[PATCH] sendfile calls lock_verify_area with wrong parameters

From: Manfred Spraul <manfred@colorfullife.com>

sendfile supports reading from a given start offset for in_file, like
pread.  But for the locks_verify_area call, in_file->f_pos is always used,
even if a start offset is used.  Result: wrong area is checked for
mandatory locks.

fs/read_write.c

@@ -559,7 +559,9 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 		goto fput_in;
 	if (!in_file->f_op || !in_file->f_op->sendfile)
 		goto fput_in;
-	retval = locks_verify_area(FLOCK_VERIFY_READ, in_inode, in_file, in_file->f_pos, count);
+	if (!ppos)
+		ppos = &in_file->f_pos;
+	retval = locks_verify_area(FLOCK_VERIFY_READ, in_inode, in_file, *ppos, count);
 	if (retval)
 		goto fput_in;
 
@@ -588,9 +590,6 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 	if (retval)
 		goto fput_out;
 
-	if (!ppos)
-		ppos = &in_file->f_pos;
-
 	if (!max)
 		max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);