[Trusty][CVE-2014-7822][PATCH 1/1] splice: Apply generic position and size checks to each write

[Luis Henriques]

From: Ben Hutchings <ben at decadent.org.uk>

We need to check the position and size of file writes against various
limits, using generic_write_check().  This was not being done for
the splice write path.  It was fixed upstream by commit 8d0207652cbe
("->splice_write() via ->write_iter()") but we can't apply that.

CVE-2014-7822

Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
[ kamal: port to 3.13-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
CVE-2014-7822
BugLink: http://bugs.launchpad.net/bugs/1416498
[ luis: cherry-picked from stable linux-3.13.y-queue branch ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ocfs2/file.c | 8 ++++++--
 fs/splice.c     | 8 ++++++--
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 9c6594997323..5850a816704e 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2449,9 +2449,7 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
 	struct address_space *mapping = out->f_mapping;
 	struct inode *inode = mapping->host;
 	struct splice_desc sd = {
-		.total_len = len,
 		.flags = flags,
-		.pos = *ppos,
 		.u.file = out,
 	};
 
@@ -2461,6 +2459,12 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
 			out->f_path.dentry->d_name.len,
 			out->f_path.dentry->d_name.name, len);
 
+	ret = generic_write_checks(out, ppos, &len, 0);
+	if (ret)
+		return ret;
+	sd.total_len = len;
+	sd.pos = *ppos;
+
 	pipe_lock(pipe);
 
 	splice_from_pipe_begin(&sd);
diff --git a/fs/splice.c b/fs/splice.c
index 3ff6576aeae7..0c6c0b777b34 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1012,13 +1012,17 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 	struct address_space *mapping = out->f_mapping;
 	struct inode *inode = mapping->host;
 	struct splice_desc sd = {
-		.total_len = len,
 		.flags = flags,
-		.pos = *ppos,
 		.u.file = out,
 	};
 	ssize_t ret;
 
+	ret = generic_write_checks(out, ppos, &len, S_ISBLK(inode->i_mode));
+	if (ret)
+		return ret;
+	sd.total_len = len;
+	sd.pos = *ppos;
+
 	pipe_lock(pipe);
 
 	splice_from_pipe_begin(&sd);