CVE-2024-44939

In the Linux kernel, the following vulnerability has been resolved:

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.

Weakness

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/53023ab11836ac56fd75f7a71ec1356e50920fa9
• https://git.kernel.org/stable/c/6ea10dbb1e6c58384136e9adfd75f81951e423f6
• https://git.kernel.org/stable/c/9c2ac38530d1a3ee558834dfa16c85a40fd0e702
• https://git.kernel.org/stable/c/ce6dede912f064a855acf6f04a04cbb2c25b8c8c