7

CVE-2021-47280

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

drm: Fix use-after-free read in drm_getunique()

There is a time-of-check-to-time-of-use error in drm_getunique() due
to retrieving file_priv->master prior to locking the device's master
mutex.

An example can be seen in the crash report of the use-after-free error
found by Syzbot:
https://syzkaller.appspot.com/bug?id=148d2f1dfac64af52ffd27b661981a540724f803

In the report, the master pointer was used after being freed. This is
because another process had acquired the device's master mutex in
drm_setmaster_ioctl(), then overwrote fpriv->master in
drm_new_set_master(). The old value of fpriv->master was subsequently
freed before the mutex was unlocked.

To fix this, we lock the device's master mutex before retrieving the
pointer from from fpriv->master. This patch passes the Syzbot
reproducer test.
Data is provided by the National Vulnerability Database (NVD)
Linux ≫ Linux Kernel Version < 4.14.237
Linux ≫ Linux Kernel Version >= 4.15 < 4.19.195
Linux ≫ Linux Kernel Version >= 4.20 < 5.4.126
Linux ≫ Linux Kernel Version >= 5.5 < 5.10.44
Linux ≫ Linux Kernel Version >= 5.11 < 5.12.11
Linux ≫ Linux Kernel Version5.13 Updaterc1
Linux ≫ Linux Kernel Version5.13 Updaterc2
Linux ≫ Linux Kernel Version5.13 Updaterc3
Linux ≫ Linux Kernel Version5.13 Updaterc4
Linux ≫ Linux Kernel Version5.13 Updaterc5
Zu dieser CVE wurde keine CISA KEV oder CERT.AT-Warnung gefunden.
EPSS Metriken
Type Source Score Percentile
EPSS FIRST.org 0.01% 0.016
CVSS Metriken
Source Base Score Exploit Score Impact Score Vector string
nvd@nist.gov 7 1 5.9
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state.

CWE-416 Use After Free

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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.