[PATCH 4/4] Annotate struct fs_struct's usage count restriction

[Hugh Dickins]

From: David Howells <dhowells@xxxxxxxxxx>

Annotate struct fs_struct's usage count to indicate the restrictions upon it.
It may not be incremented, except by clone(CLONE_FS), as this affects the
check in check_unsafe_exec() in fs/exec.c.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxx
---

 include/linux/fs_struct.h |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- 2.6.29/include/linux/fs_struct.h	2009-03-23 23:12:14.000000000 +0000
+++ linux/include/linux/fs_struct.h	2009-03-28 18:06:02.000000000 +0000
@@ -4,7 +4,10 @@
 #include <linux/path.h>
 
 struct fs_struct {
-	atomic_t count;
+	atomic_t count;	/* This usage count is used by check_unsafe_exec() for
+			 * security checking purposes - therefore it may not be
+			 * incremented, except by clone(CLONE_FS).
+			 */
 	rwlock_t lock;
 	int umask;
 	struct path root, pwd;
--
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