509: fix printing uninitialized stack memory when OID is empty

Callers of sprint_oid() do not check its return value before printing
the result.  In the case where the OID is zero-length, -EBADMSG was
being returned without anything being written to the buffer, resulting
in uninitialized stack memory being printed.  Fix this by writing
"(bad)" to the buffer in the cases where -EBADMSG is returned.

Fixes: 4f73175d0375 ("X.509: Add utility functions to render OIDs as strings")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/oid_registry.c b/lib/oid_registry.c
index 5a75d127995d..0bcac6ccb1b2 100644
--- a/lib/oid_registry.c
+++ b/lib/oid_registry.c
@@ -116,7 +116,7 @@ int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize)
         int count;
 
         if (v >= end)
-                return -EBADMSG;
+                goto bad;
 
         n = *v++;
         ret = count = snprintf(buffer, bufsize, "%u.%u", n / 40, n % 40);
@@ -134,7 +134,7 @@ int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize)
                         num = n & 0x7f;
                         do {
                                 if (v >= end)
-                                        return -EBADMSG;
+                                        goto bad;
                                 n = *v++;
                                 num <<= 7;
                                 num |= n & 0x7f;
@@ -148,6 +148,10 @@ int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize)
         }
 
         return ret;
+
+bad:
+        snprintf(buffer, bufsize, "(bad)");
+        return -EBADMSG;
 }
 EXPORT_SYMBOL_GPL(sprint_oid);