[PATCH 5.15.y] jfs: fix null ptr deref in dtInsertEntry

[PATCH 5.15.y] jfs: fix null ptr deref in dtInsertEntry

[Aditya Dutt]

From: Edward Adam Davis <eadavis@qq.com>

[ Upstream commit ce6dede912f064a855acf6f04a04cbb2c25b8c8c ]

[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.

Closes: https://syzkaller.appspot.com/bug?extid=30b3e48dc48dd2ad45b6
Reported-by: syzbot+30b3e48dc48dd2ad45b6@syzkaller.appspotmail.com
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>
Signed-off-by: Aditya Dutt <duttaditya18@gmail.com>
---

I tested the patch manually using the C reproducer:
https://syzkaller.appspot.com/text?tag=ReproC&x=135c9b70580000
given in the syzkaller dashboard above.

 fs/jfs/jfs_dtree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
index 27ca98614b0b..cb57d4f1161f 100644
--- a/fs/jfs/jfs_dtree.c
+++ b/fs/jfs/jfs_dtree.c
@@ -835,6 +835,8 @@ 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
-- 
2.34.1

Re: [PATCH 5.15.y] jfs: fix null ptr deref in dtInsertEntry

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: ce6dede912f064a855acf6f04a04cbb2c25b8c8c

WARNING: Author mismatch between patch and upstream commit:
Backport author: Aditya Dutt<duttaditya18@gmail.com>
Commit author: Edward Adam Davis<eadavis@qq.com>

Status in newer kernel trees:
6.15.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (different SHA1: 6ea10dbb1e6c)
6.1.y | Present (different SHA1: 53023ab11836)

Note: The patch differs from the upstream commit:
---
1:  ce6dede912f06 ! 1:  13f964bdcd97f jfs: fix null ptr deref in dtInsertEntry
    @@ Metadata
      ## Commit message ##
         jfs: fix null ptr deref in dtInsertEntry
     
    +    [ Upstream commit ce6dede912f064a855acf6f04a04cbb2c25b8c8c ]
    +
         [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]
    @@ Commit message
         After got the page, check freelist first, if freelist == 0 then exit dtInsert()
         and return -EINVAL.
     
    +    Closes: https://syzkaller.appspot.com/bug?extid=30b3e48dc48dd2ad45b6
    +    Reported-by: syzbot+30b3e48dc48dd2ad45b6@syzkaller.appspotmail.com
         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>
    +    Signed-off-by: Aditya Dutt <duttaditya18@gmail.com>
     
      ## fs/jfs/jfs_dtree.c ##
     @@ fs/jfs/jfs_dtree.c: int dtInsert(tid_t tid, struct inode *ip,
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |