linux-kernel - Re: [syzbot] [bcachefs?] KASAN: null-ptr-deref Read in bch2_sb_set_upgrade

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Message-ID: <67190e82.050a0220.10f4f4.01ad.GAE@google.com>
Date: Wed, 23 Oct 2024 07:56:02 -0700
From: syzbot <syzbot+b468b9fef56949c3b528@...kaller.appspotmail.com>
To: aha310510@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bcachefs?] KASAN: null-ptr-deref Read in bch2_sb_set_upgrade_extra

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: null-ptr-deref Read in bch2_sb_set_upgrade_extra

bcachefs (loop0): flagging btree freespace lost data
error reading btree root freespace l=0: btree_node_read_error, fixing
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: null-ptr-deref in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: null-ptr-deref in btree_node_fake fs/bcachefs/btree_types.h:622 [inline]
BUG: KASAN: null-ptr-deref in have_stripes fs/bcachefs/sb-downgrade.c:146 [inline]
BUG: KASAN: null-ptr-deref in bch2_sb_set_upgrade_extra+0x152/0x270 fs/bcachefs/sb-downgrade.c:161
Read of size 8 at addr 00000000000000b0 by task syz.0.15/5608

CPU: 0 UID: 0 PID: 5608 Comm: syz.0.15 Not tainted 6.12.0-rc4-syzkaller-00047-gc2ee9f594da8 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_report+0xe8/0x550 mm/kasan/report.c:491
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 btree_node_fake fs/bcachefs/btree_types.h:622 [inline]
 have_stripes fs/bcachefs/sb-downgrade.c:146 [inline]
 bch2_sb_set_upgrade_extra+0x152/0x270 fs/bcachefs/sb-downgrade.c:161
 bch2_fs_recovery+0x25c4/0x39c0 fs/bcachefs/recovery.c:860
 bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1036
 bch2_fs_get_tree+0xd68/0x1710 fs/bcachefs/fs.c:2174
 vfs_get_tree+0x90/0x2b0 fs/super.c:1800
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
 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: 0033:0x7f822957f79a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f822a311e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f822a311ef0 RCX: 00007f822957f79a
RDX: 00000000200058c0 RSI: 0000000020000000 RDI: 00007f822a311eb0
RBP: 00000000200058c0 R08: 00007f822a311ef0 R09: 0000000000010000
R10: 0000000000010000 R11: 0000000000000246 R12: 0000000020000000
R13: 00007f822a311eb0 R14: 000000000000590f R15: 0000000020000140
 </TASK>
==================================================================


Tested on:

commit:         c2ee9f59 KVM: selftests: Fix build on on non-x86 archi..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ master
console output: https://syzkaller.appspot.com/x/log.txt?x=17c588a7980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fc6f8ce8c5369043
dashboard link: https://syzkaller.appspot.com/bug?extid=b468b9fef56949c3b528
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.