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

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Message-ID: <lsq.1519831218.244210866@decadent.org.uk>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Eric Biggers" <ebiggers@...gle.com>,
        "Eric Biggers" <ebiggers3@...il.com>,
        "David Howells" <dhowells@...hat.com>
Subject: [PATCH 3.16 076/254] 509: fix printing uninitialized stack memory
 when OID is empty

3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers3@...il.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@...gle.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.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);