[patch 18/24] LSM: add missing hook to do_compat_readv_writev()

[Greg KH]

-stable review patch.  If anyone has any objections, please let us know.

------------------
From: James Morris <jmorris@xxxxxxxxx>

This patch addresses a flaw in LSM, where there is no mediation of readv()
and writev() in for 32-bit compatible apps using a 64-bit kernel.

This bug was discovered and fixed initially in the native readv/writev
code [1], but was not fixed in the compat code.  Thanks to Al for spotting
this one.

  [1] http://lwn.net/Articles/154282/

Signed-off-by: James Morris <jmorris@xxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>

---
 fs/compat.c |    4 ++++
 1 file changed, 4 insertions(+)

--- linux-2.6.16.11.orig/fs/compat.c
+++ linux-2.6.16.11/fs/compat.c
@@ -1215,6 +1215,10 @@ static ssize_t compat_do_readv_writev(in
 	if (ret < 0)
 		goto out;
 
+	ret = security_file_permission(file, type == READ ? MAY_READ:MAY_WRITE);
+	if (ret)
+		goto out;
+
 	fnv = NULL;
 	if (type == READ) {
 		fn = file->f_op->read;

--
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