[PATCH] jfs: Fix array-index-out-of-bounds in diFree

[Jeongjun Park <aha310510@gmail.com>]

[syzbot report]
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_imap.c:886:2
index 524288 is out of range for type 'struct mutex[128]'
CPU: 0 PID: 113 Comm: jfsCommit Not tainted 6.9.0-rc5-syzkaller-00036-g9d1ddab261f3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429
 diFree+0x21c3/0x2fb0 fs/jfs/jfs_imap.c:886
 jfs_evict_inode+0x32d/0x440 fs/jfs/inode.c:156
 evict+0x2a8/0x630 fs/inode.c:667
 txUpdateMap+0x829/0x9f0 fs/jfs/jfs_txnmgr.c:2367
 txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline]
 jfs_lazycommit+0x49a/0xb80 fs/jfs/jfs_txnmgr.c:2733
 kthread+0x2f0/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
---[ end trace ]---
Kernel panic - not syncing: UBSAN: panic_on_warn set ...
CPU: 1 PID: 113 Comm: jfsCommit Not tainted 6.9.0-rc5-syzkaller-00036-g9d1ddab261f3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 panic+0x349/0x860 kernel/panic.c:348
 check_panic_on_warn+0x86/0xb0 kernel/panic.c:241
 ubsan_epilogue lib/ubsan.c:236 [inline]
 __ubsan_handle_out_of_bounds+0x141/0x150 lib/ubsan.c:429
 diFree+0x21c3/0x2fb0 fs/jfs/jfs_imap.c:886
 jfs_evict_inode+0x32d/0x440 fs/jfs/inode.c:156
 evict+0x2a8/0x630 fs/inode.c:667
 txUpdateMap+0x829/0x9f0 fs/jfs/jfs_txnmgr.c:2367
 txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline]
 jfs_lazycommit+0x49a/0xb80 fs/jfs/jfs_txnmgr.c:2733
 kthread+0x2f0/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Kernel Offset: disabled
Rebooting in 86400 seconds..
===========================================================

Due to overflow, a value that is too large is entered into the agno 
value. Therefore, we need to add code to check the agno value.

Reported-by: syzbot+241c815bda521982cb49@syzkaller.appspotmail.com
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
 fs/jfs/jfs_imap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index 2ec35889ad24..0aac083bc0db 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -881,6 +881,11 @@ int diFree(struct inode *ip)
 	 */
 	agno = BLKTOAG(JFS_IP(ip)->agstart, JFS_SBI(ip->i_sb));
 
+	if(agno >= MAXAG || agno < 0){
+		jfs_error(ip->i_sb, "invalid array index (0 <= agno < MAXAG), agno = %d\n", agno);
+		return -ENOMEM;
+	}
+
 	/* Lock the AG specific inode map information
 	 */
 	AG_LOCK(imap, agno);
-- 
2.34.1