So this is after a bcachefs failure to mount - filesystem bringup error path - which implies we've got a memory stomper that kasan isn't able to catch. There's a couple that fit that pattern, and I think percpu allocations were involved in all of them... On Thu, Mar 06, 2025 at 11:50:20PM -0800, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 848e07631744 Merge tag 'hid-for-linus-2025030501' of git:/.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=173c4a64580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=2040405600e83619 > dashboard link: https://syzkaller.appspot.com/bug?extid=46cddce16efb51810fff > 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=10c7fda8580000 > > Downloadable assets: > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-848e0763.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/c46426c0526b/vmlinux-848e0763.xz > kernel image: https://storage.googleapis.com/syzbot-assets/d575feb1a7df/bzImage-848e0763.xz > mounted in repro: https://storage.googleapis.com/syzbot-assets/50b3934b613c/mount_0.gz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+46cddce16efb51810fff@xxxxxxxxxxxxxxxxxxxxxxxxx > > BUG: unable to handle page fault for address: ffff887fabfbcf80 > #PF: supervisor write access in kernel mode > #PF: error_code(0x0002) - not-present page > PGD 0 P4D 0 > Oops: Oops: 0002 [#1] PREEMPT SMP KASAN NOPTI > CPU: 0 UID: 0 PID: 5336 Comm: syz-executor Not tainted 6.14.0-rc5-syzkaller-00039-g848e07631744 #0 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 > RIP: 0010:__percpu_down_read_trylock kernel/locking/percpu-rwsem.c:50 [inline] > RIP: 0010:__percpu_down_read+0x40/0x130 kernel/locking/percpu-rwsem.c:169 > Code: 49 bd 00 00 00 00 00 fc ff df 4c 8d 77 68 4c 89 f5 48 c1 ed 03 42 80 7c 2d 00 00 74 08 4c 89 f7 e8 35 7e 1e f6 49 8b 44 24 68 <65> ff 00 f0 83 44 24 fc 00 49 8d 9c 24 c8 00 00 00 48 89 df be 04 > RSP: 0018:ffffc9000d1c7aa0 EFLAGS: 00010246 > RAX: ffffffff8c3bcf80 RBX: 000000008e29c24b RCX: ffff8880001fc880 > RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff8ecc2fd8 > RBP: 1ffffffff1d98608 R08: ffffffff823d3401 R09: 1ffffffff2079e8e > R10: dffffc0000000000 R11: fffffbfff2079e8f R12: ffffffff8ecc2fd8 > R13: dffffc0000000000 R14: ffffffff8ecc3040 R15: ffffffff8ecc2fd8 > FS: 0000555594365500(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff887fabfbcf80 CR3: 000000004349a000 CR4: 0000000000352ef0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > percpu_down_read_trylock include/linux/percpu-rwsem.h:84 [inline] > __sb_start_write_trylock include/linux/fs.h:1790 [inline] > sb_start_write_trylock include/linux/fs.h:1926 [inline] > pipe_write+0x16db/0x1950 fs/pipe.c:605 > new_sync_write fs/read_write.c:586 [inline] > vfs_write+0xacf/0xd10 fs/read_write.c:679 > ksys_write+0x18f/0x2b0 fs/read_write.c:731 > 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: 0033:0x7fc094d8bbe0 > Code: 40 00 48 c7 c2 a8 ff ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 80 3d 61 19 1f 00 00 74 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 28 48 89 > RSP: 002b:00007ffe88624b48 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 > RAX: ffffffffffffffda RBX: 0000555594379d50 RCX: 00007fc094d8bbe0 > RDX: 0000000000000030 RSI: 00007ffe88624b80 RDI: 000000000000000b > RBP: 0000555594378f20 R08: 0000000005a61143 R09: 7fffffffffffffff > R10: 00007fc095b50038 R11: 0000000000000202 R12: 0000000000000001 > R13: 0000000000000000 R14: 00007ffe88624b60 R15: 0000000000000000 > </TASK> > Modules linked in: > CR2: ffff887fabfbcf80 > ---[ end trace 0000000000000000 ]--- > RIP: 0010:__percpu_down_read_trylock kernel/locking/percpu-rwsem.c:50 [inline] > RIP: 0010:__percpu_down_read+0x40/0x130 kernel/locking/percpu-rwsem.c:169 > Code: 49 bd 00 00 00 00 00 fc ff df 4c 8d 77 68 4c 89 f5 48 c1 ed 03 42 80 7c 2d 00 00 74 08 4c 89 f7 e8 35 7e 1e f6 49 8b 44 24 68 <65> ff 00 f0 83 44 24 fc 00 49 8d 9c 24 c8 00 00 00 48 89 df be 04 > RSP: 0018:ffffc9000d1c7aa0 EFLAGS: 00010246 > RAX: ffffffff8c3bcf80 RBX: 000000008e29c24b RCX: ffff8880001fc880 > RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff8ecc2fd8 > RBP: 1ffffffff1d98608 R08: ffffffff823d3401 R09: 1ffffffff2079e8e > R10: dffffc0000000000 R11: fffffbfff2079e8f R12: ffffffff8ecc2fd8 > R13: dffffc0000000000 R14: ffffffff8ecc3040 R15: ffffffff8ecc2fd8 > FS: 0000555594365500(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff887fabfbcf80 CR3: 000000004349a000 CR4: 0000000000352ef0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > ---------------- > Code disassembly (best guess): > 0: 49 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%r13 > 7: fc ff df > a: 4c 8d 77 68 lea 0x68(%rdi),%r14 > e: 4c 89 f5 mov %r14,%rbp > 11: 48 c1 ed 03 shr $0x3,%rbp > 15: 42 80 7c 2d 00 00 cmpb $0x0,0x0(%rbp,%r13,1) > 1b: 74 08 je 0x25 > 1d: 4c 89 f7 mov %r14,%rdi > 20: e8 35 7e 1e f6 call 0xf61e7e5a > 25: 49 8b 44 24 68 mov 0x68(%r12),%rax > * 2a: 65 ff 00 incl %gs:(%rax) <-- trapping instruction > 2d: f0 83 44 24 fc 00 lock addl $0x0,-0x4(%rsp) > 33: 49 8d 9c 24 c8 00 00 lea 0xc8(%r12),%rbx > 3a: 00 > 3b: 48 89 df mov %rbx,%rdi > 3e: be .byte 0xbe > 3f: 04 .byte 0x4 > > > --- > 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. > > 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
