| 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-2024-46704: workqueue: Fix spruious data race in __flush_work() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| workqueue: Fix spruious data race in __flush_work() |
| |
| When flushing a work item for cancellation, __flush_work() knows that it |
| exclusively owns the work item through its PENDING bit. 134874e2eee9 |
| ("workqueue: Allow cancel_work_sync() and disable_work() from atomic |
| contexts on BH work items") added a read of @work->data to determine whether |
| to use busy wait for BH work items that are being canceled. While the read |
| is safe when @from_cancel, @work->data was read before testing @from_cancel |
| to simplify code structure: |
| |
| data = *work_data_bits(work); |
| if (from_cancel && |
| !WARN_ON_ONCE(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_BH)) { |
| |
| While the read data was never used if !@from_cancel, this could trigger |
| KCSAN data race detection spuriously: |
| |
| ================================================================== |
| BUG: KCSAN: data-race in __flush_work / __flush_work |
| |
| write to 0xffff8881223aa3e8 of 8 bytes by task 3998 on cpu 0: |
| instrument_write include/linux/instrumented.h:41 [inline] |
| ___set_bit include/asm-generic/bitops/instrumented-non-atomic.h:28 [inline] |
| insert_wq_barrier kernel/workqueue.c:3790 [inline] |
| start_flush_work kernel/workqueue.c:4142 [inline] |
| __flush_work+0x30b/0x570 kernel/workqueue.c:4178 |
| flush_work kernel/workqueue.c:4229 [inline] |
| ... |
| |
| read to 0xffff8881223aa3e8 of 8 bytes by task 50 on cpu 1: |
| __flush_work+0x42a/0x570 kernel/workqueue.c:4188 |
| flush_work kernel/workqueue.c:4229 [inline] |
| flush_delayed_work+0x66/0x70 kernel/workqueue.c:4251 |
| ... |
| |
| value changed: 0x0000000000400000 -> 0xffff88810006c00d |
| |
| Reorganize the code so that @from_cancel is tested before @work->data is |
| accessed. The only problem is triggering KCSAN detection spuriously. This |
| shouldn't need READ_ONCE() or other access qualifiers. |
| |
| No functional changes. |
| |
| The Linux kernel CVE team has assigned CVE-2024-46704 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.10 with commit 134874e2eee9380c2700411d4844cbc29297bc01 and fixed in 6.10.7 with commit 91d09642127a32fde231face2ff489af70eef316 |
| Issue introduced in 6.10 with commit 134874e2eee9380c2700411d4844cbc29297bc01 and fixed in 6.11 with commit 8bc35475ef1a23b0e224f3242eb11c76cab0ea88 |
| |
| 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-2024-46704 |
| 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: |
| kernel/workqueue.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/91d09642127a32fde231face2ff489af70eef316 |
| https://git.kernel.org/stable/c/8bc35475ef1a23b0e224f3242eb11c76cab0ea88 |
