[nfs-utils PATCH] mountd: fix is_subdirectory to understand '/'

[NeilBrown <neilb@suse.de>]

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The is_subdirectory() function checks if a given 'child' is a subdirectory
of the given 'parent'.
However it always fails if 'parent' == "/"  (because 'child' doesn't begin
with 'parent' followed by "/").

So change is_subdirectory() to special-case "/".

subexport() also tests if one directory is a subdirectory of the
other, and contains the same bug.  So change it to use is_subdirectory().

Finally, move is_subdirectory() and related path_matches() and
export_matches() earlier in the file to avoid a forward-reference.

This patch fixes a bug wherein if you export "/" with 'crossmnt', the
crossmnt flag is ineffective and you can only access the root
filesystem, not any descendants.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
index 3853bb6..45012be 100644
--- a/utils/mountd/cache.c
+++ b/utils/mountd/cache.c
@@ -343,6 +343,30 @@ static char *next_mnt(void **v, char *p)
 	return me->mnt_dir;
 }
 
+static int is_subdirectory(char *child, char *parent)
+{
+	size_t l = strlen(parent);
+
+	if (strcmp(parent, "/") == 0)
+		return 1;
+
+	return strcmp(child, parent) == 0
+		|| (strncmp(child, parent, l) == 0 && child[l] == '/');
+}
+
+static int path_matches(nfs_export *exp, char *path)
+{
+	if (exp->m_export.e_flags & NFSEXP_CROSSMOUNT)
+		return is_subdirectory(path, exp->m_export.e_path);
+	return strcmp(path, exp->m_export.e_path) == 0;
+}
+
+static int
+export_matches(nfs_export *exp, char *dom, char *path, struct addrinfo *ai)
+{
+	return path_matches(exp, path) && client_matches(exp, dom, ai);
+}
+
 /* True iff e1 is a child of e2 and e2 has crossmnt set: */
 static bool subexport(struct exportent *e1, struct exportent *e2)
 {
@@ -350,8 +374,7 @@ static bool subexport(struct exportent *e1, struct exportent *e2)
 	size_t l2 = strlen(p2);
 
 	return e2->e_flags & NFSEXP_CROSSMOUNT
-	       && strncmp(p1, p2, l2) == 0
-	       && p1[l2] == '/';
+		&& is_subdirectory(p1, p2);
 }
 
 struct parsed_fsid {
@@ -752,27 +775,6 @@ static int dump_to_cache(FILE *f, char *domain, char *path, struct exportent *ex
 	return qword_eol(f);
 }
 
-static int is_subdirectory(char *child, char *parent)
-{
-	size_t l = strlen(parent);
-
-	return strcmp(child, parent) == 0
-		|| (strncmp(child, parent, l) == 0 && child[l] == '/');
-}
-
-static int path_matches(nfs_export *exp, char *path)
-{
-	if (exp->m_export.e_flags & NFSEXP_CROSSMOUNT)
-		return is_subdirectory(path, exp->m_export.e_path);
-	return strcmp(path, exp->m_export.e_path) == 0;
-}
-
-static int
-export_matches(nfs_export *exp, char *dom, char *path, struct addrinfo *ai)
-{
-	return path_matches(exp, path) && client_matches(exp, dom, ai);
-}
-
 static nfs_export *
 lookup_export(char *dom, char *path, struct addrinfo *ai)
 {

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