[JFFS2] Fix race in setting file attributes

It seems like there is a potential race in the function jffs2_do_setattr()
in the case when attributes of a symlink are updated. The symlink metadata
is read without having f->sem locked.

The following patch should fix the race.

Signed-off-by: Dmitry Bazhenov <atrey@emcraft.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c
index 09e5d10b88401ca736bbd70d099d847fd9698bed..ea1f37d4fc5867deb21f46e6539721cb70dd42a5 100644 (file)
--- a/fs/jffs2/fs.c
+++ b/fs/jffs2/fs.c
@@ -56,15 +56,20 @@ static int jffs2_do_setattr (struct inode *inode, struct iattr *iattr)
                mdatalen = sizeof(dev);
                D1(printk(KERN_DEBUG "jffs2_setattr(): Writing %d bytes of kdev_t\n", mdatalen));
        } else if (S_ISLNK(inode->i_mode)) {
+               down(&f->sem);
                mdatalen = f->metadata->size;
                mdata = kmalloc(f->metadata->size, GFP_USER);
-               if (!mdata)
+               if (!mdata) {
+                       up(&f->sem);
                        return -ENOMEM;
+               }
                ret = jffs2_read_dnode(c, f, f->metadata, mdata, 0, mdatalen);
                if (ret) {
+                       up(&f->sem);
                        kfree(mdata);
                        return ret;
                }
+               up(&f->sem);
                D1(printk(KERN_DEBUG "jffs2_setattr(): Writing %d bytes of symlink target\n", mdatalen));
        }