[PATCH 2/3] uprobes: Change valid_vma() to demand VM_MAYEXEC rather than VM_EXEC

[Oleg Nesterov <oleg@redhat.com>]

uprobe_register() or uprobe_mmap() requires VM_READ | VM_EXEC, this
is not right. An apllication can do mprotect(PROT_EXEC) later and
execute this code.

Change valid_vma(is_register => true) to check VM_MAYEXEC instead.
No need to check VM_MAYREAD, it is always set.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/events/uprobes.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index fa1579a..b9b50dd 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -106,8 +106,8 @@ static bool valid_vma(struct vm_area_struct *vma, bool is_register)
 	if (!is_register)
 		return true;
 
-	if ((vma->vm_flags & (VM_HUGETLB|VM_READ|VM_WRITE|VM_EXEC|VM_SHARED))
-				== (VM_READ|VM_EXEC))
+	if ((vma->vm_flags & (VM_HUGETLB | VM_WRITE | VM_MAYEXEC | VM_SHARED))
+				== VM_MAYEXEC)
 		return true;
 
 	return false;
-- 
1.5.5.1