[syzbot] [bcachefs?] KASAN: null-ptr-deref Read in bch2_sb_set_upgrade_extra

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b04ae0f45168 Merge tag 'v6.12-rc3-smb3-client-fixes' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14687487980000
kernel config: https://syzkaller.appspot.com/x/.config?x=cfbd94c114a3d407
dashboard link: https://syzkaller.appspot.com/bug?extid=b468b9fef56949c3b528
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=14667c5f980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11e18430580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-b04ae0f4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3e40a4ec7885/vmlinux-b04ae0f4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9312d8ec05d3/bzImage-b04ae0f4.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/3495c223c477/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b468b9...@syzkaller.appspotmail.com

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-executor407/5095

CPU: 0 UID: 0 PID: 5095 Comm: syz-executor407 Not tainted 6.12.0-rc3-syzkaller-00319-gb04ae0f45168 #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:4055 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4032
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: 0033:0x7ff4b3b479ba
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe3df5ae28 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe3df5ae40 RCX: 00007ff4b3b479ba
RDX: 00000000200058c0 RSI: 0000000020000000 RDI: 00007ffe3df5ae40
RBP: 0000000000000004 R08: 00007ffe3df5ae80 R09: 0000000000005909
R10: 0000000000010000 R11: 0000000000000282 R12: 0000000000010000
R13: 00007ffe3df5ae80 R14: 0000000000000003 R15: 0000000001000000
</TASK>
==================================================================


---
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 syzk...@googlegroups.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 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

[syzbot]

For archival purposes, forwarding an incoming command email to
syzkall...@googlegroups.com.

***

Subject: Re: [syzbot] [bcachefs?] KASAN: null-ptr-deref Read in bch2_sb_set_upgrade_extra
Author: aha3...@gmail.com

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ master

[syzbot]

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.

[syzbot]

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

---
fs/bcachefs/sb-downgrade.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/bcachefs/sb-downgrade.c b/fs/bcachefs/sb-downgrade.c
index ae715ff658e8..8767c33c2b51 100644
--- a/fs/bcachefs/sb-downgrade.c
+++ b/fs/bcachefs/sb-downgrade.c
@@ -143,6 +143,9 @@ UPGRADE_TABLE()

static int have_stripes(struct bch_fs *c)
{
+ if (IS_ERR_OR_NULL(c->btree_roots_known[BTREE_ID_stripes].b))
+ return 0;
+
return !btree_node_fake(c->btree_roots_known[BTREE_ID_stripes].b);
}

--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+b468b9...@syzkaller.appspotmail.com
Tested-by: syzbot+b468b9...@syzkaller.appspotmail.com

Tested on:

commit: c2ee9f59 KVM: selftests: Fix build on on non-x86 archi..

git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11e5c287980000

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

patch: https://syzkaller.appspot.com/x/patch.diff?x=14fe4c30580000

Note: testing is done by a robot and is best-effort only.