kernel/git/stable/linux.git/fs/overlayfs, branch linux-rolling-stable

ovl: fix double end_creating() on the casefold-mismatch path

2026-09-07T15:36:30+00:00

commit 077ab8985ee278c3d8618182d335b0f0cd919e16 upstream. ovl_create_real() releases the new dentry twice when the casefold consistency check fails. The S_IFDIR branch calls end_creating() and sets err, then falls through to the common out: label which calls end_creating() on the same dentry again: case S_IFDIR: newdentry = ovl_do_mkdir(ofs, dir, newdentry, attr->mode); err = PTR_ERR_OR_ZERO(newdentry); if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) { pr_warn_ratelimited(...); end_creating(newdentry); /* first */ err = -EINVAL; } break; ... if (err) goto out; ... out: if (err) { end_creating(newdentry); /* second, same dentry */ return ERR_PTR(err); } end_creating() is end_dirop(), which does inode_unlock() on the parent and dput() on the dentry, so the parent directory's i_rwsem is unlocked twice and the dentry is put twice. The second unlock releases a lock that is not held, which is what wedges every later creation under that parent, and the second dput() drops a reference that was never taken. The branch was added by commit dfc7da402ccc ("ovl: Check for casefold consistency when creating new dentries") as a bare dput(), which already released the reference twice; commit fe497f0759e0 ("VFS: change vfs_mkdir() to unlock on failure.") converted both sites to end_creating(), adding the double unlock. This is reachable by an unprivileged user. The casefold consistency of the layers is validated at mount time in ovl_parse_layer(), and again on every lookup in ovl_lookup_single(), but ofs->workdir is the internal "work" subdirectory created inside the user-supplied workdir, and that subdirectory is not re-checked. Marking it casefolded after the mount therefore makes every ovl_create_temp() inherit the wrong state - and that path reaches ovl_create_real() through ovl_start_creating_temp(), which uses start_creating() with a generated name and so never runs the lookup-time check. unshare -Urm mount -t tmpfs -o casefold=utf8-12.1.0 tmpfs mnt mkdir -p mnt/lower/d mnt/upper mnt/work mnt/merged mount -t overlay ovl -o lowerdir=mnt/lower,\ upperdir=mnt/upper,workdir=mnt/work mnt/merged chattr +F mnt/work/work mkdir mnt/merged/d/sub # directory copy-up overlayfs: wrong inherited casefold (work/#5) and the next copy-up blocks forever on the parent's i_rwsem: mkdir D start_creating+0x65/0xb0 ovl_start_creating_temp+0xb0/0xe0 [overlay] ovl_create_temp+0xa3/0x1d0 [overlay] ovl_copy_up_one+0x1f1c/0x21c0 [overlay] ovl_copy_up_flags+0xf5/0x140 [overlay] ovl_create_object+0xb7/0x220 [overlay] ovl_mkdir+0x23/0x40 [overlay] Drop the end_creating() from the branch and let out: own the cleanup, which is what every other error path in this function already does. Fixes: dfc7da402ccc ("ovl: Check for casefold consistency when creating new dentries") Cc: stable@vger.kernel.org Signed-off-by: Vivek Parikh Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman

ovl: don't warn when the mount is completed from another user namespace

2026-08-10T07:35:54+00:00

fsopen() records the caller's user namespace in fc->user_ns and hands back an ordinary file descriptor. Nothing ties the task that calls fsconfig(FSCONFIG_CMD_CREATE) to the task that created the context. The fd is inherited across fork() and exec() and it can be passed over a unix socket. Completing a context from another user namespace is allowed on purpose. vfs_cmd_create() authorizes the create with mount_capable(), which for FS_USERNS_MOUNT checks ns_capable(fc->user_ns, CAP_SYS_ADMIN), and that succeeds for a task holding CAP_SYS_ADMIN in an ancestor of fc->user_ns. So an unprivileged task can reach the WARN_ON() in ovl_fill_super(): create a user and a mount namespace in a child, call fsopen("overlay") there, send the fscontext fd to the parent and let the parent issue FSCONFIG_CMD_CREATE. Both namespaces come from a plain unshare(1) and no capability is needed anywhere: WARNING: fs/overlayfs/super.c:1551 at ovl_fill_super+0x7b9/0x1e20 [overlay] CPU: 3 UID: 1000 PID: 3243376 Comm: fswarn Call Trace: get_tree_nodev+0x71/0xa0 ovl_get_tree+0x15/0x20 [overlay] vfs_get_tree+0x2a/0x100 vfs_cmd_create+0x60/0xf0 __do_sys_fsconfig+0x4b2/0x500 The child needs the mount namespace because fsopen() itself gates on may_mount(), which asks for CAP_SYS_ADMIN in the user namespace owning the caller's mount namespace. fsconfig() doesn't repeat that check. It is a WARN_ON() and not a WARN_ON_ONCE(), so the condition can be raised in a loop to taint the kernel and flood the log, and it panics a kernel booted with panic_on_warn. Keep refusing the mount and stop warning about it. ovl_parse_param() already spells a user namespace check this way for Opt_override_creds. Fixes: 1784fbc2ed9c ("ovl: port to new mount api") Cc: stable@vger.kernel.org # v6.5+ Link: https://patch.msgid.link/20260802-work-fill_super-warn-v1-1-4e987911a39a@kernel.org Reviewed-by: Jan Kara Signed-off-by: Christian Brauner (Amutable)

ovl: check access to copy_file_range source with src mounter creds

2026-07-22T14:42:28+00:00

Commit 5dae222a5ff0c ("vfs: allow copy_file_range to copy across devices") allowed filesystems that implement the copy_file_range() f_op to decide if they want to access cross-sb copy from/to the same fs type. The same commit added checks to verify same sb copy for filesystems that implement ->copy_file_range() and do not support cross-sb copy at the time, namely, to ceph, fuse and nfs. The two remaining fs which implement ->copy_file_range(), cifs and overlayfs started to support cross-sb copy from this time. While overlayfs does support cross-sb copy when the two underlying files are on the same base fs, the copy operation on the two real files from two different overalyfs filesystems is performed with the mounter creds of the destination overlayfs and the read permission access hook for the source file was called with the wrong creds. This could cause either deny of access to copy which would otherwise be allowed (e.g. with splice) or allow read access to file which would otherwise be denied. Fix the latter case by explicitly verifying read access to source file with the source overlayfs mounter creds. The former case remains a quirk of cross-sb overlayfs copy, but userspace could fall back to regular copy so no harm done. Fixes: 5dae222a5ff0c ("vfs: allow copy_file_range to copy across devices") Signed-off-by: Amir Goldstein Link: https://patch.msgid.link/20260712122421.203113-1-amir73il@gmail.com Signed-off-by: Christian Brauner (Amutable)

ovl: fix trusted xattr escape prefix matching

2026-07-22T11:48:00+00:00

In the trusted.* xattr namespace, ovl_is_escaped_xattr() compares one byte less than the escaped overlay xattr prefix length. This makes it match "trusted.overlay.overlay" without requiring the trailing dot. As a result, an xattr such as "trusted.overlay.overlayfoo" is incorrectly treated as an escaped overlay xattr. This can be reproduced by setting "trusted.overlay.overlayfoo" on a lower file and listing xattrs through an overlay mount. listxattr() then exposes it as "trusted.overlay.oo", and a following getxattr() on that listed name fails with ENODATA. Compare the full escaped prefix, including the trailing dot, so similarly-prefixed private xattrs are not misclassified. Fixes: dad02fad84cbc ("ovl: Support escaped overlay.* xattrs") Signed-off-by: Yichong Chen Link: https://patch.msgid.link/20260708082221.633602-1-chenyichong@uniontech.com Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner (Amutable)

ovl: fix comment about locking order

2026-07-01T13:26:25+00:00

Forgot to update the comment when we changed the locking order. Fixes: 162d06444070c ("ovl: reorder ovl_want_write() after ovl_inode_lock()") Signed-off-by: Amir Goldstein Link: https://patch.msgid.link/20260609184656.1916631-1-amir73il@gmail.com Signed-off-by: Christian Brauner (Amutable)

ovl: use linked upper dentry in copy-up tmpfile

2026-07-01T13:26:24+00:00

ovl_copy_up_tmpfile() stores the disconnected O_TMPFILE dentry as the overlay's upper dentry reference via ovl_inode_update(). vfs_tmpfile() allocated this dentry via d_alloc(parentpath->dentry, &slash_name), so d_name is "/" and d_parent is c->workdir. Local upper filesystems (ext4, btrfs, xfs, ...) immediately rename it to "#" via d_mark_tmpfile() inside their ->tmpfile() op; FUSE and virtiofs do not, so both fields stay that way. Neither identifies the destination directory and filename where ovl_do_link() actually linked the file. When the upper filesystem implements ->d_revalidate() (e.g. FUSE or virtiofs), ovl_revalidate_real() calls it with the dentry's parent inode and a snapshot of d_name. The server tries to look up "/" inside c->workdir, fails, and overlayfs reports -ESTALE. This causes persistent ESTALE errors for any file that was copied up via the tmpfile path, breaking dpkg, apt, and other tools that do rename-over-existing on overlayfs with a FUSE/virtiofs upper. Before commit 6b52243f633e ("ovl: fold copy-up helpers into callers"), the tmpfile copy-up path used a dedicated helper ovl_link_tmpfile() that captured the linked destination dentry returned by ovl_do_link(): err = ovl_do_link(temp, udir, upper); ... if (!err) *newdentry = dget(upper); and published it via ovl_inode_update(d_inode(c->dentry), newdentry). The fold inlined ovl_do_link() into ovl_copy_up_tmpfile() but dropped the dget(upper) capture, and rewrote the publish line as ovl_inode_update(d_inode(c->dentry), dget(temp)) — where temp is the disconnected O_TMPFILE dentry. Fix by keeping a reference to the linked destination dentry after ovl_do_link() succeeds, and publishing that dentry at the existing ovl_inode_update() call site. The non-tmpfile/workdir path continues to publish the renamed temporary dentry. Reproducer: - Mount overlayfs with virtiofs (or a FUSE fs whose server advertises FUSE_TMPFILE) as upper - Run: dpkg -i - Observe: "error installing new file '...': Stale file handle" Fixes: 6b52243f633e ("ovl: fold copy-up helpers into callers") Cc: stable@vger.kernel.org # v4.20+ Signed-off-by: Souvik Banerjee Link: https://patch.msgid.link/20260501232735.2610824-1-souvik@amlalabs.com Reviewed-by: Amir Goldstein Reviewed-by: Miklos Szeredi Signed-off-by: Christian Brauner (Amutable)

ovl: keep err zero after successful ovl_cache_get()

2026-05-18T12:56:15+00:00

ovl_iterate_merged() stores PTR_ERR(cache) in err before checking IS_ERR(cache). On success err holds the truncated cache pointer and can be returned as a bogus non-zero error. The syzbot reproducer reaches this through overlay-on-overlay readdir: getdents64 iterate_dir(outer overlay file) ovl_iterate_merged() ovl_cache_get() ovl_dir_read_merged() ovl_dir_read() iterate_dir(inner overlay file) ovl_iterate_merged() Only compute PTR_ERR(cache) on the error path. Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c Cc: stable@vger.kernel.org Signed-off-by: Nirmoy Das Link: https://patch.msgid.link/20260514144258.3068715-1-nirmoyd@nvidia.com Signed-off-by: Christian Brauner

ovl: fix verity lazy-load guard broken by fsverity_active() semantic change

2026-05-06T15:37:30+00:00

Commit f77f281b6118 ("fsverity: use a hashtable to find the fsverity_info") made fsverity_active() check whether the inode has the verity flag, rather than whether the inode's fsverity_info is loaded. This broke ovl_ensure_verity_loaded(), which wants to load the fsverity_info for any verity inodes that haven't had it loaded yet. Therefore, to check that the fsverity_info hasn't yet been loaded, use fsverity_get_info(inode) == NULL instead of !fsverity_active(inode). Also, since fsverity_get_info() now involves a hash table lookup, put the more lightweight IS_VERITY() flag check first. Fixes: f77f281b6118 ("fsverity: use a hashtable to find the fsverity_info") Cc: stable@vger.kernel.org Link: https://github.com/bootc-dev/bootc/issues/2174 Signed-off-by: Colin Walters Acked-by: Amir Goldstein Link: https://patch.msgid.link/20260505224257.23213-1-ebiggers@kernel.org Signed-off-by: Eric Biggers

Merge tag 'pull-dcache-busy-wait' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2026-04-21T14:30:44+00:00

Pull dcache busy loop updates from Al Viro: "Fix livelocks in shrink_dcache_tree() If shrink_dcache_tree() finds a dentry in the middle of being killed by another thread, it has to wait until the victim finishes dying, gets detached from the tree and ceases to pin its parent. The way we used to deal with that amounted to busy-wait; unfortunately, it's not just inefficient but can lead to reliably reproducible hard livelocks. Solved by having shrink_dentry_tree() attach a completion to such dentry, with dentry_unlist() calling complete() on all objects attached to it. With a bit of care it can be done without growing struct dentry or adding overhead in normal case" * tag 'pull-dcache-busy-wait' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: get rid of busy-waiting in shrink_dcache_tree() dcache.c: more idiomatic "positives are not allowed" sanity checks struct dentry: make ->d_u anonymous for_each_alias(): helper macro for iterating through dentries of given inode

Merge tag 'lsm-pr-20260410' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm

2026-04-13T22:17:28+00:00

Pull LSM updates from Paul Moore: "We only have five patches in the LSM tree, but three of the five are for an important bugfix relating to overlayfs and the mmap() and mprotect() access controls for LSMs. Highlights below: - Fix problems with the mmap() and mprotect() LSM hooks on overlayfs As we are dealing with problems both in mmap() and mprotect() there are essentially two components to this fix, spread across three patches with all marked for stable. The simplest portion of the fix is the creation of a new LSM hook, security_mmap_backing_file(), that is used to enforce LSM mmap() access controls on backing files in the stacked/overlayfs case. The existing security_mmap_file() does not have visibility past the user file. You can see from the associated SELinux hook callback the code is fairly straightforward. The mprotect() fix is a bit more complicated as there is no way in the mprotect() code path to inspect both the user and backing files, and bolting on a second file reference to vm_area_struct wasn't really an option. The solution taken here adds a LSM security blob and associated hooks to the backing_file struct that LSMs can use to capture and store relevant information from the user file. While the necessary SELinux information is relatively small, a single u32, I expect other LSMs to require more than that, and a dedicated backing_file LSM blob provides a storage mechanism without negatively impacting other filesystems. I want to note that other LSMs beyond SELinux have been involved in the discussion of the fixes presented here and they are working on their own related changes using these new hooks, but due to other issues those patches will be coming at a later date. - Use kstrdup_const()/kfree_const() for securityfs symlink targets - Resolve a handful of kernel-doc warnings in cred.h" * tag 'lsm-pr-20260410' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: selinux: fix overlayfs mmap() and mprotect() access checks lsm: add backing_file LSM hooks fs: prepare for adding LSM blob to backing_file securityfs: use kstrdup_const() to manage symlink targets cred: fix kernel-doc warnings in cred.h