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.