fabrics: Do not overflow when reading systemd_uuid

gcc complains with:

../src/nvme/fabrics.c:774:15: warning: ‘read’ writing 512 bytes into a region of size 37 overflows the destination [-Wstringop-overflow=]
  774 |         len = read(f, system_uuid, 512);
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~
../src/nvme/fabrics.c: In function ‘nvmf_hostnqn_generate’:
../src/nvme/fabrics.c:863:14: note: destination object ‘uuid_str’ of size 37
  863 |         char uuid_str[37]; /* e.g. 1b4e28ba-2fa1-11d2-883f-0016d3cca427 + \0 */
      |              ^~~~~~~~

Let's limit the read to 37 as we know that's the max size for a UUID.

Signed-off-by: Daniel Wagner <dwagner@suse.de>

diff --git a/src/nvme/fabrics.c b/src/nvme/fabrics.c
index 16e014027ce5387d2f2dcba326ea95db4e4946fd..3ab93210ed6b80d500fa912e3443138b9566cc3a 100644 (file)
--- a/src/nvme/fabrics.c
+++ b/src/nvme/fabrics.c
@@ -40,6 +40,7 @@
 #include "private.h"
 
 #define NVMF_HOSTID_SIZE       37
+#define UUID_SIZE              37  /* 1b4e28ba-2fa1-11d2-883f-0016d3cca427 + \0 */
 
 const char *nvmf_dev = "/dev/nvme-fabrics";
 const char *nvmf_hostnqn_file = "/etc/nvme/hostnqn";
@@ -771,7 +772,9 @@ static int uuid_from_device_tree(char *system_uuid)
        f = open(PATH_UUID_IBM, O_RDONLY);
        if (f < 0)
                return -ENXIO;
-       len = read(f, system_uuid, 512);
+
+       memset(system_uuid, 0, UUID_SIZE);
+       len = read(f, system_uuid, UUID_SIZE - 1);
        close(f);
        if (len < 0)
                return -ENXIO;
@@ -860,7 +863,7 @@ char *nvmf_hostnqn_generate()
 {
        char *hostnqn;
        int ret;
-       char uuid_str[37]; /* e.g. 1b4e28ba-2fa1-11d2-883f-0016d3cca427 + \0 */
+       char uuid_str[UUID_SIZE];
 #ifdef CONFIG_LIBUUID
        uuid_t uuid;
 #endif