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Fix locking and a double free in fsops rename and unlink #615

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Fix locking and a double free in fsops rename and unlink #615

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e379b4e
fix: releases of unheld meta_lock in rename and unlink error paths
matejk Jun 12, 2026
bbdf041
fix: double free of the new name on a late rename failure
matejk Jun 10, 2026
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41 changes: 28 additions & 13 deletions src/libltfs/ltfs_fsops.c
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Original file line number Diff line number Diff line change
Expand Up @@ -460,6 +460,13 @@ int ltfs_fsops_unlink(const char *path, ltfs_file_id *id, struct ltfs_volume *vo
}
parent = d->parent;

/* Acquire parent->meta_lock up front: the shared out: path releases it
* via fs_release_dentry_unlocked(), so every goto out (including the WORM
* and non-empty-directory error paths below) must hold it. Ordering is
* preserved: parent->contents_lock (held by fs_path_lookup) before
* parent->meta_lock before the child d->meta_lock. */
acquirewrite_mrsw(&parent->meta_lock);

if (parent->is_immutable || parent->is_appendonly) {
ltfsmsg(LTFS_ERR, 17237E, "unlink: parent is WORM");
ret = -LTFS_WORM_ENABLED;
Expand All @@ -482,7 +489,6 @@ int ltfs_fsops_unlink(const char *path, ltfs_file_id *id, struct ltfs_volume *vo
goto out;
}

acquirewrite_mrsw(&parent->meta_lock);
acquirewrite_mrsw(&d->meta_lock);

if (dcache_initialized(vol)) {
Expand Down Expand Up @@ -640,18 +646,9 @@ int ltfs_fsops_rename(const char *from, const char *to, ltfs_file_id *id, struct
goto out_release;
}

if (fromdir->is_appendonly || fromdir->is_immutable ) {
ltfsmsg(LTFS_ERR, 17237E, "rename: parent is WORM");
ret = -LTFS_WORM_ENABLED;
acquirewrite_mrsw(&fromdir->meta_lock);
goto out_release;
}
if (todir->is_immutable || todir->is_appendonly) {
ltfsmsg(LTFS_ERR, 17237E, "rename: target dir is WORM");
ret = -LTFS_WORM_ENABLED;
acquirewrite_mrsw(&fromdir->meta_lock);
goto out_release;
}
/* The WORM state of the source and target directories is checked below,
* after both directory meta_locks are held (the fields are meta_lock
* protected, and the out_release path expects both meta_locks held). */

/* Take locks in the appropriate order and look up the source and destination dentries */
if (todir == fromdir || fs_is_predecessor(todir, fromdir)) {
Expand Down Expand Up @@ -760,6 +757,20 @@ int ltfs_fsops_rename(const char *from, const char *to, ltfs_file_id *id, struct
}
#endif

/* Reject renames into or out of a WORM directory. Checked here, with both
* directory meta_locks held, rather than right after lookup: the fields are
* meta_lock protected and the out_unlock/out_release path releases both
* directory meta_locks via fs_release_dentry_unlocked. */
if (fromdir->is_immutable || fromdir->is_appendonly ||
todir->is_immutable || todir->is_appendonly) {
ltfsmsg(LTFS_ERR, 17237E, "rename: source or target dir is WORM");
ret = -LTFS_WORM_ENABLED;
fs_release_dentry(fromdentry);
if (todentry && todentry != fromdentry)
fs_release_dentry(todentry);
goto out_unlock;
}

if (fromdentry->is_immutable || fromdentry->is_appendonly) {
ltfsmsg(LTFS_ERR, 17237E, "rename: src entry is WORM");
ret = -LTFS_WORM_ENABLED;
Expand Down Expand Up @@ -857,6 +868,10 @@ int ltfs_fsops_rename(const char *from, const char *to, ltfs_file_id *id, struct
fromdentry->name.percent_encode = fs_is_percent_encode_required(fromdentry->name.name);
fromdentry->platform_safe_name = to_filename_copy2;
fromdentry->matches_name_criteria = index_criteria_match(fromdentry, vol);
/* Ownership of both buffers has moved to fromdentry; clear the locals so
* the out_free path does not free them again if a later step fails. */
to_filename_copy = NULL;
to_filename_copy2 = NULL;

/* Add fromdentry to new directory */
todir->child_list = fs_add_key_to_hash_table(todir->child_list, fromdentry, &ret);
Expand Down