From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-43408: ceph: add a bunch of missing ceph_path_info initializers
Date: Fri, 8 May 2026 16:22:17 +0200 [thread overview]
Message-ID: <2026050842-CVE-2026-43408-6f0a@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
ceph: add a bunch of missing ceph_path_info initializers
ceph_mdsc_build_path() must be called with a zero-initialized
ceph_path_info parameter, or else the following
ceph_mdsc_free_path_info() may crash.
Example crash (on Linux 6.18.12):
virt_to_cache: Object is not a Slab page!
WARNING: CPU: 184 PID: 2871736 at mm/slub.c:6732 kmem_cache_free+0x316/0x400
[...]
Call Trace:
[...]
ceph_open+0x13d/0x3e0
do_dentry_open+0x134/0x480
vfs_open+0x2a/0xe0
path_openat+0x9a3/0x1160
[...]
cache_from_obj: Wrong slab cache. names_cache but object is from ceph_inode_info
WARNING: CPU: 184 PID: 2871736 at mm/slub.c:6746 kmem_cache_free+0x2dd/0x400
[...]
kernel BUG at mm/slub.c:634!
Oops: invalid opcode: 0000 [#1] SMP NOPTI
RIP: 0010:__slab_free+0x1a4/0x350
Some of the ceph_mdsc_build_path() callers had initializers, but
others had not, even though they were all added by commit 15f519e9f883
("ceph: fix race condition validating r_parent before applying state").
The ones without initializer are suspectible to random crashes. (I can
imagine it could even be possible to exploit this bug to elevate
privileges.)
Unfortunately, these Ceph functions are undocumented and its semantics
can only be derived from the code. I see that ceph_mdsc_build_path()
initializes the structure only on success, but not on error.
Calling ceph_mdsc_free_path_info() after a failed
ceph_mdsc_build_path() call does not even make sense, but that's what
all callers do, and for it to be safe, the structure must be
zero-initialized. The least intrusive approach to fix this is
therefore to add initializers everywhere.
The Linux kernel CVE team has assigned CVE-2026-43408 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.12.48 with commit db378e6f83ec705c6091c65d482d555edc2b0a72 and fixed in 6.12.78 with commit 644b47f0574fd82aeb9d00317eca8d1f2a525c8c
Issue introduced in 6.17 with commit 15f519e9f883b316d86e2bb6b767a023aafd9d83 and fixed in 6.18.19 with commit 8be8911f590813e6f90bc6407ced1b23e50bc5da
Issue introduced in 6.17 with commit 15f519e9f883b316d86e2bb6b767a023aafd9d83 and fixed in 6.19.9 with commit 453df1f4535842bf17ff1885a225e153d7ee3374
Issue introduced in 6.17 with commit 15f519e9f883b316d86e2bb6b767a023aafd9d83 and fixed in 7.0 with commit 43323a5934b660afae687e8e4e95ac328615a5c4
Issue introduced in 6.16.8 with commit 2bfe45987eb346e299d9f763f9cd05f77011519f
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-2026-43408
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/ceph/debugfs.c
fs/ceph/dir.c
fs/ceph/file.c
fs/ceph/inode.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/644b47f0574fd82aeb9d00317eca8d1f2a525c8c
https://git.kernel.org/stable/c/8be8911f590813e6f90bc6407ced1b23e50bc5da
https://git.kernel.org/stable/c/453df1f4535842bf17ff1885a225e153d7ee3374
https://git.kernel.org/stable/c/43323a5934b660afae687e8e4e95ac328615a5c4
reply other threads:[~2026-05-08 14:24 UTC|newest]
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