pstore: Protect unlink with read_mutex

When update_ms is set, pstore_get_records() will be called when there's
a new entry.  But unlink can be called at the same time and might
contend with the open-read-close loop.  Depending on the implementation
of platform driver, it may be safe or not.  But I think it'd be better
to protect those race in the first place.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 0d6bbcf..57c0646 100644 (file)
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -199,11 +199,14 @@ static int pstore_unlink(struct inode *dir, struct dentry *dentry)
        if (err)
                return err;
 
-       if (p->psi->erase)
+       if (p->psi->erase) {
+               mutex_lock(&p->psi->read_mutex);
                p->psi->erase(p->type, p->id, p->count,
                              d_inode(dentry)->i_ctime, p->psi);
-       else
+               mutex_unlock(&p->psi->read_mutex);
+       } else {
                return -EPERM;
+       }
 
        return simple_unlink(dir, dentry);
 }