[PATCH 3.16 076/254] 509: fix printing uninitialized stack memory when OID is empty

Ben Hutchings
2018-02-28T16:23:09Z

From: Eric Biggers <ebiggers3@gmail.com>

commit 8dfd2f22d3bf3ab7714f7495ad5d897b8845e8c1 upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
lib/oid_registry.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/lib/oid_registry.c
+++ b/lib/oid_registry.c
@@ -116,7 +116,7 @@ int sprint_oid(const void *data, size_t
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
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
}

return ret;
+
+bad:
+ snprintf(buffer, bufsize, "(bad)");
+ return -EBADMSG;
}
EXPORT_SYMBOL_GPL(sprint_oid);