CVE-2022-49707 Information

Mar 01, 2025 cve

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: 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.

Reference

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