[ARM] 5340/1: fix stack placement after noexecstack changes

Commit 8ec53663d2698076468b3e1edc4e1b418bd54de3 ("[ARM] Improve
non-executable support") added support for detecting non-executable
stack binaries.  One of the things it does is to make READ_IMPLIES_EXEC
be set in ->personality if we are running on a CPU that doesn't support
the XN ("Execute Never") page table bit or if we are running a binary
that needs an executable stack.

This exposed a latent bug in ARM's asm/processor.h due to which we'll
end up placing the stack at a very low address, where it will bump into
the heap on any application that uses significant amount of stack or
heap or both, causing many interesting crashes.

Fix this by testing the ADDR_LIMIT_32BIT bit in ->personality instead
of testing for equality against PER_LINUX_32BIT.

Reviewed-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 517a4d6ffc74b791691a3a2f65099bb6352e5e64..6ff33790f47b16d91054c4907edb09616a21f5d8 100644 (file)
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -23,7 +23,7 @@
 #include <asm/types.h>
 
 #ifdef __KERNEL__
-#define STACK_TOP      ((current->personality == PER_LINUX_32BIT) ? \
+#define STACK_TOP      ((current->personality & ADDR_LIMIT_32BIT) ? \
                         TASK_SIZE : TASK_SIZE_26)
 #define STACK_TOP_MAX  TASK_SIZE
 #endif