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:

erofsfcgettree gettreebdevflags(erofsfcfillsuper) erofsreadsuperblock erofsinitdevice // sbi->dif0 is not inited yet, // return -ENOTBLK deactivatelockedsuper free(sbi) if (err is -ENOTBLK) sbi->dif0.file = filpopen() // 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.