| 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-2025-21654: ovl: support encoding fid from inode with no alias |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| ovl: support encoding fid from inode with no alias |
| |
| Dmitry Safonov reported that a WARN_ON() assertion can be trigered by |
| userspace when calling inotify_show_fdinfo() for an overlayfs watched |
| inode, whose dentry aliases were discarded with drop_caches. |
| |
| The WARN_ON() assertion in inotify_show_fdinfo() was removed, because |
| it is possible for encoding file handle to fail for other reason, but |
| the impact of failing to encode an overlayfs file handle goes beyond |
| this assertion. |
| |
| As shown in the LTP test case mentioned in the link below, failure to |
| encode an overlayfs file handle from a non-aliased inode also leads to |
| failure to report an fid with FAN_DELETE_SELF fanotify events. |
| |
| As Dmitry notes in his analyzis of the problem, ovl_encode_fh() fails |
| if it cannot find an alias for the inode, but this failure can be fixed. |
| ovl_encode_fh() seldom uses the alias and in the case of non-decodable |
| file handles, as is often the case with fanotify fid info, |
| ovl_encode_fh() never needs to use the alias to encode a file handle. |
| |
| Defer finding an alias until it is actually needed so ovl_encode_fh() |
| will not fail in the common case of FAN_DELETE_SELF fanotify events. |
| |
| The Linux kernel CVE team has assigned CVE-2025-21654 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.6 with commit 16aac5ad1fa94894b798dd522c5c3a6a0628d7f0 and fixed in 6.6.74 with commit f0c0ac84de17c37e6e84da65fb920f91dada55ad |
| Issue introduced in 6.6 with commit 16aac5ad1fa94894b798dd522c5c3a6a0628d7f0 and fixed in 6.12.10 with commit 3c7c90274ae339e1ad443c9be1c67a20b80b9c76 |
| Issue introduced in 6.6 with commit 16aac5ad1fa94894b798dd522c5c3a6a0628d7f0 and fixed in 6.13 with commit c45beebfde34aa71afbc48b2c54cdda623515037 |
| |
| 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-2025-21654 |
| 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/overlayfs/export.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/f0c0ac84de17c37e6e84da65fb920f91dada55ad |
| https://git.kernel.org/stable/c/3c7c90274ae339e1ad443c9be1c67a20b80b9c76 |
| https://git.kernel.org/stable/c/c45beebfde34aa71afbc48b2c54cdda623515037 |
