jfs: fix null ptr deref in dtInsertEntry

[syzbot reported]
general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 5061 Comm: syz-executor404 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:dtInsertEntry+0xd0c/0x1780 fs/jfs/jfs_dtree.c:3713
...
[Analyze]
In dtInsertEntry(), when the pointer h has the same value as p, after writing
name in UniStrncpy_to_le(), p->header.flag will be cleared. This will cause the
previously true judgment "p->header.flag & BT-LEAF" to change to no after writing
the name operation, this leads to entering an incorrect branch and accessing the
uninitialized object ih when judging this condition for the second time.

[Fix]
After got the page, check freelist first, if freelist == 0 then exit dtInsert()
and return -EINVAL.

Reported-by: syzbot+bba84aef3a26fb93deb9@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>

diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
index 031d8f570f581f92f81eca48bf76062576d10cfd..5d3127ca68a42d76ac1d87b6ff6cee22d1b3b41d 100644 (file)
--- a/fs/jfs/jfs_dtree.c
+++ b/fs/jfs/jfs_dtree.c
@@ -834,6 +834,8 @@ int dtInsert(tid_t tid, struct inode *ip,
         * the full page.
         */
        DT_GETSEARCH(ip, btstack->top, bn, mp, p, index);
+       if (p->header.freelist == 0)
+               return -EINVAL;
 
        /*
         *      insert entry for new key