KCSAN: data-race in bio_chain / bio_endio

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 05f22368 x86, kcsan: Enable KCSAN for x86
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=151a13b0e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
dashboard link: https://syzkaller.appspot.com/bug?extid=1c03b20daf4bd4db42cf
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [ax...@kernel.dk linux...@vger.kernel.org
linux-...@vger.kernel.org el...@google.com]

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1c03b2...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in bio_chain / bio_endio

read to 0xffff888121e65d94 of 2 bytes by interrupt on cpu 1:
bio_remaining_done block/bio.c:1757 [inline]
bio_endio+0x3e/0x4f0 block/bio.c:1787
req_bio_endio block/blk-core.c:242 [inline]
blk_update_request+0x427/0x7b0 block/blk-core.c:1462
scsi_end_request+0x6b/0x3e0 drivers/scsi/scsi_lib.c:579
scsi_io_completion+0x11d/0xc80 drivers/scsi/scsi_lib.c:963
scsi_finish_command+0x280/0x380 drivers/scsi/scsi.c:228
scsi_softirq_done+0x259/0x280 drivers/scsi/scsi_lib.c:1477
blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
__do_softirq+0x115/0x33f kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0xbb/0xe0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
do_IRQ+0xa6/0x180 arch/x86/kernel/irq.c:263
ret_from_intr+0x0/0x19
arch_local_irq_restore arch/x86/include/asm/paravirt.h:756 [inline]
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
_raw_spin_unlock_irqrestore+0x51/0x80 kernel/locking/spinlock.c:191
spin_unlock_irqrestore include/linux/spinlock.h:393 [inline]
release_pages+0x25a/0xa90 mm/swap.c:839
__pagevec_release+0x53/0x90 mm/swap.c:862

write to 0xffff888121e65d94 of 2 bytes by task 11251 on cpu 0:
bio_set_flag include/linux/bio.h:239 [inline]
bio_inc_remaining include/linux/bio.h:689 [inline]
bio_chain+0x86/0xb0 block/bio.c:333
__blk_queue_split+0x745/0xb40 block/blk-merge.c:330
blk_mq_make_request+0x104/0xf60 block/blk-mq.c:1959
generic_make_request block/blk-core.c:1064 [inline]
generic_make_request+0x196/0x740 block/blk-core.c:1006
submit_bio+0x96/0x3c0 block/blk-core.c:1190
dio_bio_submit fs/direct-io.c:481 [inline]
do_blockdev_direct_IO+0x64e1/0x78c0 fs/direct-io.c:1353
__blockdev_direct_IO+0x86/0xa0 fs/direct-io.c:1412
ext4_direct_IO_write fs/ext4/inode.c:3742 [inline]
ext4_direct_IO+0x6f5/0xf70 fs/ext4/inode.c:3871
generic_file_direct_write+0x14d/0x2e0 mm/filemap.c:3207
__generic_file_write_iter+0x17e/0x380 mm/filemap.c:3390
ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
call_write_iter include/linux/fs.h:1895 [inline]
new_sync_write+0x388/0x4a0 fs/read_write.c:483
__vfs_write+0xb1/0xc0 fs/read_write.c:496

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11251 Comm: syz-executor.0 Not tainted 5.4.0-rc3+ #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.