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.

Affected Software

References

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