[moderation] [block?] [trace?] KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 243f750a2df0 Merge tag 'gpio-fixes-for-v6.13-rc3' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=147324f8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1fe4854f351e948c
dashboard link: https://syzkaller.appspot.com/bug?extid=33cd3ee18319284d41c7
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org linux-tra...@vger.kernel.org mathieu....@efficios.com mhir...@kernel.org ros...@goodmis.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2125b9ae9a18/disk-243f750a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7227f9bc5863/vmlinux-243f750a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/85211c812635/bzImage-243f750a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+33cd3e...@syzkaller.appspotmail.com

loop5: detected capacity change from 0 to 8192
==================================================================
BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888103504238 of 8 bytes by task 3291 on cpu 0:
relay_switch_subbuf+0x39e/0x3b0 kernel/relay.c:708
relay_reserve include/linux/relay.h:248 [inline]
__blk_add_trace+0x66a/0x730 kernel/trace/blktrace.c:276
blk_add_trace_plug+0x4c/0x70 kernel/trace/blktrace.c:949
trace_block_plug include/trace/events/block.h:430 [inline]
blk_add_rq_to_plug+0x31b/0x3d0 block/blk-mq.c:1378
blk_mq_submit_bio+0x96c/0xe40 block/blk-mq.c:3148
__submit_bio+0xf2/0x470 block/blk-core.c:629
__submit_bio_noacct_mq block/blk-core.c:710 [inline]
submit_bio_noacct_nocheck+0x295/0x6e0 block/blk-core.c:739
submit_bio_noacct+0x766/0x9a0 block/blk-core.c:868
submit_bio+0x218/0x230 block/blk-core.c:910
submit_bh_wbc+0x2ed/0x330 fs/buffer.c:2814
submit_bh fs/buffer.c:2819 [inline]
block_read_full_folio+0x663/0x6f0 fs/buffer.c:2446
blkdev_read_folio+0x1c/0x30 block/fops.c:442
filemap_read_folio mm/filemap.c:2366 [inline]
filemap_update_page mm/filemap.c:2450 [inline]
filemap_get_pages+0xddc/0x10e0 mm/filemap.c:2571
filemap_read+0x221/0x6a0 mm/filemap.c:2646
blkdev_read_iter+0x20e/0x2c0 block/fops.c:770
new_sync_read fs/read_write.c:484 [inline]
vfs_read+0x5dc/0x700 fs/read_write.c:565
ksys_read+0xe8/0x1b0 fs/read_write.c:708
__do_sys_read fs/read_write.c:717 [inline]
__se_sys_read fs/read_write.c:715 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:715
x64_sys_call+0x2874/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888103504238 of 8 bytes by task 7022 on cpu 1:
relay_switch_subbuf+0x39e/0x3b0 kernel/relay.c:708
relay_reserve include/linux/relay.h:248 [inline]
__blk_add_trace+0x66a/0x730 kernel/trace/blktrace.c:276
blk_add_trace_unplug+0x76/0xb0 kernel/trace/blktrace.c:969
trace_block_unplug include/trace/events/block.h:475 [inline]
blk_mq_flush_plug_list+0xe9c/0xef0 block/blk-mq.c:2893
__blk_flush_plug+0x216/0x290 block/blk-core.c:1213
blk_finish_plug block/blk-core.c:1240 [inline]
__submit_bio+0x280/0x470 block/blk-core.c:637
__submit_bio_noacct_mq block/blk-core.c:710 [inline]
submit_bio_noacct_nocheck+0x295/0x6e0 block/blk-core.c:739
submit_bio_noacct+0x766/0x9a0 block/blk-core.c:868
submit_bio+0x218/0x230 block/blk-core.c:910
submit_bh_wbc+0x2ed/0x330 fs/buffer.c:2814
submit_bh fs/buffer.c:2819 [inline]
__bread_slow fs/buffer.c:1264 [inline]
__bread_gfp+0x17c/0x280 fs/buffer.c:1488
sb_bread include/linux/buffer_head.h:346 [inline]
fat__get_entry fs/fat/dir.c:100 [inline]
fat_get_entry+0x482/0x5f0 fs/fat/dir.c:128
fat_get_short_entry fs/fat/dir.c:885 [inline]
fat_subdirs+0xfa/0x190 fs/fat/dir.c:951
fat_read_root+0x31d/0x360 fs/fat/inode.c:1345
fat_fill_super+0x14f5/0x1bf0 fs/fat/inode.c:1814
vfat_fill_super+0x24/0x30 fs/fat/namei_vfat.c:1200
get_tree_bdev_flags+0x29f/0x310 fs/super.c:1636
get_tree_bdev+0x1f/0x30 fs/super.c:1659
vfat_get_tree+0x1c/0x30 fs/fat/namei_vfat.c:1205
vfs_get_tree+0x56/0x1e0 fs/super.c:1814
do_new_mount+0x227/0x690 fs/namespace.c:3507
path_mount+0x49b/0xb30 fs/namespace.c:3834
do_mount fs/namespace.c:3847 [inline]
__do_sys_mount fs/namespace.c:4057 [inline]
__se_sys_mount+0x27c/0x2d0 fs/namespace.c:4034
__x64_sys_mount+0x67/0x80 fs/namespace.c:4034
x64_sys_call+0x2c84/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000030 -> 0x0000000000000038

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7022 Comm: syz.5.985 Not tainted 6.13.0-rc2-syzkaller-00192-g243f750a2df0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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