From: Max Kellermann <max.kellermann@ionos.com> mainline inclusion from mainline-v7.0-rc4 commit 43323a5934b660afae687e8e4e95ac328615a5c4 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14967 CVE: CVE-2026-43408 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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. Cc: stable@vger.kernel.org Fixes: 15f519e9f883 ("ceph: fix race condition validating r_parent before applying state") Signed-off-by: Max Kellermann <max.kellermann@ionos.com> Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Conflicts: fs/ceph/debugfs.c fs/ceph/dir.c fs/ceph/file.c fs/ceph/inode.c [Context conflicts in fs/ceph/debugfs.c. For other files, struct ceph_path_info path_info are all properly initialized to {0}] Signed-off-by: Pan Taixi <pantaixi1@huawei.com> --- fs/ceph/debugfs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c index f00b333676d9..b44e44709e0a 100644 --- a/fs/ceph/debugfs.c +++ b/fs/ceph/debugfs.c @@ -79,7 +79,7 @@ static int mdsc_show(struct seq_file *s, void *p) if (req->r_inode) { seq_printf(s, " #%llx", ceph_ino(req->r_inode)); } else if (req->r_dentry) { - struct ceph_path_info path_info; + struct ceph_path_info path_info = {0}; path = ceph_mdsc_build_path(mdsc, req->r_dentry, &path_info, 0); if (IS_ERR(path)) @@ -99,7 +99,7 @@ static int mdsc_show(struct seq_file *s, void *p) } if (req->r_old_dentry) { - struct ceph_path_info path_info; + struct ceph_path_info path_info = {0}; path = ceph_mdsc_build_path(mdsc, req->r_old_dentry, &path_info, 0); if (IS_ERR(path)) -- 2.34.1