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From:   Scott Mayhew <smayhew@redhat.com>
To:     bfields@fieldses.org, chuck.lever@oracle.com
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH] nfsd: avoid a NULL dereference in __cld_pipe_upcall()
Date:   Fri, 10 Jul 2020 16:33:07 -0400
Message-Id: <20200710203307.2545412-1-smayhew@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

If the rpc_pipefs is unmounted, then the rpc_pipe->dentry becomes NULL
and dereferencing the dentry->d_sb will trigger an oops.  The only
reason we're doing that is to determine the nfsd_net, which could
instead be passed in by the caller.  So do that instead.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
---
 fs/nfsd/nfs4recover.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 9e40dfecf1b1..186fa2c2c6ba 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -747,13 +747,11 @@ struct cld_upcall {
 };
 
 static int
-__cld_pipe_upcall(struct rpc_pipe *pipe, void *cmsg)
+__cld_pipe_upcall(struct rpc_pipe *pipe, void *cmsg, struct nfsd_net *nn)
 {
 	int ret;
 	struct rpc_pipe_msg msg;
 	struct cld_upcall *cup = container_of(cmsg, struct cld_upcall, cu_u);
-	struct nfsd_net *nn = net_generic(pipe->dentry->d_sb->s_fs_info,
-					  nfsd_net_id);
 
 	memset(&msg, 0, sizeof(msg));
 	msg.data = cmsg;
@@ -773,7 +771,7 @@ __cld_pipe_upcall(struct rpc_pipe *pipe, void *cmsg)
 }
 
 static int
-cld_pipe_upcall(struct rpc_pipe *pipe, void *cmsg)
+cld_pipe_upcall(struct rpc_pipe *pipe, void *cmsg, struct nfsd_net *nn)
 {
 	int ret;
 
@@ -782,7 +780,7 @@ cld_pipe_upcall(struct rpc_pipe *pipe, void *cmsg)
 	 *  upcalls queued.
 	 */
 	do {
-		ret = __cld_pipe_upcall(pipe, cmsg);
+		ret = __cld_pipe_upcall(pipe, cmsg, nn);
 	} while (ret == -EAGAIN);
 
 	return ret;
@@ -1115,7 +1113,7 @@ nfsd4_cld_create(struct nfs4_client *clp)
 	memcpy(cup->cu_u.cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
 			clp->cl_name.len);
 
-	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg);
+	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg, nn);
 	if (!ret) {
 		ret = cup->cu_u.cu_msg.cm_status;
 		set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
@@ -1180,7 +1178,7 @@ nfsd4_cld_create_v2(struct nfs4_client *clp)
 	} else
 		cmsg->cm_u.cm_clntinfo.cc_princhash.cp_len = 0;
 
-	ret = cld_pipe_upcall(cn->cn_pipe, cmsg);
+	ret = cld_pipe_upcall(cn->cn_pipe, cmsg, nn);
 	if (!ret) {
 		ret = cmsg->cm_status;
 		set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
@@ -1218,7 +1216,7 @@ nfsd4_cld_remove(struct nfs4_client *clp)
 	memcpy(cup->cu_u.cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
 			clp->cl_name.len);
 
-	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg);
+	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg, nn);
 	if (!ret) {
 		ret = cup->cu_u.cu_msg.cm_status;
 		clear_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
@@ -1261,7 +1259,7 @@ nfsd4_cld_check_v0(struct nfs4_client *clp)
 	memcpy(cup->cu_u.cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
 			clp->cl_name.len);
 
-	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg);
+	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg, nn);
 	if (!ret) {
 		ret = cup->cu_u.cu_msg.cm_status;
 		set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
@@ -1404,7 +1402,7 @@ nfsd4_cld_grace_start(struct nfsd_net *nn)
 	}
 
 	cup->cu_u.cu_msg.cm_cmd = Cld_GraceStart;
-	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg);
+	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg, nn);
 	if (!ret)
 		ret = cup->cu_u.cu_msg.cm_status;
 
@@ -1432,7 +1430,7 @@ nfsd4_cld_grace_done_v0(struct nfsd_net *nn)
 
 	cup->cu_u.cu_msg.cm_cmd = Cld_GraceDone;
 	cup->cu_u.cu_msg.cm_u.cm_gracetime = nn->boot_time;
-	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg);
+	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg, nn);
 	if (!ret)
 		ret = cup->cu_u.cu_msg.cm_status;
 
@@ -1460,7 +1458,7 @@ nfsd4_cld_grace_done(struct nfsd_net *nn)
 	}
 
 	cup->cu_u.cu_msg.cm_cmd = Cld_GraceDone;
-	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg);
+	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg, nn);
 	if (!ret)
 		ret = cup->cu_u.cu_msg.cm_status;
 
@@ -1524,7 +1522,7 @@ nfsd4_cld_get_version(struct nfsd_net *nn)
 		goto out_err;
 	}
 	cup->cu_u.cu_msg.cm_cmd = Cld_GetVersion;
-	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg);
+	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_u.cu_msg, nn);
 	if (!ret) {
 		ret = cup->cu_u.cu_msg.cm_status;
 		if (ret)
-- 
2.25.4