KCSAN: data-race in _copy_to

Kernel	Title	Rank 🛈	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in _copy_to_iter / string (2) ext4	6	2	671d	690d	0/29	auto-obsoleted due to no activity on 2024/05/15 22:06
upstream	KCSAN: data-race in _copy_to_iter / string (4) ext4	6	1	406d	406d	0/29	auto-obsoleted due to no activity on 2025/02/26 06:42
upstream	KCSAN: data-race in _copy_to_iter / string (3) ext4	6	2	531d	538d	0/29	auto-obsoleted due to no activity on 2024/10/03 11:49
upstream	KCSAN: data-race in _copy_to_iter / string ext4	6	1	751d	751d	0/29	auto-obsoleted due to no activity on 2024/02/26 12:58

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BUG: KCSAN: data-race in _copy_to_iter / string

write to 0xffff88811d0c3050 of 1 bytes by task 25852 on cpu 1:
 string_nocheck lib/vsprintf.c:658 [inline]
 string+0x187/0x220 lib/vsprintf.c:736
 bdev_name+0xd7/0x2b0 lib/vsprintf.c:976
 pointer+0x549/0xcb0 lib/vsprintf.c:2587
 vsnprintf+0x491/0x860 lib/vsprintf.c:2951
 snprintf+0x86/0xb0 lib/vsprintf.c:3041
 ext4_multi_mount_protect+0x4e4/0x600 fs/ext4/mmp.c:382
 __ext4_fill_super fs/ext4/super.c:5454 [inline]
 ext4_fill_super+0x2334/0x3800 fs/ext4/super.c:5777
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1691
 get_tree_bdev+0x1f/0x30 fs/super.c:1714
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5809
 vfs_get_tree+0x57/0x1d0 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount+0x288/0x700 fs/namespace.c:3712
 path_mount+0x4d0/0xbc0 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4201
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4201
 x64_sys_call+0x2cca/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811d0c3000 of 512 bytes by task 23051 on cpu 0:
 instrument_copy_to_user include/linux/instrumented.h:113 [inline]
 copy_to_user_iter lib/iov_iter.c:24 [inline]
 iterate_ubuf include/linux/iov_iter.h:30 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:302 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 _copy_to_iter+0x130/0xea0 lib/iov_iter.c:197
 copy_page_to_iter+0x18f/0x2d0 lib/iov_iter.c:374
 copy_folio_to_iter include/linux/uio.h:204 [inline]
 filemap_read+0x407/0xa10 mm/filemap.c:2851
 blkdev_read_iter+0x22d/0x2e0 block/fops.c:856
 new_sync_read fs/read_write.c:491 [inline]
 vfs_read+0x6c0/0x7f0 fs/read_write.c:572
 ksys_read+0xdc/0x1a0 fs/read_write.c:715
 __do_sys_read fs/read_write.c:724 [inline]
 __se_sys_read fs/read_write.c:722 [inline]
 __x64_sys_read+0x40/0x50 fs/read_write.c:722
 x64_sys_call+0x2889/0x3000 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 23051 Comm: udevd Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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