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Subject[119/123] SUNRPC: Fix race corrupting rpc upcall
From: Trond Myklebust <Trond.Myklebust@netapp.com>

commit 5a67657a2e90c9e4a48518f95d4ba7777aa20fbb upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
net/sunrpc/auth_gss/auth_gss.c | 9 +++++----
net/sunrpc/rpc_pipe.c | 6 +++---
2 files changed, 8 insertions(+), 7 deletions(-)

--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -717,17 +717,18 @@ gss_pipe_release(struct inode *inode)
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);

--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -47,7 +47,7 @@ static void rpc_purge_list(struct rpc_in
return;
do {
msg = list_entry(head->next, struct rpc_pipe_msg, list);
- list_del(&msg->list);
+ list_del_init(&msg->list);
msg->errno = err;
destroy_msg(msg);
} while (!list_empty(head));
@@ -207,7 +207,7 @@ rpc_pipe_release(struct inode *inode, st
if (msg != NULL) {
spin_lock(&inode->i_lock);
msg->errno = -EAGAIN;
- list_del(&msg->list);
+ list_del_init(&msg->list);
spin_unlock(&inode->i_lock);
rpci->ops->destroy_msg(msg);
}
@@ -267,7 +267,7 @@ rpc_pipe_read(struct file *filp, char __
if (res < 0 || msg->len == msg->copied) {
filp->private_data = NULL;
spin_lock(&inode->i_lock);
- list_del(&msg->list);
+ list_del_init(&msg->list);
spin_unlock(&inode->i_lock);
rpci->ops->destroy_msg(msg);
}



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