[moderation] [bpf?] KCSAN: data-race in __bpf_lru_list_rotate / bpf_lru_push_free (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 551c722f4080 Merge tag 'rtc-7.3-fixes' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=100466c9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ea1e6d8de13bab08
dashboard link: https://syzkaller.appspot.com/bug?extid=1ea4f564bf6f1f3d1dc4
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [and...@kernel.org a...@kernel.org b...@vger.kernel.org dan...@iogearbox.net edd...@gmail.com em...@etsalapatis.com ihor.s...@linux.dev jo...@kernel.org linux-...@vger.kernel.org marti...@linux.dev mem...@gmail.com so...@kernel.org yongho...@linux.dev]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a6b05bccc40f/disk-551c722f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5a247a4f5187/vmlinux-551c722f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5a6d70478180/bzImage-551c722f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1ea4f5...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __bpf_lru_list_rotate / bpf_lru_push_free

write to 0xffff88811b758022 of 1 bytes by task 4756 on cpu 1:
__bpf_lru_node_move kernel/bpf/bpf_lru_list.c:97 [inline]
__bpf_lru_list_rotate_active kernel/bpf/bpf_lru_list.c:137 [inline]
__bpf_lru_list_rotate+0x2e6/0x750 kernel/bpf/bpf_lru_list.c:228
bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:325 [inline]
bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:453 [inline]
bpf_lru_pop_free+0xa62/0x1cf0 kernel/bpf/bpf_lru_list.c:522
prealloc_lru_pop kernel/bpf/hashtab.c:306 [inline]
htab_lru_map_update_elem+0xe0/0x6d0 kernel/bpf/hashtab.c:1316
bpf_map_update_value+0x4ee/0x570 kernel/bpf/syscall.c:297
generic_map_update_batch+0x4d7/0x700 kernel/bpf/syscall.c:2106
bpf_map_do_batch+0x25b/0x380 kernel/bpf/syscall.c:5781
__sys_bpf+0xa8e/0xc30 kernel/bpf/syscall.c:-1
__do_sys_bpf kernel/bpf/syscall.c:6489 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6486 [inline]
__x64_sys_bpf+0x69/0x80 kernel/bpf/syscall.c:6486
x64_sys_call+0xf26/0x2550 arch/x86/include/generated/asm/syscalls_64.h:322
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b758022 of 1 bytes by task 4752 on cpu 0:
bpf_lru_list_push_free kernel/bpf/bpf_lru_list.c:301 [inline]
bpf_common_lru_push_free kernel/bpf/bpf_lru_list.c:562 [inline]
bpf_lru_push_free+0xc68/0xda0 kernel/bpf/bpf_lru_list.c:588
htab_lru_push_free+0x17d/0x1a0 kernel/bpf/hashtab.c:1284
htab_lru_map_update_elem+0x642/0x6d0 kernel/bpf/hashtab.c:1348
bpf_map_update_value+0x4ee/0x570 kernel/bpf/syscall.c:297
generic_map_update_batch+0x4d7/0x700 kernel/bpf/syscall.c:2106
bpf_map_do_batch+0x25b/0x380 kernel/bpf/syscall.c:5781
__sys_bpf+0xa8e/0xc30 kernel/bpf/syscall.c:-1
__do_sys_bpf kernel/bpf/syscall.c:6489 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6486 [inline]
__x64_sys_bpf+0x69/0x80 kernel/bpf/syscall.c:6486
x64_sys_call+0xf26/0x2550 arch/x86/include/generated/asm/syscalls_64.h:322
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4752 Comm: syz.1.522 Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================


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