[PATCH 3/6][TAKE7] revalidate write permissions for fallocate

["Amit K. Arora" <aarora@xxxxxxxxxxxxxxxxxx>]

From: David P. Quigley <dpquigl@xxxxxxxxxxxxx>

Revalidate the write permissions for fallocate(2), in case security policy has
changed since the files were opened.

Acked-by: James Morris <jmorris@xxxxxxxxx>
Signed-off-by: David P. Quigley <dpquigl@xxxxxxxxxxxxx>

---
 fs/open.c |    3 +++
 1 files changed, 3 insertions(+)

Index: linux-2.6.22/fs/open.c
===================================================================
--- linux-2.6.22.orig/fs/open.c
+++ linux-2.6.22/fs/open.c
@@ -407,6 +407,9 @@ asmlinkage long sys_fallocate(int fd, in
                goto out;
        if (!(file->f_mode & FMODE_WRITE))
                goto out_fput;
+       ret = security_file_permission(file, MAY_WRITE);
+       if (ret)
+               goto out_fput;
 
        inode = file->f_path.dentry->d_inode;