[PATCH] security: revalidate rw permissions for sys_splice and sys_vmsplice

[James Morris <jmorris@namei.org>]

Revalidate read/write permissions for splice(2) and vmslice(2), in case 
security policy has changed since the files were opened.

Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
---

Updated version against latest Linus git.  Jens, I dropped your initial 
signed-off-by due to the rework.

Please review and apply if ok.


 fs/splice.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index ed2ce99..ef80822 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -28,6 +28,7 @@
 #include <linux/module.h>
 #include <linux/syscalls.h>
 #include <linux/uio.h>
+#include <linux/security.h>
 
 /*
  * Attempt to steal a page from a pipe buffer. This should perhaps go into
@@ -961,6 +962,10 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 	if (unlikely(ret < 0))
 		return ret;
 
+	ret = security_file_permission(out, MAY_WRITE);
+	if (unlikely(ret < 0))
+		return ret;
+
 	return out->f_op->splice_write(pipe, out, ppos, len, flags);
 }
 
@@ -983,6 +988,10 @@ static long do_splice_to(struct file *in, loff_t *ppos,
 	if (unlikely(ret < 0))
 		return ret;
 
+	ret = security_file_permission(in, MAY_READ);
+	if (unlikely(ret < 0))
+		return ret;
+
 	return in->f_op->splice_read(in, ppos, pipe, len, flags);
 }
 
-- 
1.5.2.1