CVE-2025-38172

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

erofs: avoid using multiple devices with different type

For multiple devices, both primary and extra devices should be the same type. erofs_init_device has already guaranteed that if the primary is a file-backed device, extra devices should also be regular files.

However, if the primary is a block device while the extra device is a file-backed device, erofs_init_device will get an ENOTBLK, which is not treated as an error in erofs_fc_get_tree, and that leads to an UAF:

erofs_fc_get_tree get_tree_bdev_flags(erofs_fc_fill_super) erofs_read_superblock erofs_init_device // sbi->dif0 is not inited yet, // return -ENOTBLK deactivate_locked_super free(sbi) if (err is -ENOTBLK) sbi->dif0.file = filp_open() // sbi UAF

So if -ENOTBLK is hitted in erofs_init_device, it means the primary device must be a block device, and the extra device is not a block device. The error can be converted to -EINVAL.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/65115472f741ca000d7ea4a5922214f93cd1516e
• https://git.kernel.org/stable/c/9748f2f54f66743ac77275c34886a9f890e18409
• https://git.kernel.org/stable/c/cd04beb9ce2773a16057248bb4fa424068ae3807