| 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-2024-27036: cifs: Fix writeback data corruption |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| cifs: Fix writeback data corruption |
| |
| cifs writeback doesn't correctly handle the case where |
| cifs_extend_writeback() hits a point where it is considering an additional |
| folio, but this would overrun the wsize - at which point it drops out of |
| the xarray scanning loop and calls xas_pause(). The problem is that |
| xas_pause() advances the loop counter - thereby skipping that page. |
| |
| What needs to happen is for xas_reset() to be called any time we decide we |
| don't want to process the page we're looking at, but rather send the |
| request we are building and start a new one. |
| |
| Fix this by copying and adapting the netfslib writepages code as a |
| temporary measure, with cifs writeback intending to be offloaded to |
| netfslib in the near future. |
| |
| This also fixes the issue with the use of filemap_get_folios_tag() causing |
| retry of a bunch of pages which the extender already dealt with. |
| |
| This can be tested by creating, say, a 64K file somewhere not on cifs |
| (otherwise copy-offload may get underfoot), mounting a cifs share with a |
| wsize of 64000, copying the file to it and then comparing the original file |
| and the copy: |
| |
| dd if=/dev/urandom of=/tmp/64K bs=64k count=1 |
| mount //192.168.6.1/test /mnt -o user=...,pass=...,wsize=64000 |
| cp /tmp/64K /mnt/64K |
| cmp /tmp/64K /mnt/64K |
| |
| Without the fix, the cmp fails at position 64000 (or shortly thereafter). |
| |
| The Linux kernel CVE team has assigned CVE-2024-27036 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.3 with commit d08089f649a0cfb2099c8551ac47eef0cc23fdf2 and fixed in 6.6.23 with commit e45deec35bf7f1f4f992a707b2d04a8c162f2240 |
| Issue introduced in 6.3 with commit d08089f649a0cfb2099c8551ac47eef0cc23fdf2 and fixed in 6.7.11 with commit 65f2ced695982ccd516196d0a9447d85dbe2eed5 |
| Issue introduced in 6.3 with commit d08089f649a0cfb2099c8551ac47eef0cc23fdf2 and fixed in 6.8.2 with commit 844b4e132f57f1333dc79feaa035075a096762e4 |
| Issue introduced in 6.3 with commit d08089f649a0cfb2099c8551ac47eef0cc23fdf2 and fixed in 6.9 with commit f3dc1bdb6b0b0693562c7c54a6c28bafa608ba3c |
| |
| 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-2024-27036 |
| 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/smb/client/file.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/e45deec35bf7f1f4f992a707b2d04a8c162f2240 |
| https://git.kernel.org/stable/c/65f2ced695982ccd516196d0a9447d85dbe2eed5 |
| https://git.kernel.org/stable/c/844b4e132f57f1333dc79feaa035075a096762e4 |
| https://git.kernel.org/stable/c/f3dc1bdb6b0b0693562c7c54a6c28bafa608ba3c |
