| 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-2024-56759: btrfs: fix use-after-free when COWing tree bock and tracing is enabled |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| btrfs: fix use-after-free when COWing tree bock and tracing is enabled |
| |
| When a COWing a tree block, at btrfs_cow_block(), and we have the |
| tracepoint trace_btrfs_cow_block() enabled and preemption is also enabled |
| (CONFIG_PREEMPT=y), we can trigger a use-after-free in the COWed extent |
| buffer while inside the tracepoint code. This is because in some paths |
| that call btrfs_cow_block(), such as btrfs_search_slot(), we are holding |
| the last reference on the extent buffer @buf so btrfs_force_cow_block() |
| drops the last reference on the @buf extent buffer when it calls |
| free_extent_buffer_stale(buf), which schedules the release of the extent |
| buffer with RCU. This means that if we are on a kernel with preemption, |
| the current task may be preempted before calling trace_btrfs_cow_block() |
| and the extent buffer already released by the time trace_btrfs_cow_block() |
| is called, resulting in a use-after-free. |
| |
| Fix this by moving the trace_btrfs_cow_block() from btrfs_cow_block() to |
| btrfs_force_cow_block() before the COWed extent buffer is freed. |
| This also has a side effect of invoking the tracepoint in the tree defrag |
| code, at defrag.c:btrfs_realloc_node(), since btrfs_force_cow_block() is |
| called there, but this is fine and it was actually missing there. |
| |
| The Linux kernel CVE team has assigned CVE-2024-56759 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 5.10.233 with commit ba5120a2fb5f23b4d39d302e181aa5d4e28a90d1 |
| Fixed in 5.15.176 with commit 526ff5b27f090fb15040471f892cd2c9899ce314 |
| Fixed in 6.1.124 with commit 66376f1a73cba57fd0af2631d7888605b738e499 |
| Fixed in 6.6.70 with commit 9a466b8693b9add05de99af00c7bdff8259ecf19 |
| Fixed in 6.12.8 with commit c3a403d8ce36f5a809a492581de5ad17843e4701 |
| Fixed in 6.13 with commit 44f52bbe96dfdbe4aca3818a2534520082a07040 |
| |
| 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-2024-56759 |
| 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/btrfs/ctree.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/ba5120a2fb5f23b4d39d302e181aa5d4e28a90d1 |
| https://git.kernel.org/stable/c/526ff5b27f090fb15040471f892cd2c9899ce314 |
| https://git.kernel.org/stable/c/66376f1a73cba57fd0af2631d7888605b738e499 |
| https://git.kernel.org/stable/c/9a466b8693b9add05de99af00c7bdff8259ecf19 |
| https://git.kernel.org/stable/c/c3a403d8ce36f5a809a492581de5ad17843e4701 |
| https://git.kernel.org/stable/c/44f52bbe96dfdbe4aca3818a2534520082a07040 |
