Subject: Re: [syzbot] [bpf?] BUG: using smp_processor_id() in preemptible code in bpf_mem_alloc

From: Yonghong Song <[email-masked]>
Date: Mon, 18 Nov 2024 08:30:32 -0800

#syz fix: bpf: Add necessary migrate_disable to range_tree.

On 11/18/24 2:20 AM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    379d5ee624ed Merge branch 'bpf-range_tree-for-bpf-arena'
> git tree:       bpf-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=115ecb5f980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d2aeec8c0b2e420c
> dashboard link: https://syzkaller.appspot.com/bug?extid=fd2873203c2ed428828a
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12636ce8580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11f0f4c0580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/e83cf63a68cf/disk-379d5ee6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/ff1f89f228ad/vmlinux-379d5ee6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/8a715c466ecd/bzImage-379d5ee6.xz
>
> The issue was bisected to:
>
> commit b795379757eb054925fbb6783559c86f01c1a614
> Author: Alexei Starovoitov <[email-masked]>
> Date:   Fri Nov 8 02:56:15 2024 +0000
>
>      bpf: Introduce range_tree data structure and use it in bpf arena
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10b2ab5f980000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=12b2ab5f980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=14b2ab5f980000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email-masked]
> Fixes: b795379757eb ("bpf: Introduce range_tree data structure and use it in bpf arena")
>
> BUG: using smp_processor_id() in preemptible [00000000] code: syz-executor373/5838
> caller is bpf_mem_alloc+0x117/0x220 kernel/bpf/memalloc.c:903
> CPU: 1 UID: 0 PID: 5838 Comm: syz-executor373 Not tainted 6.12.0-rc7-syzkaller-g379d5ee624ed #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
> Call Trace:
>   <TASK>
>   __dump_stack lib/dump_stack.c:94 [inline]
>   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
>   check_preemption_disabled+0x10e/0x120 lib/smp_processor_id.c:49
>   bpf_mem_alloc+0x117/0x220 kernel/bpf/memalloc.c:903
>   range_tree_set+0x971/0x1830 kernel/bpf/range_tree.c:238
>   arena_map_alloc+0x36f/0x440 kernel/bpf/arena.c:137
>   map_create+0x946/0x11c0 kernel/bpf/syscall.c:1441
>   __sys_bpf+0x6d1/0x810 kernel/bpf/syscall.c:5741
>   __do_sys_bpf kernel/bpf/syscall.c:5866 [inline]
>   __se_sys_bpf kernel/bpf/syscall.c:5864 [inline]
>   __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5864
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f5cb29a1329
> Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffee3bcaa18 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 00007ffee3bcabf8 RCX: 00007f5cb29a1329
> RDX: 0000000000000048 RSI: 0000000020003940 RDI: 0000000000000000
> RBP: 00007f5cb2a14610 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffee3bcabe8 R14: 0000000000000001 R15: 0000000000000001
>   </TA
>
>
> ---
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