| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47125: sch_htb: fix refcount leak in htb_parent_to_leaf_offload |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| sch_htb: fix refcount leak in htb_parent_to_leaf_offload |
| |
| The commit ae81feb7338c ("sch_htb: fix null pointer dereference |
| on a null new_q") fixes a NULL pointer dereference bug, but it |
| is not correct. |
| |
| Because htb_graft_helper properly handles the case when new_q |
| is NULL, and after the previous patch by skipping this call |
| which creates an inconsistency : dev_queue->qdisc will still |
| point to the old qdisc, but cl->parent->leaf.q will point to |
| the new one (which will be noop_qdisc, because new_q was NULL). |
| The code is based on an assumption that these two pointers are |
| the same, so it can lead to refcount leaks. |
| |
| The correct fix is to add a NULL pointer check to protect |
| qdisc_refcount_inc inside htb_parent_to_leaf_offload. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47125 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.12 with commit ae81feb7338c89cee4e6aa0424bdab2ce2b52da2 and fixed in 5.12.10 with commit 2411c02d03892a5057499f8102d0cc1e0f852416 |
| Issue introduced in 5.12 with commit ae81feb7338c89cee4e6aa0424bdab2ce2b52da2 and fixed in 5.13 with commit 944d671d5faa0d78980a3da5c0f04960ef1ad893 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47125 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| net/sched/sch_htb.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/2411c02d03892a5057499f8102d0cc1e0f852416 |
| https://git.kernel.org/stable/c/944d671d5faa0d78980a3da5c0f04960ef1ad893 |
