linux-kernel - [PATCH AUTOSEL for 4.14 070/100] 509: fix printing uninitialized stack memory when OID is empty

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Message-ID: <20180128222547.7398-70-alexander.levin@microsoft.com>
Date:   Sun, 28 Jan 2018 22:26:44 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Eric Biggers <ebiggers3@...il.com>,
        Eric Biggers <ebiggers@...gle.com>,
        David Howells <dhowells@...hat.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.14 070/100] 509: fix printing uninitialized
 stack memory when OID is empty

From: Eric Biggers <ebiggers3@...il.com>

[ Upstream commit 8dfd2f22d3bf3ab7714f7495ad5d897b8845e8c1 ]

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: Sasha Levin <alexander.levin@...rosoft.com>
---
 lib/oid_registry.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/oid_registry.c b/lib/oid_registry.c
index 41b9e50711a7..b5f7d9986be1 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);
 
-- 
2.11.0