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

Hello,

syzbot found the following issue on:

HEAD commit: c2ee9f594da8 KVM: selftests: Fix build on on non-x86 archi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=134fc640580000
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
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=118f0287980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=128f8a5f980000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-c2ee9f59.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8a3541902b13/vmlinux-c2ee9f59.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a00efacc2604/bzImage-c2ee9f59.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/0a96c5cc2569/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

ERROR: (device loop0): remounting filesystem as read-only
ERROR: (device loop0): dbDiscardAG: -EIO
ERROR: (device loop0): dbAllocBits: leaf page corrupt
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/jfs/jfs_dmap.c:3028:55
shift exponent 32 is too large for 32-bit type 'u32' (aka 'unsigned int')
CPU: 0 UID: 0 PID: 5092 Comm: syz-executor128 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
ubsan_epilogue lib/ubsan.c:231 [inline]
__ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
dbFindBits+0x11a/0x1d0 fs/jfs/jfs_dmap.c:3028
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: 0033:0x7f54e7034c99
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd37b5c358 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f54e7034c99
RDX: 00000000200000c0 RSI: 00000000c0185879 RDI: 0000000000000004
RBP: 00007f54e70ad5f0 R08: 000055557b4874c0 R09: 000055557b4874c0
R10: 000055557b4874c0 R11: 0000000000000246 R12: 00007ffd37b5c380
R13: 00007ffd37b5c5a8 R14: 431bde82d7b634db R15: 00007f54e707d03b
</TASK>
---[ end trace ]---


---
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 [email protected].

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If the report is already addressed, let syzbot know by replying with:
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***

Subject: [PATCH v2] jfs: UBSAN: shift-out-of-bounds in dbFindBits
Author: [email protected]

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: [email protected]
Signed-off-by: Matt Jan <[email protected]>
---
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

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in dbFindBits
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
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>
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
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
patch: https://syzkaller.appspot.com/x/patch.diff?x=10a7de40580000

[email protected], [email protected].

***

Subject: [PATCH v3] jfs: UBSAN: shift-out-of-bounds in dbFindBits
Changes in v3: return the result earlier instead of assert
fs/jfs/jfs_dmap.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 974ecf5e0d95..346f2617b744 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -3017,6 +3017,9 @@ static int dbFindBits(u32 word, int l2nb)
nb = 1 << l2nb;
assert(nb <= DBWORD);

+ if (nb == DBWORD)
+ return (!!word) << BUDMIN;
+
*/
--
2.25.1

Hello,

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

Reported-by: [email protected]
Tested-by: [email protected]
console output: https://syzkaller.appspot.com/x/log.txt?x=17968230580000
patch: https://syzkaller.appspot.com/x/patch.diff?x=1231b287980000

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

Return immediately if the needed free bits span a full word to avoid
out-of-bounds shifting.
Changes in v3: Return the result earlier instead of assert it
fs/jfs/jfs_dmap.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 974ecf5e0d95..45b7a393b769 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -3012,6 +3012,11 @@ static int dbFindBits(u32 word, int l2nb)
int bitno, nb;
u32 mask;

+ /* return immediately if the number of free bits is a word
+ */
+ if (l2nb == BUDMIN)
--
2.25.1

console output: https://syzkaller.appspot.com/x/log.txt?x=1274aebb980000
patch: https://syzkaller.appspot.com/x/patch.diff?x=1254aebb980000

Subject: [PATCH v4] jfs: UBSAN: shift-out-of-bounds in dbFindBits
Author: [email protected]

Ensure l2nb is less than BUDMIN by performing a sanity check in the caller.
Return -EIO if the check fails.
Changes in v4: Thanks to Shaggy for the review. We now perform a sanity check instead of continuing as if nothing is wrong.
fs/jfs/jfs_dmap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 974ecf5e0d95..89c22a18314f 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -1217,7 +1217,7 @@ dbAllocNear(struct bmap * bmp,
int word, lword, rc;
s8 *leaf;

- if (dp->tree.leafidx != cpu_to_le32(LEAFIND)) {
+ if (dp->tree.leafidx != cpu_to_le32(LEAFIND) || l2nb >= L2DBWORD) {
jfs_error(bmp->db_ipbmap->i_sb, "Corrupt dmap page\n");
return -EIO;
}
@@ -1969,7 +1969,7 @@ dbAllocDmapLev(struct bmap * bmp,
if (dbFindLeaf((dmtree_t *) &dp->tree, l2nb, &leafidx, false))
return -ENOSPC;

- if (leafidx < 0)
+ if (leafidx < 0 || l2nb >= L2DBWORD)
return -EIO;

/* determine the block number within the file system corresponding
--
2.25.1

commit: 6c52d4da Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=116eb2a7980000
kernel config: https://syzkaller.appspot.com/x/.config?x=35698c25466f388c
patch: https://syzkaller.appspot.com/x/patch.diff?x=1293e6f7980000