[PATCH] LSM: add missing hook to do_compat_readv_writev()

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@namei.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/compat.c b/fs/compat.c
index 7f8e26e..2e32bd3 100644 (file)
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1217,6 +1217,10 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
        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;