ARC: mm: allow mprotect to make stack mappings executable

commit 93312b6da4df31e4102ce5420e6217135a16c7ea upstream.

mprotect(EXEC) was failing for stack mappings as default vm flags was
missing MAYEXEC.

This was triggered by glibc test suite nptl/tst-execstack testcase

What is surprising is that despite running LTP for years on, we didn't
catch this issue as it lacks a directed test case.

gcc dejagnu tests with nested functions also requiring exec stack work
fine though because they rely on the GNU_STACK segment spit out by
compiler and handled in kernel elf loader.

This glibc case is different as the stack is non exec to begin with and
a dlopen of shared lib with GNU_STACK segment triggers the exec stack
proceedings using a mprotect(PROT_EXEC) which was broken.

CC: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
index 9c8aa41e45c2248b0ee39a23c3802e4f7425d358..25f6583a7a2c8e28d04df9cd6477107fb2dd3534 100644 (file)
--- a/arch/arc/include/asm/page.h
+++ b/arch/arc/include/asm/page.h
@@ -97,7 +97,7 @@ typedef unsigned long pgtable_t;
 #define virt_addr_valid(kaddr)  pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
 
 /* Default Permissions for stack/heaps pages (Non Executable) */
-#define VM_DATA_DEFAULT_FLAGS   (VM_READ | VM_WRITE | VM_MAYREAD | VM_MAYWRITE)
+#define VM_DATA_DEFAULT_FLAGS   (VM_READ | VM_WRITE | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
 
 #define WANT_PAGE_VIRTUAL   1