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BUG: KCSAN: data-race in __mod_timer / blk_add_timer

write to 0xffff888102545e08 of 8 bytes by task 14692 on cpu 0:
 __mod_timer+0x671/0x990 kernel/time/timer.c:1127
 mod_timer+0x1f/0x30 kernel/time/timer.c:1196
 blk_add_timer+0x222/0x2c0 block/blk-timeout.c:165
 blk_mq_start_request+0x1e5/0x3b0 block/blk-mq.c:1373
 loop_queue_rq+0x43/0x680 drivers/block/loop.c:1780
 __blk_mq_issue_directly block/blk-mq.c:2718 [inline]
 blk_mq_try_issue_directly+0x254/0x4b0 block/blk-mq.c:2778
 blk_mq_submit_bio+0xee4/0x1240 block/blk-mq.c:3242
 __submit_bio+0x54/0x3d0 block/blk-core.c:674
 __submit_bio_noacct_mq block/blk-core.c:757 [inline]
 submit_bio_noacct_nocheck+0x153/0x620 block/blk-core.c:791
 submit_bio_noacct+0x738/0x970 block/blk-core.c:929
 submit_bio+0x2a4/0x2c0 block/blk-core.c:970
 blk_crypto_submit_bio include/linux/blk-crypto.h:212 [inline]
 __bh_submit+0x373/0x3b0 fs/buffer.c:1148
 bh_submit+0x26/0x30 fs/buffer.c:1162
 __ext4_read_bh fs/ext4/super.c:192 [inline]
 ext4_read_bh+0x104/0x170 fs/ext4/super.c:217
 ext4_read_bh_lock fs/ext4/super.c:232 [inline]
 __ext4_sb_bread_gfp fs/ext4/super.c:254 [inline]
 ext4_sb_bread_unmovable+0x14b/0x180 fs/ext4/super.c:277
 ext4_load_super fs/ext4/super.c:5214 [inline]
 __ext4_fill_super fs/ext4/super.c:5420 [inline]
 ext4_fill_super+0x44b/0x37d0 fs/ext4/super.c:5899
 get_tree_bdev_flags+0x297/0x300 fs/super.c:1821
 get_tree_bdev+0x1f/0x30 fs/super.c:1844
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5931
 vfs_get_tree+0x57/0x1d0 fs/super.c:1881
 fc_mount fs/namespace.c:1282 [inline]
 do_new_mount_fc fs/namespace.c:3910 [inline]
 do_new_mount+0x288/0x730 fs/namespace.c:3986
 path_mount+0x4ad/0xba0 fs/namespace.c:4337
 do_mount fs/namespace.c:4350 [inline]
 __do_sys_mount fs/namespace.c:4563 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4540
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4540
 x64_sys_call+0xc3b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x116/0x380 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888102545e08 of 8 bytes by task 12254 on cpu 1:
 blk_add_timer+0x1b5/0x2c0 block/blk-timeout.c:-1
 blk_mq_start_request+0x1e5/0x3b0 block/blk-mq.c:1373
 loop_queue_rq+0x43/0x680 drivers/block/loop.c:1780
 __blk_mq_issue_directly block/blk-mq.c:2718 [inline]
 blk_mq_request_issue_directly+0x1f3/0x370 block/blk-mq.c:2805
 blk_mq_issue_direct+0x18a/0x4e0 block/blk-mq.c:2826
 blk_mq_dispatch_queue_requests+0x1f4/0x320 block/blk-mq.c:2901
 blk_mq_flush_plug_list+0x2ad/0x320 block/blk-mq.c:2984
 __blk_flush_plug+0x22f/0x2b0 block/blk-core.c:1274
 blk_finish_plug+0x47/0x70 block/blk-core.c:1301
 read_pages+0x4bf/0x540 mm/readahead.c:187
 page_cache_ra_unbounded+0x2cd/0x3a0 mm/readahead.c:315
 do_page_cache_ra mm/readahead.c:348 [inline]
 force_page_cache_ra+0x190/0x1d0 mm/readahead.c:378
 page_cache_sync_ra+0x11d/0x560 mm/readahead.c:602
 filemap_get_pages+0x2f2/0x1360 mm/filemap.c:2743
 filemap_read+0x21c/0xad0 mm/filemap.c:2853
 blkdev_read_iter+0x29c/0x390 block/fops.c:892
 new_sync_read fs/read_write.c:473 [inline]
 vfs_read+0x699/0x7c0 fs/read_write.c:554
 ksys_read+0xdc/0x1a0 fs/read_write.c:696
 __do_sys_read fs/read_write.c:705 [inline]
 __se_sys_read fs/read_write.c:703 [inline]
 __x64_sys_read+0x40/0x50 fs/read_write.c:703
 x64_sys_call+0x2135/0x2550 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x116/0x380 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000010000c897 -> 0x000000010000cc05

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12254 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026
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