[patch] remove MNT_NOEXEC check for PROT_EXEC mmaps

[Stas Sergeev]

Hi Andrew.

I am not sure at all whether this patch is appreciated
or not. The on-list query yielded no results, but I have
to try. :)

This patch removes the MNT_NOEXEC check for the PROT_EXEC
mappings. That allows to mount tmpfs with "noexec" option
without breaking the existing apps, which is what debian
wants to do for sequrity reasons:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=386945
More details here:
http://uwsg.ucs.indiana.edu/hypermail/linux/kernel/0609.2/1537.html

Signed-off-by: Stas Sergeev <stsp@xxxxxxxx>

--- a/mm/mmap.c	2006-01-25 15:02:24.000000000 +0300
+++ b/mm/mmap.c	2006-09-21 13:19:15.000000000 +0400
@@ -899,10 +899,6 @@
 
 		if (!file->f_op || !file->f_op->mmap)
 			return -ENODEV;
-
-		if ((prot & PROT_EXEC) &&
-		    (file->f_vfsmnt->mnt_flags & MNT_NOEXEC))
-			return -EPERM;
 	}
 	/*
 	 * Does the application expect PROT_READ to imply PROT_EXEC?
@@ -911,8 +907,7 @@
 	 *  mounted, in which case we dont add PROT_EXEC.)
 	 */
 	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
-		if (!(file && (file->f_vfsmnt->mnt_flags & MNT_NOEXEC)))
-			prot |= PROT_EXEC;
+		prot |= PROT_EXEC;
 
 	if (!len)
 		return -EINVAL;
--- a/mm/nommu.c	2006-04-12 09:37:34.000000000 +0400
+++ b/mm/nommu.c	2006-09-21 13:21:32.000000000 +0400
@@ -493,13 +493,7 @@
 				capabilities &= ~BDI_CAP_MAP_DIRECT;
 		}
 
-		/* handle executable mappings and implied executable
-		 * mappings */
-		if (file->f_vfsmnt->mnt_flags & MNT_NOEXEC) {
-			if (prot & PROT_EXEC)
-				return -EPERM;
-		}
-		else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
+		if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
 			/* handle implication of PROT_EXEC by PROT_READ */
 			if (current->personality & READ_IMPLIES_EXEC) {
 				if (capabilities & BDI_CAP_EXEC_MAP)