| 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-2021-47577: io-wq: check for wq exit after adding new worker task_work |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| io-wq: check for wq exit after adding new worker task_work |
| |
| We check IO_WQ_BIT_EXIT before attempting to create a new worker, and |
| wq exit cancels pending work if we have any. But it's possible to have |
| a race between the two, where creation checks exit finding it not set, |
| but we're in the process of exiting. The exit side will cancel pending |
| creation task_work, but there's a gap where we add task_work after we've |
| canceled existing creations at exit time. |
| |
| Fix this by checking the EXIT bit post adding the creation task_work. |
| If it's set, run the same cancelation that exit does. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47577 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 5.15.11 with commit 4b4e5bbf9386d4ec21d91c0cb0fd60b9bba778ec |
| Fixed in 5.16 with commit 71a85387546e50b1a37b0fa45dadcae3bfb35cf6 |
| |
| 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-2021-47577 |
| 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: |
| fs/io-wq.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/4b4e5bbf9386d4ec21d91c0cb0fd60b9bba778ec |
| https://git.kernel.org/stable/c/71a85387546e50b1a37b0fa45dadcae3bfb35cf6 |
