CVE-2022-49707 ext4: add reserved GDT blocks check
A local attacker can cause a kernel crash by resizing a corrupted ext4 filesystem with specific feature flags, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-49707?
CVE-2022-49707 is a medium-severity vulnerability in Linux kernel, published on 26 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ext4: add reserved GDT blocks check
We capture a NULL pointer issue when resizing a corrupt ext4 image which is freshly clear resize_inode feature (not run e2fsck). It could be simply reproduced by following steps. The problem is because of the resize_inode feature was cleared, and it will convert the filesystem to meta_bg mode in ext4_resize_fs(), but the es->s_reserved_gdt_blocks was not reduced to zero, so could we mistakenly call reserve_backup_gdb() and passing an uninitialized resize_inode to it when adding new group descriptors.
mkfs.ext4 /dev/sda 3G tune2fs -O ^resize_inode /dev/sda #forget to run requested e2fsck mount /dev/sda /mnt resize2fs /dev/sda 8G
======== BUG: kernel NULL pointer dereference, address: 0000000000000028 CPU: 19 PID: 3243 Comm: resize2fs Not tainted 5.18.0-rc7-00001-gfde086c5ebfd #748 ... RIP: 0010:ext4_flex_group_add+0xe08/0x2570 ... Call Trace: <TASK> ext4_resize_fs+0xbec/0x1660 __ext4_ioctl+0x1749/0x24e0 ext4_ioctl+0x12/0x20 __x64_sys_ioctl+0xa6/0x110 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f2dd739617b ========
The fix is simple, add a check in ext4_resize_begin() to make sure that the es->s_reserved_gdt_blocks is zero when the resize_inode feature is disabled.
Weakness: CWE-476
Which versions are affected by CVE-2022-49707?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-49707?
Apply the vendor's patch.
Is CVE-2022-49707 being exploited?
There is no known exploitation of CVE-2022-49707 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-49707, GHSA-gcmg-mgh2-gvc3, UBUNTU-CVE-2022-49707.