Commit 2fdb05dc authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFSv4.0: Fix a use-after-free problem in the asynchronous open() 



Yang Erkun reports that when two threads are opening files at the same
time, and are forced to abort before a reply is seen, then the call to
nfs_release_seqid() in nfs4_opendata_free() can result in a
use-after-free of the pointer to the defunct rpc task of the other
thread.
The fix is to ensure that if the RPC call is aborted before the call to
nfs_wait_on_sequence() is complete, then we must call nfs_release_seqid()
in nfs4_open_release() before the rpc_task is freed.

Reported-by: default avatarYang Erkun <yangerkun@huawei.com>
Fixes: 24ac23ab ("NFSv4: Convert open() into an asynchronous RPC call")
Reviewed-by: default avatarYang Erkun <yangerkun@huawei.com>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent c968fd23

fs/nfs/nfs4proc.c

+5 −3
Original line number Diff line number Diff line
@@ -2603,12 +2603,14 @@ static void nfs4_open_release(void *calldata) 
	struct nfs4_opendata *data = calldata;

	struct nfs4_state *state = NULL;



	/* In case of error, no cleanup! */

	if (data->rpc_status != 0 || !data->rpc_done) {

		nfs_release_seqid(data->o_arg.seqid);

		goto out_free;

	}

	/* If this request hasn't been cancelled, do nothing */

	if (!data->cancelled)

		goto out_free;

	/* In case of error, no cleanup! */

	if (data->rpc_status != 0 || !data->rpc_done)

		goto out_free;

	/* In case we need an open_confirm, no cleanup! */

	if (data->o_res.rflags & NFS4_OPEN_RESULT_CONFIRM)

		goto out_free;