Also a bug fix: disallow unrecognized branch modes at mount time, instead of
defaulting to "rw".
Signed-off-by: Erez Zadok <[email protected]>
---
fs/unionfs/main.c | 44 ++++++++++++++++++++++----------------------
fs/unionfs/super.c | 12 ++++++++----
fs/unionfs/union.h | 3 +--
3 files changed, 31 insertions(+), 28 deletions(-)
diff --git a/fs/unionfs/main.c b/fs/unionfs/main.c
index ffb0da1..22aa6e6 100644
--- a/fs/unionfs/main.c
+++ b/fs/unionfs/main.c
@@ -256,30 +256,21 @@ static int is_branch_overlap(struct dentry *dent1, struct dentry *dent2)
}
/*
- * Parse branch mode helper function
+ * Parse "ro" or "rw" options, but default to "rw" if no mode options was
+ * specified. Fill the mode bits in @perms. If encounter an unknown
+ * string, return -EINVAL. Otherwise return 0.
*/
-int __parse_branch_mode(const char *name)
+int parse_branch_mode(const char *name, int *perms)
{
- if (!name)
+ if (!name || !strcmp(name, "rw")) {
+ *perms = MAY_READ | MAY_WRITE;
return 0;
- if (!strcmp(name, "ro"))
- return MAY_READ;
- if (!strcmp(name, "rw"))
- return (MAY_READ | MAY_WRITE);
- return 0;
-}
-
-/*
- * Parse "ro" or "rw" options, but default to "rw" of no mode options
- * was specified.
- */
-int parse_branch_mode(const char *name)
-{
- int perms = __parse_branch_mode(name);
-
- if (perms == 0)
- perms = MAY_READ | MAY_WRITE;
- return perms;
+ }
+ if (!strcmp(name, "ro")) {
+ *perms = MAY_READ;
+ return 0;
+ }
+ return -EINVAL;
}
/*
@@ -350,8 +341,17 @@ static int parse_dirs_option(struct super_block *sb, struct unionfs_dentry_info
if (mode)
*mode++ = '\0';
- perms = parse_branch_mode(mode);
+ err = parse_branch_mode(mode, &perms);
+ if (err) {
+ printk(KERN_ERR "unionfs: invalid mode \"%s\" for "
+ "branch %d\n", mode, bindex);
+ goto out;
+ }
+ /* ensure that leftmost branch is writeable */
if (!bindex && !(perms & MAY_WRITE)) {
+ printk(KERN_ERR "unionfs: leftmost branch cannot be "
+ "read-only (use \"-o ro\" to create a "
+ "read-only union)\n");
err = -EINVAL;
goto out;
}
diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c
index 88f77d7..d9cf2a7 100644
--- a/fs/unionfs/super.c
+++ b/fs/unionfs/super.c
@@ -181,8 +181,8 @@ static noinline int do_remount_mode_option(char *optarg, int cur_branches,
goto out;
}
*modename++ = '\0';
- perms = __parse_branch_mode(modename);
- if (perms == 0) {
+ err = parse_branch_mode(modename, &perms);
+ if (err) {
printk(KERN_ERR "unionfs: invalid mode \"%s\" for \"%s\"\n",
modename, optarg);
goto out;
@@ -350,13 +350,17 @@ found_insertion_point:
modename = strchr(new_branch, '=');
if (modename)
*modename++ = '\0';
- perms = parse_branch_mode(modename);
-
if (!new_branch || !*new_branch) {
printk(KERN_ERR "unionfs: null new branch\n");
err = -EINVAL;
goto out;
}
+ err = parse_branch_mode(modename, &perms);
+ if (err) {
+ printk(KERN_ERR "unionfs: invalid mode \"%s\" for "
+ "branch \"%s\"\n", modename, new_branch);
+ goto out;
+ }
err = path_lookup(new_branch, LOOKUP_FOLLOW, &nd);
if (err) {
printk(KERN_ERR "unionfs: error accessing "
diff --git a/fs/unionfs/union.h b/fs/unionfs/union.h
index 283b085..20bff7b 100644
--- a/fs/unionfs/union.h
+++ b/fs/unionfs/union.h
@@ -474,8 +474,7 @@ static inline int is_robranch(const struct dentry *dentry)
*/
extern char *alloc_whname(const char *name, int len);
extern int check_branch(struct nameidata *nd);
-extern int __parse_branch_mode(const char *name);
-extern int parse_branch_mode(const char *name);
+extern int parse_branch_mode(const char *name, int *perms);
/*
* These two functions are here because it is kind of daft to copy and paste
--
1.5.2.2
--
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