| 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-2024-36027: btrfs: zoned: do not flag ZEROOUT on non-dirty extent buffer |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| btrfs: zoned: do not flag ZEROOUT on non-dirty extent buffer |
| |
| Btrfs clears the content of an extent buffer marked as |
| EXTENT_BUFFER_ZONED_ZEROOUT before the bio submission. This mechanism is |
| introduced to prevent a write hole of an extent buffer, which is once |
| allocated, marked dirty, but turns out unnecessary and cleaned up within |
| one transaction operation. |
| |
| Currently, btrfs_clear_buffer_dirty() marks the extent buffer as |
| EXTENT_BUFFER_ZONED_ZEROOUT, and skips the entry function. If this call |
| happens while the buffer is under IO (with the WRITEBACK flag set, |
| without the DIRTY flag), we can add the ZEROOUT flag and clear the |
| buffer's content just before a bio submission. As a result: |
| |
| 1) it can lead to adding faulty delayed reference item which leads to a |
| FS corrupted (EUCLEAN) error, and |
| |
| 2) it writes out cleared tree node on disk |
| |
| The former issue is previously discussed in [1]. The corruption happens |
| when it runs a delayed reference update. So, on-disk data is safe. |
| |
| [1] https://lore.kernel.org/linux-btrfs/3f4f2a0ff1a6c818050434288925bdcf3cd719e5.1709124777.git.naohiro.aota@wdc.com/ |
| |
| The latter one can reach on-disk data. But, as that node is already |
| processed by btrfs_clear_buffer_dirty(), that will be invalidated in the |
| next transaction commit anyway. So, the chance of hitting the corruption |
| is relatively small. |
| |
| Anyway, we should skip flagging ZEROOUT on a non-DIRTY extent buffer, to |
| keep the content under IO intact. |
| |
| The Linux kernel CVE team has assigned CVE-2024-36027 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.8 with commit aa6313e6ff2bfbf736a2739047bba355d8241584 and fixed in 6.8.8 with commit f4b994fccbb6f294c4b31a6ca0114b09f7245043 |
| Issue introduced in 6.8 with commit aa6313e6ff2bfbf736a2739047bba355d8241584 and fixed in 6.9 with commit 68879386180c0efd5a11e800b0525a01068c9457 |
| |
| 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-2024-36027 |
| 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/extent_io.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/f4b994fccbb6f294c4b31a6ca0114b09f7245043 |
| https://git.kernel.org/stable/c/68879386180c0efd5a11e800b0525a01068c9457 |
