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asm-generic: uaccess: add missing access_ok() check to strnlen_user()

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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@gentoo.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Mike Frysinger 2009-06-14 02:00:02 -04:00 committed by Arnd Bergmann
parent 0732f87761
commit 9844813f22
1 changed files with 2 additions and 0 deletions
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include/asm-generic/uaccess.h
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@ -291,6 +291,8 @@ strncpy_from_user(char *dst, const char __user *src, long count)
#ifndef strnlen_user #ifndef strnlen_user
static inline long strnlen_user(const char __user *src, long n) 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; return strlen((void * __force)src) + 1;
} }
#endif #endif