SUNRPC: Fix race corrupting rpc upcall
If rpc_queue_upcall() adds a new upcall to the rpci->pipe list just
after rpc_pipe_release calls rpc_purge_list(), but before it calls
gss_pipe_release (as rpci->ops->release_pipe(inode)), then the latter
will free a message without deleting it from the rpci->pipe list.
We will be left with a freed object on the rpc->pipe list. Most
frequent symptoms are kernel crashes in rpc.gssd system calls on the
pipe in question.
Reported-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index dcfc66b..12c4859 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -745,17 +745,18 @@
struct rpc_inode *rpci = RPC_I(inode);
struct gss_upcall_msg *gss_msg;
+restart:
spin_lock(&inode->i_lock);
- while (!list_empty(&rpci->in_downcall)) {
+ list_for_each_entry(gss_msg, &rpci->in_downcall, list) {
- gss_msg = list_entry(rpci->in_downcall.next,
- struct gss_upcall_msg, list);
+ if (!list_empty(&gss_msg->msg.list))
+ continue;
gss_msg->msg.errno = -EPIPE;
atomic_inc(&gss_msg->count);
__gss_unhash_msg(gss_msg);
spin_unlock(&inode->i_lock);
gss_release_msg(gss_msg);
- spin_lock(&inode->i_lock);
+ goto restart;
}
spin_unlock(&inode->i_lock);