Jesper,
I think 21c38a3bd4ee ("cgroup/rstat: add cgroup_rstat_cpu_lock helpers and
tracepoints") is the offending commit for the following syzbot report. In
cgroup creation failure path, cgroup_rstat_exit() is called with @cgrp which
is not fully initialized / partially destroyed, which calls
__cgroup_rstat_lock() which then triggers a tracepoint which tries to deref
a NULL pointer. We'll probably have to flag this path and avoid triggering
the TP. Can you please take a look?
Thanks.
On Thu, Dec 05, 2024 at 09:48:25AM -0800, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 932fc2f19b74 Merge branch 'irq-save-restore'
> git tree: bpf-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14fd6330580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=50c7a61469ce77e7
> dashboard link: https://syzkaller.appspot.com/bug?extid=31eb4d4e7d9bc1fc1312
> 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=161cdfc0580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12dfc8df980000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/afd76657938b/disk-932fc2f1.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/5ab299e9b5df/vmlinux-932fc2f1.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/6617519fa7b9/bzImage-932fc2f1.xz
>
> Bisection is inconclusive: the first bad commit could be any of:
>
> 42d9e8b7ccdd Merge tag 'powerpc-6.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
> 9f16d5e6f220 Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=121e8020580000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+31eb4d4e7d9bc1fc1312@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> RBP: 0000000000000001 R08: 00007ffee33edd87 R09: 00007fe28ebf71e7
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffee33ee00c
> R13: 00007ffee33ee030 R14: 00007ffee33ee070 R15: 0000000000000001
> </TASK>
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> CPU: 1 UID: 0 PID: 5842 Comm: syz-executor126 Not tainted 6.13.0-rc1-syzkaller-00032-g932fc2f19b74 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> RIP: 0010:do_perf_trace_cgroup_rstat include/trace/events/cgroup.h:207 [inline]
> RIP: 0010:perf_trace_cgroup_rstat+0x2b2/0x580 include/trace/events/cgroup.h:207
> Code: 8d 98 58 04 00 00 48 89 d8 48 c1 e8 03 42 80 3c 30 00 74 08 48 89 df e8 fc 0c 75 00 48 8b 1b 48 83 c3 0c 48 89 d8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 0f 85 d5 01 00 00 44 8b 2b 49 8d 5f 08 48 89
> RSP: 0018:ffffc90003837a80 EFLAGS: 00010003
> RAX: 0000000000000001 RBX: 000000000000000c RCX: ffff8880345ada00
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8880b8737768
> RBP: ffffc90003837b70 R08: ffffffff81a90e9b R09: 1ffffffff20328d6
> R10: dffffc0000000000 R11: fffffbfff20328d7 R12: ffff8880b87376e0
> R13: 1ffff92000706f5c R14: dffffc0000000000 R15: ffffe8ffffd30be8
> FS: 000055558b3013c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000002000050c CR3: 00000000329de000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> trace_cgroup_rstat_locked include/trace/events/cgroup.h:242 [inline]
> __cgroup_rstat_lock+0x3e1/0x590 kernel/cgroup/rstat.c:292
> cgroup_rstat_flush+0x30/0x50 kernel/cgroup/rstat.c:353
> cgroup_rstat_exit+0x27/0x1e0 kernel/cgroup/rstat.c:411
> cgroup_create kernel/cgroup/cgroup.c:5782 [inline]
> cgroup_mkdir+0x53a/0xd60 kernel/cgroup/cgroup.c:5831
> kernfs_iop_mkdir+0x253/0x3f0 fs/kernfs/dir.c:1246
> vfs_mkdir+0x2f9/0x4f0 fs/namei.c:4311
> do_mkdirat+0x264/0x3a0 fs/namei.c:4334
> __do_sys_mkdir fs/namei.c:4354 [inline]
> __se_sys_mkdir fs/namei.c:4352 [inline]
> __x64_sys_mkdir+0x6c/0x80 fs/namei.c:4352
> 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: 0033:0x7fe28eba7a19
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 81 1d 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffee33edfe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fe28eba7a19
> RDX: 0000000000000000 RSI: d0939199c36b4d28 RDI: 0000000020000000
> RBP: 0000000000000001 R08: 00007ffee33edd87 R09: 00007fe28ebf71e7
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffee33ee00c
> R13: 00007ffee33ee030 R14: 00007ffee33ee070 R15: 0000000000000001
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:do_perf_trace_cgroup_rstat include/trace/events/cgroup.h:207 [inline]
> RIP: 0010:perf_trace_cgroup_rstat+0x2b2/0x580 include/trace/events/cgroup.h:207
> Code: 8d 98 58 04 00 00 48 89 d8 48 c1 e8 03 42 80 3c 30 00 74 08 48 89 df e8 fc 0c 75 00 48 8b 1b 48 83 c3 0c 48 89 d8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 0f 85 d5 01 00 00 44 8b 2b 49 8d 5f 08 48 89
> RSP: 0018:ffffc90003837a80 EFLAGS: 00010003
> RAX: 0000000000000001 RBX: 000000000000000c RCX: ffff8880345ada00
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8880b8737768
> RBP: ffffc90003837b70 R08: ffffffff81a90e9b R09: 1ffffffff20328d6
> R10: dffffc0000000000 R11: fffffbfff20328d7 R12: ffff8880b87376e0
> R13: 1ffff92000706f5c R14: dffffc0000000000 R15: ffffe8ffffd30be8
> FS: 000055558b3013c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000002000050c CR3: 00000000329de000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
> 0: 8d 98 58 04 00 00 lea 0x458(%rax),%ebx
> 6: 48 89 d8 mov %rbx,%rax
> 9: 48 c1 e8 03 shr $0x3,%rax
> d: 42 80 3c 30 00 cmpb $0x0,(%rax,%r14,1)
> 12: 74 08 je 0x1c
> 14: 48 89 df mov %rbx,%rdi
> 17: e8 fc 0c 75 00 call 0x750d18
> 1c: 48 8b 1b mov (%rbx),%rbx
> 1f: 48 83 c3 0c add $0xc,%rbx
> 23: 48 89 d8 mov %rbx,%rax
> 26: 48 c1 e8 03 shr $0x3,%rax
> * 2a: 42 0f b6 04 30 movzbl (%rax,%r14,1),%eax <-- trapping instruction
> 2f: 84 c0 test %al,%al
> 31: 0f 85 d5 01 00 00 jne 0x20c
> 37: 44 8b 2b mov (%rbx),%r13d
> 3a: 49 8d 5f 08 lea 0x8(%r15),%rbx
> 3e: 48 rex.W
> 3f: 89 .byte 0x89
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
--
tejun
