[PATCH] FS:JFS:UBSAN:array-index-out-of-bounds in dbAdjTree

[Osama Muhammad <osmtendev@gmail.com>]

Syzkaller reported the following issue:

UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dmap.c:2867:6
index 196694 is out of range for type 's8[1365]' (aka 'signed char[1365]')
CPU: 1 PID: 109 Comm: jfsCommit Not tainted 6.6.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 ubsan_epilogue lib/ubsan.c:217 [inline]
 __ubsan_handle_out_of_bounds+0x11c/0x150 lib/ubsan.c:348
 dbAdjTree+0x474/0x4f0 fs/jfs/jfs_dmap.c:2867
 dbJoin+0x210/0x2d0 fs/jfs/jfs_dmap.c:2834
 dbFreeBits+0x4eb/0xda0 fs/jfs/jfs_dmap.c:2331
 dbFreeDmap fs/jfs/jfs_dmap.c:2080 [inline]
 dbFree+0x343/0x650 fs/jfs/jfs_dmap.c:402
 txFreeMap+0x798/0xd50 fs/jfs/jfs_txnmgr.c:2534
 txUpdateMap+0x342/0x9e0
 txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline]
 jfs_lazycommit+0x47a/0xb70 fs/jfs/jfs_txnmgr.c:2732
 kthread+0x2d3/0x370 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
 </TASK>
================================================================================
Kernel panic - not syncing: UBSAN: panic_on_warn set ...
CPU: 1 PID: 109 Comm: jfsCommit Not tainted 6.6.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 panic+0x30f/0x770 kernel/panic.c:340
 check_panic_on_warn+0x82/0xa0 kernel/panic.c:236
 ubsan_epilogue lib/ubsan.c:223 [inline]
 __ubsan_handle_out_of_bounds+0x13c/0x150 lib/ubsan.c:348
 dbAdjTree+0x474/0x4f0 fs/jfs/jfs_dmap.c:2867
 dbJoin+0x210/0x2d0 fs/jfs/jfs_dmap.c:2834
 dbFreeBits+0x4eb/0xda0 fs/jfs/jfs_dmap.c:2331
 dbFreeDmap fs/jfs/jfs_dmap.c:2080 [inline]
 dbFree+0x343/0x650 fs/jfs/jfs_dmap.c:402
 txFreeMap+0x798/0xd50 fs/jfs/jfs_txnmgr.c:2534
 txUpdateMap+0x342/0x9e0
 txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline]
 jfs_lazycommit+0x47a/0xb70 fs/jfs/jfs_txnmgr.c:2732
 kthread+0x2d3/0x370 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
 </TASK>
Kernel Offset: disabled
Rebooting in 86400 seconds..

The issue is caused when the value of lp becomes greater than
CTLTREESIZE which is the max size of stree. Adding a simple check
solves this issue. I was not sure about error return as a function
does not return. If there is something needed in that regard please
do point out.

The patch is tested via syzbot.

Reported-by: syzbot+39ba34a099ac2e9bd3cb@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=39ba34a099ac2e9bd3cb
Signed-off-by: Osama Muhammad <osmtendev@gmail.com>
---
 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 a3eb1e826947..decb3be66a86 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2854,6 +2854,9 @@ static void dbAdjTree(dmtree_t * tp, int leafno, int newval)
 	/* is the current value the same as the old value ?  if so,
 	 * there is nothing to do.
 	 */
+	if (lp >= CTLTREESIZE)
+		return;
+
 	if (tp->dmt_stree[lp] == newval)
 		return;
 
-- 
2.34.1