[v2] jfs: UBSAN: shift-out-of-bounds in dbFindBits

[PATCH v2] jfs: UBSAN: shift-out-of-bounds in dbFindBits

Posted by Matt Jan 1 month ago

The starting bit number of free bits should not be >= 32 as it is
0-indexed.Assert that the number of bits is < 32, or if it is 32, the
input word must be 0.

#syz test

Reported-by: syzbot+9e90a1c5eedb9dc4c6cc@syzkaller.appspotmail.com
Signed-off-by: Matt Jan <zoo868e@gmail.com>
---
Changes in v2: Test if the patch resolve the issue through syzbot and
reference the reporter.

 fs/jfs/jfs_dmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 974ecf5e0d95..b9eccf8900eb 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -3015,7 +3015,7 @@ static int dbFindBits(u32 word, int l2nb)
 	/* get the number of bits.
 	 */
 	nb = 1 << l2nb;
-	assert(nb <= DBWORD);
+	assert(nb < DBWORD || (nb == DBWORD && !word));
 
 	/* complement the word so we can use a mask (i.e. 0s represent
 	 * free bits) and compute the mask.
-- 
2.25.1

Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in dbFindBits (2)

Posted by syzbot 1 month ago

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in dbFindBits

ERROR: (device loop0): dbAllocBits: leaf page corrupt
BUG at fs/jfs/jfs_dmap.c:3018 assert(nb < DBWORD || (nb == DBWORD && !word))
------------[ cut here ]------------
kernel BUG at fs/jfs/jfs_dmap.c:3018!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5606 Comm: syz.0.15 Not tainted 6.12.0-rc4-syzkaller-00161-gae90f6a6170d-dirty #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:dbFindBits+0x1dc/0x210 fs/jfs/jfs_dmap.c:3018
Code: e9 fa fe ff ff e8 74 40 68 fe 48 c7 c7 00 33 43 8c 48 c7 c6 40 30 43 8c ba ca 0b 00 00 48 c7 c1 c0 3a 43 8c e8 65 30 97 08 90 <0f> 0b e8 4d 40 68 fe 48 c7 c7 00 33 43 8c 48 c7 c6 40 30 43 8c ba
RSP: 0018:ffffc9000b107940 EFLAGS: 00010246
RAX: 000000000000004c RBX: ffff88801f140800 RCX: 37b0eb8928fc2800
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000020 R08: ffffffff81749f8c R09: 1ffff92001620ec4
R10: dffffc0000000000 R11: fffff52001620ec5 R12: 0000000000000020
R13: 1ffff92001620f38 R14: 00000000ffffffff R15: 0000000000000005
FS:  00007fd1f83196c0(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ea5ffff CR3: 00000000415e4000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 dbAllocDmapLev+0x1e9/0x4a0 fs/jfs/jfs_dmap.c:1985
 dbAllocCtl+0x113/0x920 fs/jfs/jfs_dmap.c:1825
 dbAllocAG+0x28f/0x10b0 fs/jfs/jfs_dmap.c:1364
 dbDiscardAG+0x352/0xa20 fs/jfs/jfs_dmap.c:1613
 jfs_ioc_trim+0x45a/0x6b0 fs/jfs/jfs_discard.c:105
 jfs_ioctl+0x2cd/0x3e0 fs/jfs/ioctl.c:131
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
 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: 0033:0x7fd1f757dff9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd1f8319038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd1f7735f80 RCX: 00007fd1f757dff9
RDX: 00000000200000c0 RSI: 00000000c0185879 RDI: 0000000000000004
RBP: 00007fd1f75f0296 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fd1f7735f80 R15: 00007ffdd2e520e8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dbFindBits+0x1dc/0x210 fs/jfs/jfs_dmap.c:3018
Code: e9 fa fe ff ff e8 74 40 68 fe 48 c7 c7 00 33 43 8c 48 c7 c6 40 30 43 8c ba ca 0b 00 00 48 c7 c1 c0 3a 43 8c e8 65 30 97 08 90 <0f> 0b e8 4d 40 68 fe 48 c7 c7 00 33 43 8c 48 c7 c6 40 30 43 8c ba
RSP: 0018:ffffc9000b107940 EFLAGS: 00010246
RAX: 000000000000004c RBX: ffff88801f140800 RCX: 37b0eb8928fc2800
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000020 R08: ffffffff81749f8c R09: 1ffff92001620ec4
R10: dffffc0000000000 R11: fffff52001620ec5 R12: 0000000000000020
R13: 1ffff92001620f38 R14: 00000000ffffffff R15: 0000000000000005
FS:  00007fd1f83196c0(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ea5ffff CR3: 00000000415e4000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


Tested on:

commit:         ae90f6a6 Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=166868a7980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fc6f8ce8c5369043
dashboard link: https://syzkaller.appspot.com/bug?extid=9e90a1c5eedb9dc4c6cc
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10a7de40580000