Description
In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class handling This patch fixes a Use-After-Free vulnerability in the HFSC qdisc class handling. The issue occurs due to a time-of-check/time-of-use condition in hfsc_change_class() when working with certain child qdiscs like netem or codel. The vulnerability works as follows: 1. hfsc_change_class() checks if a class has packets (q.qlen != 0) 2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g., codel, netem) might drop packets and empty the queue 3. The code continues assuming the queue is still non-empty, adding the class to vttree 4. This breaks HFSC scheduler assumptions that only non-empty classes are in vttree 5. Later, when the class is destroyed, this can lead to a Use-After-Free The fix adds a second queue length check after qdisc_peek_len() to verify the queue wasn't emptied.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 to < 28b09a067831f7317c3841812276022d6c940677affected21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 to < 39b9095dd3b55d9b2743df038c32138efa34a9deaffected21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 to < fcc8ede663569c704fb00a702973bd6c00373283affected21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 to < 20d584a33e480ae80d105f43e0e7b56784da41b9affected21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 to < 3aa852e3605000d5c47035c3fc3a986d14ccfa9faffected21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 to < 86cd4641c713455a4f1c8e54c370c598c2b1cee0affected21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 to < bb583c88d23b72d8d16453d24856c99bd93dadf5affected21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 to < 3df275ef0a6ae181e8428a6589ef5d5231e58b5caffected
Linux Linux
Default version status: affected
4.14affected0 to < 4.14unaffected5.4.293 to ≤ 5.4.*unaffected5.10.237 to ≤ 5.10.*unaffected5.15.181 to ≤ 5.15.*unaffected6.1.136 to ≤ 6.1.*unaffected6.6.89 to ≤ 6.6.*unaffected6.12.26 to ≤ 6.12.*unaffected6.14.5 to ≤ 6.14.*unaffected6.15 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677 ↗
- https://git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de ↗
- https://git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283 ↗
- https://git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9 ↗
- https://git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f ↗
- https://git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0 ↗
- https://git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5 ↗
- https://git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c ↗
- https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html ↗
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html ↗