task_requests fs/io_uring.c:8644 [inline]
__io_uring_files_cancel+0x21a/0xff0 fs/io_uring.c:8742
io_uring_files_cancel include/linux/io_uring.h:51 [inline]
exit_files+0x6a/0xc0 fs/file.c:456
do_exit+0x422/0x15a0 kernel/exit.c:801
do_group_exit+0xc8/0x170 kernel/exit.c:903
get_signal+0xf9b/0x1510 kernel/signal.c:2758
arch_do_signal+0x25/0x260 arch/x86/kernel/signal.c:811
exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
exit_to_user_mode_prepare+0xde/0x170 kernel/entry/common.c:191
syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88801c181c44 of 1 bytes by task 633 on cpu 0:
__io_import_iovec+0x26c/0x930 fs/io_uring.c:3111
io_rw_prep_async fs/io_uring.c:3249 [inline]
io_write_prep fs/io_uring.c:3500 [inline]
io_req_prep+0xbad/0x21f0 fs/io_uring.c:5709
io_req_defer_prep fs/io_uring.c:5776 [inline]
io_submit_sqe+0x24d/0x620 fs/io_uring.c:6324
io_submit_sqes+0x99a/0x11a0 fs/io_uring.c:6581
__do_sys_io_uring_enter fs/io_uring.c:8958 [inline]
__se_sys_io_uring_enter+0x52c/0xac0 fs/io_uring.c:8907
__x64_sys_io_uring_enter+0x74/0x80 fs/io_uring.c:8907
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 633 Comm: syz-executor.5 Not tainted 5.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.