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Subject[PATCH] asm-generic: uaccess: fix up local access_ok() usage
Date
There's no reason that I can see to use the short __access_ok() form
directly when the access_ok() is clearer in intent and for more people,
expands to the same C code (i.e. always specify the first field -- access
type). Not all no-mmu systems lack memory protection, so the read/write
could feasibly be checked.

Also, the strnlen_user() function was missing a access_ok() check on the
pointer given. We've had cases on Blackfin systems where test cases
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>
---
include/asm-generic/uaccess.h | 14 ++++++++------
1 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index 6d8cab2..705410b 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -163,7 +163,7 @@ static inline __must_check long __copy_to_user(void __user *to,
#define put_user(x, ptr) \
({ \
might_sleep(); \
- __access_ok(ptr, sizeof (*ptr)) ? \
+ access_ok(VERIFY_WRITE, ptr, sizeof (*ptr)) ? \
__put_user(x, ptr) : \
-EFAULT; \
})
@@ -219,7 +219,7 @@ extern int __put_user_bad(void) __attribute__((noreturn));
#define get_user(x, ptr) \
({ \
might_sleep(); \
- __access_ok(ptr, sizeof (*ptr)) ? \
+ access_ok(VERIFY_READ, ptr, sizeof (*ptr)) ? \
__get_user(x, ptr) : \
-EFAULT; \
})
@@ -244,7 +244,7 @@ static inline long copy_from_user(void *to,
const void __user * from, unsigned long n)
{
might_sleep();
- if (__access_ok(from, n))
+ if (access_ok(VERIFY_READ, from, n))
return __copy_from_user(to, from, n);
else
return n;
@@ -254,7 +254,7 @@ static inline long copy_to_user(void __user *to,
const void *from, unsigned long n)
{
might_sleep();
- if (__access_ok(to, n))
+ if (access_ok(VERIFY_WRITE, to, n))
return __copy_to_user(to, from, n);
else
return n;
@@ -278,7 +278,7 @@ __strncpy_from_user(char *dst, const char __user *src, long count)
static inline long
strncpy_from_user(char *dst, const char __user *src, long count)
{
- if (!__access_ok(src, 1))
+ if (!access_ok(VERIFY_READ, src, 1))
return -EFAULT;
return __strncpy_from_user(dst, src, count);
}
@@ -291,6 +291,8 @@ 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;
}
#endif
@@ -316,7 +318,7 @@ static inline __must_check unsigned long
clear_user(void __user *to, unsigned long n)
{
might_sleep();
- if (!__access_ok(to, n))
+ if (!access_ok(VERIFY_WRITE, to, n))
return n;

return __clear_user(to, n);
--
1.6.3.1


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