Bugzilla – Bug 1220622
VUL-0: CVE-2021-46993: kernel: sched: out-of-bound access in uclamp
Last modified: 2024-05-29 12:32:11 UTC
In the Linux kernel, the following vulnerability has been resolved: sched: Fix out-of-bound access in uclamp Util-clamp places tasks in different buckets based on their clamp values for performance reasons. However, the size of buckets is currently computed using a rounding division, which can lead to an off-by-one error in some configurations. For instance, with 20 buckets, the bucket size will be 1024/20=51. A task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly, correct indexes are in range [0,19], hence leading to an out of bound memory access. Clamp the bucket id to fix the issue. References: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-46993 https://www.cve.org/CVERecord?id=CVE-2021-46993 https://git.kernel.org/stable/c/3da3f804b82a0a382d523a21acf4cf3bb35f936d https://git.kernel.org/stable/c/42ee47c7e3569d9a0e2cb5053c496d97d380472f https://git.kernel.org/stable/c/687f523c134b7f0bd040ee1230f6d17990d54172 https://git.kernel.org/stable/c/6d2f8909a5fabb73fe2a63918117943986c39b6c https://git.kernel.org/stable/c/f7347c85490b92dd144fa1fba9e1eca501656ab3
cve/linux-5.3 is affected. Already fixed in cve/linux-5.14 and newer.
The out-of-bounds access only occurs if the CONFIG_UCLAMP_TASK scheduler feature is enabled. We do not enable this feature so the fix does not need to be applied.
(In reply to Roy Hopkins from comment #3) > The out-of-bounds access only occurs if the CONFIG_UCLAMP_TASK scheduler > feature is enabled. We do not enable this feature so the fix does not need > to be applied. Thanks for checking, I've updated the tracking.
All done, closing.