Hi David, On Tue, Nov 28, 2017 at 11:03:54AM +0000, David Howells wrote: > I wonder if all -EBADMSG returns here should just print "(badoid)" into the > buffer. > I don't really care either way; it's just a question of whether it's better to truncate the bad part, or print a special value. If you prefer the latter here is a revised patch to consider. (I went with "(bad)" instead of "(badoid)" because the callers already label the string as an OID.): ---8<--- >From 5a68ec1afd819e145446a97268bd790f9f3226b3 Mon Sep 17 00:00:00 2001 From: Eric Biggers <ebiggers@xxxxxxxxxx> Date: Tue, 28 Nov 2017 10:47:42 -0800 Subject: [PATCH v2] X.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@xxxxxxxxxx> --- 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); -- 2.15.0.417.g466bffb3ac-goog