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Date: Tue, 28 May 2024 21:46:22 -0400 From: Kent Overstreet <kent.overstreet@...ux.dev> To: syzbot <syzbot+fa3fc4c486ec9c342fcc@...kaller.appspotmail.com> Cc: bfoster@...hat.com, linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com Subject: Re: [syzbot] [bcachefs?] UBSAN: array-index-out-of-bounds in bch2_btree_path_traverse_cached_slowpath On Tue, May 28, 2024 at 01:13:23AM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 2bfcfd584ff5 Merge tag 'pmdomain-v6.10-rc1' of git://git.k.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1674fd44980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=733cc7a95171d8e7 > dashboard link: https://syzkaller.appspot.com/bug?extid=fa3fc4c486ec9c342fcc > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > userspace arch: i386 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-2bfcfd58.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/c7ed3bb80bed/vmlinux-2bfcfd58.xz > kernel image: https://storage.googleapis.com/syzbot-assets/93acc5bfbaef/bzImage-2bfcfd58.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+fa3fc4c486ec9c342fcc@...kaller.appspotmail.com > > bcachefs (loop2): journal_replay... done > bcachefs (loop2): resume_logged_ops... done > bcachefs (loop2): going read-write > bcachefs (loop2): done starting filesystem > ------------[ cut here ]------------ > UBSAN: array-index-out-of-bounds in fs/bcachefs/btree_key_cache.c:215:16 > index 66 is out of range for type 'bkey_cached *[16]' So, this is an odd one - the number of elements on the percpu freelist was somehow set to 64. And it wasn't a buffer overrun, 64 isn't a pointer. Perhaps there's a bug in the percpu allocator and it's not zeroing correctly? That would fit, since we're seeing it on startup. > CPU: 1 PID: 7694 Comm: syz-executor.2 Not tainted 6.10.0-rc1-syzkaller-00013-g2bfcfd584ff5 #0 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:114 > ubsan_epilogue lib/ubsan.c:231 [inline] > __ubsan_handle_out_of_bounds+0x110/0x150 lib/ubsan.c:429 > bkey_cached_alloc fs/bcachefs/btree_key_cache.c:215 [inline] > btree_key_cache_create fs/bcachefs/btree_key_cache.c:329 [inline] > bch2_btree_path_traverse_cached_slowpath+0x4304/0x4d90 fs/bcachefs/btree_key_cache.c:484 > bch2_btree_path_traverse_cached+0x9ec/0xdc0 fs/bcachefs/btree_key_cache.c:587 > bch2_btree_path_traverse_one+0x16b4/0x2e40 fs/bcachefs/btree_iter.c:1158 > bch2_btree_path_traverse fs/bcachefs/btree_iter.h:229 [inline] > bch2_btree_path_traverse fs/bcachefs/btree_iter.h:221 [inline] > bch2_btree_iter_peek_slot+0x715/0x2450 fs/bcachefs/btree_iter.c:2603 > __bch2_bkey_get_iter fs/bcachefs/btree_iter.h:552 [inline] > bch2_bkey_get_iter fs/bcachefs/btree_iter.h:566 [inline] > bch2_inode_peek_nowarn+0x1e3/0x390 fs/bcachefs/inode.c:340 > bch2_inode_peek fs/bcachefs/inode.c:366 [inline] > bch2_inode_find_by_inum_trans+0x125/0x2a0 fs/bcachefs/inode.c:939 > bch2_vfs_inode_get+0x41f/0x550 fs/bcachefs/fs.c:277 > bch2_mount+0xc81/0x1090 fs/bcachefs/fs.c:1999 > legacy_get_tree+0x109/0x220 fs/fs_context.c:662 > vfs_get_tree+0x8f/0x380 fs/super.c:1780 > do_new_mount fs/namespace.c:3352 [inline] > path_mount+0x6e1/0x1f10 fs/namespace.c:3679 > do_mount fs/namespace.c:3692 [inline] > __do_sys_mount fs/namespace.c:3898 [inline] > __se_sys_mount fs/namespace.c:3875 [inline] > __ia32_sys_mount+0x295/0x320 fs/namespace.c:3875 > do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline] > __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386 > do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411 > entry_SYSENTER_compat_after_hwframe+0x84/0x8e > RIP: 0023:0xf72f3579 > Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 > RSP: 002b:00000000f5ee5400 EFLAGS: 00000292 ORIG_RAX: 0000000000000015 > RAX: ffffffffffffffda RBX: 00000000f5ee5460 RCX: 0000000020011a40 > RDX: 0000000020000040 RSI: 0000000001200014 RDI: 00000000f5ee54a0 > RBP: 00000000f5ee5460 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000 > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > </TASK> > ---[ end trace ]--- > ---------------- > Code disassembly (best guess), 2 bytes skipped: > 0: 10 06 adc %al,(%rsi) > 2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi > 6: 10 07 adc %al,(%rdi) > 8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi > c: 10 08 adc %cl,(%rax) > e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi > 1e: 00 51 52 add %dl,0x52(%rcx) > 21: 55 push %rbp > 22: 89 e5 mov %esp,%ebp > 24: 0f 34 sysenter > 26: cd 80 int $0x80 > * 28: 5d pop %rbp <-- trapping instruction > 29: 5a pop %rdx > 2a: 59 pop %rcx > 2b: c3 ret > 2c: 90 nop > 2d: 90 nop > 2e: 90 nop > 2f: 90 nop > 30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi > 37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi > > > --- > 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@...glegroups.com. > > 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 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
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