uaccess: fix integer overflow on access_ok()

Three architectures check the end of a user access against the
address limit without taking a possible overflow into account.
Passing a negative length or another overflow in here returns
success when it should not.

Use the most common correct implementation here, which optimizes
for a constant 'size' argument, and turns the common case into a
single comparison.

Cc: stable@vger.kernel.org
Fixes: da551281947c ("csky: User access")
Fixes: f663b60f5215 ("microblaze: Fix uaccess_ok macro")
Fixes: 7567746e1c0d ("Hexagon: Add user access functions")
Reported-by: David Laight <David.Laight@aculab.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 9 insertions, 9 deletions

diff --git a/arch/hexagon/include/asm/uaccess.h b/arch/hexagon/include/asm/uaccess.h
index ef5bfef8d490..719ba3f3c45c 100644
--- a/arch/hexagon/include/asm/uaccess.h
+++ b/arch/hexagon/include/asm/uaccess.h
@@ -25,17 +25,17 @@
  * Returns true (nonzero) if the memory block *may* be valid, false (zero)
  * if it is definitely invalid.
  *
- * User address space in Hexagon, like x86, goes to 0xbfffffff, so the
- * simple MSB-based tests used by MIPS won't work.  Some further
- * optimization is probably possible here, but for now, keep it
- * reasonably simple and not *too* slow.  After all, we've got the
- * MMU for backup.
  */
+#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
+#define user_addr_max() (uaccess_kernel() ? ~0UL : TASK_SIZE)
 
-#define __access_ok(addr, size) \
-	((get_fs().seg == KERNEL_DS.seg) || \
-	(((unsigned long)addr < get_fs().seg) && \
-	  (unsigned long)size < (get_fs().seg - (unsigned long)addr)))
+static inline int __access_ok(unsigned long addr, unsigned long size)
+{
+	unsigned long limit = TASK_SIZE;
+
+	return (size <= limit) && (addr <= (limit - size));
+}
+#define __access_ok __access_ok
 
 /*
  * When a kernel-mode page fault is taken, the faulting instruction