Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
smack: fix cred UAF in smack_file_send_sigiotask()
When inspecting the credentials of another task, objective credentials (->real_cred, accessed with __task_cred()) must always be used.
Accessing ->cred on a non-current task is forbidden unless that task is being created or destroyed; a task is allowed to change its own ->cred pointer with no synchronization, and changing ->cred should only affect the current syscall.
smack_file_send_sigiotask() was accessing both sets of credentials: First tsk->cred, then __task_cred(tsk).
Fix it, always access the objective credentials here.
I have tested that this bug can lead to a KASAN-reported UAF of struct cred in smack_file_send_sigiotask(), and that this fix prevents the race.
Details
- Affected product:
- Debian 10 ELS , Debian 11 ELS , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
- Affected packages:
- linux @ 5.10.259 (+4 more)