Re: [syzbot] [mm?] KCSAN: data-race in generic_fillattr / shmem_mknod (2)

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KCSAN: data-race in pcpu_alloc_noprof / pcpu_free_area

==================================================================
BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_free_area

read-write to 0xffffffff883f872c of 4 bytes by task 3378 on cpu 0:
 pcpu_update_empty_pages mm/percpu.c:602 [inline]
 pcpu_block_update_hint_free mm/percpu.c:1044 [inline]
 pcpu_free_area+0x4dc/0x570 mm/percpu.c:1302
 free_percpu+0x1c6/0xb30 mm/percpu.c:2277
 xt_percpu_counter_free+0x63/0x80 net/netfilter/x_tables.c:1951
 cleanup_entry+0x195/0x1c0 net/ipv6/netfilter/ip6_tables.c:671
 __do_replace+0x470/0x580 net/ipv6/netfilter/ip6_tables.c:1099
 do_replace net/ipv6/netfilter/ip6_tables.c:1158 [inline]
 do_ip6t_set_ctl+0x820/0x8c0 net/ipv6/netfilter/ip6_tables.c:1644
 nf_setsockopt+0x195/0x1b0 net/netfilter/nf_sockopt.c:101
 ipv6_setsockopt+0x126/0x140 net/ipv6/ipv6_sockglue.c:998
 tcp_setsockopt+0x93/0xb0 net/ipv4/tcp.c:3768
 sock_common_setsockopt+0x64/0x80 net/core/sock.c:3735
 do_sock_setsockopt net/socket.c:2324 [inline]
 __sys_setsockopt+0x1d8/0x250 net/socket.c:2347
 __do_sys_setsockopt net/socket.c:2356 [inline]
 __se_sys_setsockopt net/socket.c:2353 [inline]
 __x64_sys_setsockopt+0x66/0x80 net/socket.c:2353
 x64_sys_call+0x278d/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:55
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x54/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

read to 0xffffffff883f872c of 4 bytes by task 3374 on cpu 1:
 pcpu_alloc_noprof+0x9a5/0x10c0 mm/percpu.c:1894
 xt_percpu_counter_alloc+0x79/0x110 net/netfilter/x_tables.c:1931
 find_check_entry net/ipv4/netfilter/ip_tables.c:526 [inline]
 translate_table+0x921/0xf70 net/ipv4/netfilter/ip_tables.c:716
 do_replace net/ipv4/netfilter/ip_tables.c:1137 [inline]
 do_ipt_set_ctl+0x7bd/0x8b0 net/ipv4/netfilter/ip_tables.c:1635
 nf_setsockopt+0x195/0x1b0 net/netfilter/nf_sockopt.c:101
 ip_setsockopt+0xea/0x100 net/ipv4/ip_sockglue.c:1424
 tcp_setsockopt+0x93/0xb0 net/ipv4/tcp.c:3768
 sock_common_setsockopt+0x64/0x80 net/core/sock.c:3735
 do_sock_setsockopt net/socket.c:2324 [inline]
 __sys_setsockopt+0x1d8/0x250 net/socket.c:2347
 __do_sys_setsockopt net/socket.c:2356 [inline]
 __se_sys_setsockopt net/socket.c:2353 [inline]
 __x64_sys_setsockopt+0x66/0x80 net/socket.c:2353
 x64_sys_call+0x278d/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:55
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x54/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

value changed: 0x00000005 -> 0x00000006

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3374 Comm: syz-executor.3 Not tainted 6.11.0-rc6-syzkaller-00326-gd1f2d51b711a-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
==================================================================


Tested on:

commit:         d1f2d51b Merge tag 'clk-fixes-for-linus' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10691ffb980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e81d40b0108ea8fe
dashboard link: https://syzkaller.appspot.com/bug?extid=702361cf7e3d95758761
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=117d8877980000