[PATCH 2/4] asm-generic: uaccess: add missing access_ok() check to strnlen_user()

From: Mike Frysinger
Date: Sun Jun 14 2009 - 02:00:41 EST

The strnlen_user() function was missing a access_ok() check on the pointer
given. We've had cases on Blackfin systems where test programs caused
kernel crashes here because userspace passed up a NULL/-1 pointer and the
kernel gladly attempted to run strlen() on it.

Signed-off-by: Mike Frysinger <vapier@xxxxxxxxxx>
include/asm-generic/uaccess.h | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index cf3cb73..d299557 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -296,6 +296,8 @@ strncpy_from_user(char *dst, const char __user *src, long count)
#ifndef strnlen_user
static inline long strnlen_user(const char __user *src, long n)
+ if (!access_ok(VERIFY_READ, src, 1))
+ return 0;
return strlen((void * __force)src) + 1;

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