CVE-2021-46937

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

mm/damon/dbgfs: fix struct pid leaks in dbgfs_target_ids_write()

DAMON debugfs interface increases the reference counts of struct pids for targets from the target_ids file write callback (dbgfs_target_ids_write()), but decreases the counts only in DAMON monitoring termination callback (dbgfs_before_terminate()).

Therefore, when target_ids file is repeatedly written without DAMON monitoring start/termination, the reference count is not decreased and therefore memory for the struct pid cannot be freed. This commit fixes this issue by decreasing the reference counts when target_ids is written.

Weakness

The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.

Affected Software

Extended Description

Resources such as files and directories may be inadvertently exposed through mechanisms such as insecure permissions, or when a program accidentally operates on the wrong object. For example, a program may intend that private files can only be provided to a specific user. This effectively defines a control sphere that is intended to prevent attackers from accessing these private files. If the file permissions are insecure, then parties other than the user will be able to access those files. A separate control sphere might effectively require that the user can only access the private files, but not any other files on the system. If the program does not ensure that the user is only requesting private files, then the user might be able to access other files on the system. In either case, the end result is that a resource has been exposed to the wrong party.

References

• https://git.kernel.org/stable/c/ebb3f994dd92f8fb4d70c7541091216c1e10cb71
• https://git.kernel.org/stable/c/ffe4a1ba1a82c416a6b3a09d46594f6a885ae141