fstat(2) on file descriptors obtained via O_PATH is supported since
Linux 3.6. Fallback on older systems to lstat(2).
Fixes: 7e979b56 ("libselinux: restorecon: pin file to avoid TOCTOU issues")
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
libselinux/src/selinux_restorecon.c | 29 +++++++++++++++++++++++++----
1 file changed, 25 insertions(+), 4 deletions(-)
diff --git a/libselinux/src/selinux_restorecon.c b/libselinux/src/selinux_restorecon.c
index 9dd6be81..1a185ced 100644
--- a/libselinux/src/selinux_restorecon.c
+++ b/libselinux/src/selinux_restorecon.c
@@ -89,10 +89,22 @@ struct rest_flags {
bool count_errors;
};
+/* Linux version for availability tests. */
+static struct utsname uts;
+
static void restorecon_init(void)
{
struct selabel_handle *sehandle = NULL;
+ if (uname(&uts) < 0) {
+ /*
+ * utsname(2) should never fail, but assume oldest supported
+ * LTS release as backup
+ */
+ strncpy(uts.release, "4.9", sizeof(uts.release));
+ uts.release[sizeof(uts.release) - 1] = '\0';
+ }
+
if (!fc_sehandle) {
sehandle = selinux_restorecon_default_handle();
selinux_restorecon_set_sehandle(sehandle);
@@ -238,7 +250,6 @@ static uint64_t file_system_count(const char *name)
*/
static uint64_t exclude_non_seclabel_mounts(void)
{
- struct utsname uts;
FILE *fp;
size_t len;
int index = 0, found = 0;
@@ -247,7 +258,7 @@ static uint64_t exclude_non_seclabel_mounts(void)
char *buf = NULL, *item;
/* Check to see if the kernel supports seclabel */
- if (uname(&uts) == 0 && strverscmp(uts.release, "2.6.30") < 0)
+ if (strverscmp(uts.release, "2.6.30") < 0)
return 0;
if (is_selinux_enabled() <= 0)
return 0;
@@ -648,9 +659,19 @@ static int restorecon_sb(const char *pathname, struct rest_flags *flags, bool fi
if (fd < 0)
goto err;
+ /*
+ * fstat(2) on file descriptors obtained via O_PATH are supported
+ * since Linux 3.6, see man:open(2).
+ * Test fstat(2) first, support might have been backported.
+ */
rc = fstat(fd, &stat_buf);
- if (rc < 0)
- goto err;
+ if (rc < 0) {
+ if (errno == EBADF && strverscmp(uts.release, "3.6") < 0)
+ rc = lstat(pathname, &stat_buf);
+
+ if (rc < 0)
+ goto err;
+ }
if (rootpath != NULL && lookup_path[0] == '\0')
/* this is actually the root dir of the alt root. */
--
2.36.1
