From 7e2cff42cfac27c25202648c5c89f9171e5bc085 Mon Sep 17 00:00:00 2001 From: Paolo 'Blaisorblade' Giarrusso Date: Wed, 21 Sep 2005 09:55:39 -0700 Subject: [PATCH] mm: add a note about partially hardcoded VM_* flags Hugh made me note this line for permission checking in mprotect(): if ((newflags & ~(newflags >> 4)) & 0xf) { after figuring out what's that about, I decided it's nasty enough. Btw Hugh itself didn't like the 0xf. We can safely change it to VM_READ|VM_WRITE|VM_EXEC because we never change VM_SHARED, so no need to check that. Signed-off-by: Paolo 'Blaisorblade' Giarrusso Acked-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mprotect.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'mm/mprotect.c') diff --git a/mm/mprotect.c b/mm/mprotect.c index e9fbd013ad9..57577f63b30 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -248,7 +248,8 @@ sys_mprotect(unsigned long start, size_t len, unsigned long prot) newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); - if ((newflags & ~(newflags >> 4)) & 0xf) { + /* newflags >> 4 shift VM_MAY% in place of VM_% */ + if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { error = -EACCES; goto out; } -- cgit v1.2.3