| 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-2023-52786: ext4: fix racy may inline data check in dio write |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| ext4: fix racy may inline data check in dio write |
| |
| syzbot reports that the following warning from ext4_iomap_begin() |
| triggers as of the commit referenced below: |
| |
| if (WARN_ON_ONCE(ext4_has_inline_data(inode))) |
| return -ERANGE; |
| |
| This occurs during a dio write, which is never expected to encounter |
| an inode with inline data. To enforce this behavior, |
| ext4_dio_write_iter() checks the current inline state of the inode |
| and clears the MAY_INLINE_DATA state flag to either fall back to |
| buffered writes, or enforce that any other writers in progress on |
| the inode are not allowed to create inline data. |
| |
| The problem is that the check for existing inline data and the state |
| flag can span a lock cycle. For example, if the ilock is originally |
| locked shared and subsequently upgraded to exclusive, another writer |
| may have reacquired the lock and created inline data before the dio |
| write task acquires the lock and proceeds. |
| |
| The commit referenced below loosens the lock requirements to allow |
| some forms of unaligned dio writes to occur under shared lock, but |
| AFAICT the inline data check was technically already racy for any |
| dio write that would have involved a lock cycle. Regardless, lift |
| clearing of the state bit to the same lock critical section that |
| checks for preexisting inline data on the inode to close the race. |
| |
| The Linux kernel CVE team has assigned CVE-2023-52786 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.5 with commit 310ee0902b8d9d0a13a5a13e94688a5863fa29c2 and fixed in 6.5.13 with commit e3b83d87c93eb6fc96a80b5e8527f7dc9f5a11bc |
| Issue introduced in 6.5 with commit 310ee0902b8d9d0a13a5a13e94688a5863fa29c2 and fixed in 6.6.3 with commit 7343c23ebcadbedc23a7063d1e24d976eccb0d0d |
| Issue introduced in 6.5 with commit 310ee0902b8d9d0a13a5a13e94688a5863fa29c2 and fixed in 6.7 with commit ce56d21355cd6f6937aca32f1f44ca749d1e4808 |
| |
| 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-2023-52786 |
| 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/ext4/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/e3b83d87c93eb6fc96a80b5e8527f7dc9f5a11bc |
| https://git.kernel.org/stable/c/7343c23ebcadbedc23a7063d1e24d976eccb0d0d |
| https://git.kernel.org/stable/c/ce56d21355cd6f6937aca32f1f44ca749d1e4808 |
