[moderation] [mm?] upstream test error: KCSAN: data-race in __percpu_counter_limited_add / __percpu_counter_limited_add (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cee73b1e840c Merge tag 'riscv-for-linus-7.0-mw1' of git://..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15162c02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a6d4a8c8877f1220
dashboard link: https://syzkaller.appspot.com/bug?extid=6de02af21cddc23978c4
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [ak...@linux-foundation.org baoli...@linux.alibaba.com hu...@google.com linux-...@vger.kernel.org linu...@kvack.org]

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/44d358a87145/disk-cee73b1e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aa4f49ab62ae/vmlinux-cee73b1e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2735d7f69896/bzImage-cee73b1e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6de02a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __percpu_counter_limited_add / __percpu_counter_limited_add

write to 0xffff88810d329910 of 8 bytes by task 3501 on cpu 0:
__percpu_counter_limited_add+0x38c/0x400 lib/percpu_counter.c:386
percpu_counter_limited_add include/linux/percpu_counter.h:77 [inline]
shmem_inode_acct_blocks+0xf4/0x230 mm/shmem.c:232
shmem_alloc_and_add_folio mm/shmem.c:2002 [inline]
shmem_get_folio_gfp+0x5b2/0xd60 mm/shmem.c:2567
shmem_get_folio mm/shmem.c:2673 [inline]
shmem_write_begin+0xfc/0x1f0 mm/shmem.c:3326
generic_perform_write+0x183/0x490 mm/filemap.c:4314
shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3501
__kernel_write_iter+0x319/0x590 fs/read_write.c:621
dump_emit_page fs/coredump.c:1299 [inline]
dump_user_range+0xa7d/0xdb0 fs/coredump.c:1373
elf_core_dump+0x21a2/0x2330 fs/binfmt_elf.c:2111
coredump_write+0xacf/0xdf0 fs/coredump.c:1050
do_coredump fs/coredump.c:1127 [inline]
vfs_coredump+0x26c7/0x3130 fs/coredump.c:1201
get_signal+0xd7b/0xf60 kernel/signal.c:3019
arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop kernel/entry/common.c:98 [inline]
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline]
irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline]
irqentry_exit+0xf7/0x520 kernel/entry/common.c:219
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

read to 0xffff88810d329910 of 8 bytes by task 3655 on cpu 1:
__percpu_counter_limited_add+0xc0/0x400 lib/percpu_counter.c:-1
percpu_counter_limited_add include/linux/percpu_counter.h:77 [inline]
shmem_inode_acct_blocks+0xf4/0x230 mm/shmem.c:232
shmem_alloc_and_add_folio mm/shmem.c:2002 [inline]
shmem_get_folio_gfp+0x5b2/0xd60 mm/shmem.c:2567
shmem_get_folio mm/shmem.c:2673 [inline]
shmem_write_begin+0xfc/0x1f0 mm/shmem.c:3326
generic_perform_write+0x183/0x490 mm/filemap.c:4314
shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3501
__kernel_write_iter+0x319/0x590 fs/read_write.c:621
dump_emit_page fs/coredump.c:1299 [inline]
dump_user_range+0xa7d/0xdb0 fs/coredump.c:1373
elf_core_dump+0x21a2/0x2330 fs/binfmt_elf.c:2111
coredump_write+0xacf/0xdf0 fs/coredump.c:1050
do_coredump fs/coredump.c:1127 [inline]
vfs_coredump+0x26c7/0x3130 fs/coredump.c:1201
get_signal+0xd7b/0xf60 kernel/signal.c:3019
arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000001e8d -> 0x0000000000001eae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3655 Comm: syz.3.320 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
==================================================================
syz.3.320 (3655) used greatest stack depth: 9856 bytes left


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