[PATCH] UBUNTU: SAUCE: LSM stacking: check for invalid zero sized writes

[Colin King]

From: Colin Ian King <colin.king at canonical.com>

BugLink: http://bugs.launchpad.net/bugs/1720779

Writing zero bytes to /proc/$pid/task/$pid/attr/context via
security_setprocattr cause an oops in memcpy_erms. Fix this by
checking for zero size and returning -EINVAL for this invalid
write size.

Detected by running stress-ng --procfs 0

Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 security/security.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/security/security.c b/security/security.c
index 31efa8c..cdc1627 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2007,6 +2007,9 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
 	char *temp;
 	char *cp;
 
+	if (!size)
+		return -EINVAL;
+
 	/*
 	 * If lsm is NULL look at all the modules to find one
 	 * that processes name. If lsm is not NULL only look at
-- 
2.7.4