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Date:   Tue, 25 Apr 2023 00:31:55 -0700
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Subject: [syzbot] [bpf?] KCSAN: data-race in __bpf_lru_list_rotate /
 __htab_lru_percpu_map_update_elem (5)
From:   syzbot <syzbot+ebe648a84e8784763f82@syzkaller.appspotmail.com>
To:     andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
        daniel@iogearbox.net, haoluo@google.com, john.fastabend@gmail.com,
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        martin.lau@linux.dev, sdf@google.com, song@kernel.org,
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Hello,

syzbot found the following issue on:

HEAD commit:    6a66fdd29ea1 Merge tag 'rust-fixes-6.3' of https://github...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=160d8948280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa4baf7c6b35b5d5
dashboard link: https://syzkaller.appspot.com/bug?extid=ebe648a84e8784763f82
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/78937867b23a/disk-6a66fdd2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dfd6c176adff/vmlinux-6a66fdd2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/51509bf47166/bzImage-6a66fdd2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ebe648a84e8784763f82@syzkaller.appspotmail.com

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

write to 0xffff888137038deb of 1 bytes by task 11240 on cpu 1:
 __bpf_lru_node_move kernel/bpf/bpf_lru_list.c:113 [inline]
 __bpf_lru_list_rotate_active kernel/bpf/bpf_lru_list.c:149 [inline]
 __bpf_lru_list_rotate+0x1bf/0x750 kernel/bpf/bpf_lru_list.c:240
 bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:329 [inline]
 bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline]
 bpf_lru_pop_free+0x638/0xe20 kernel/bpf/bpf_lru_list.c:499
 prealloc_lru_pop kernel/bpf/hashtab.c:290 [inline]
 __htab_lru_percpu_map_update_elem+0xe7/0x820 kernel/bpf/hashtab.c:1316
 bpf_percpu_hash_update+0x5e/0x90 kernel/bpf/hashtab.c:2313
 bpf_map_update_value+0x2a9/0x370 kernel/bpf/syscall.c:200
 generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1687
 bpf_map_do_batch+0x2d9/0x3d0 kernel/bpf/syscall.c:4534
 __sys_bpf+0x338/0x810
 __do_sys_bpf kernel/bpf/syscall.c:5096 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5094 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5094
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888137038deb of 1 bytes by task 11241 on cpu 0:
 bpf_lru_node_set_ref kernel/bpf/bpf_lru_list.h:70 [inline]
 __htab_lru_percpu_map_update_elem+0x2f1/0x820 kernel/bpf/hashtab.c:1332
 bpf_percpu_hash_update+0x5e/0x90 kernel/bpf/hashtab.c:2313
 bpf_map_update_value+0x2a9/0x370 kernel/bpf/syscall.c:200
 generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1687
 bpf_map_do_batch+0x2d9/0x3d0 kernel/bpf/syscall.c:4534
 __sys_bpf+0x338/0x810
 __do_sys_bpf kernel/bpf/syscall.c:5096 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5094 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5094
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11241 Comm: syz-executor.3 Not tainted 6.3.0-rc7-syzkaller-00136-g6a66fdd29ea1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
==================================================================


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