From: minoura makoto minoura@valinux.co.jp
[ Upstream commit b18cba09e374637a0a3759d856a6bca94c133952 ]
Commit 9130b8dbc6ac ("SUNRPC: allow for upcalls for the same uid but different gss service") introduced `auth` argument to __gss_find_upcall(), but in gss_pipe_downcall() it was left as NULL since it (and auth->service) was not (yet) determined.
When multiple upcalls with the same uid and different service are ongoing, it could happen that __gss_find_upcall(), which returns the first match found in the pipe->in_downcall list, could not find the correct gss_msg corresponding to the downcall we are looking for. Moreover, it might return a msg which is not sent to rpc.gssd yet.
We could see mount.nfs process hung in D state with multiple mount.nfs are executed in parallel. The call trace below is of CentOS 7.9 kernel-3.10.0-1160.24.1.el7.x86_64 but we observed the same hang w/ elrepo kernel-ml-6.0.7-1.el7.
PID: 71258 TASK: ffff91ebd4be0000 CPU: 36 COMMAND: "mount.nfs" #0 [ffff9203ca3234f8] __schedule at ffffffffa3b8899f #1 [ffff9203ca323580] schedule at ffffffffa3b88eb9 #2 [ffff9203ca323590] gss_cred_init at ffffffffc0355818 [auth_rpcgss] #3 [ffff9203ca323658] rpcauth_lookup_credcache at ffffffffc0421ebc [sunrpc] #4 [ffff9203ca3236d8] gss_lookup_cred at ffffffffc0353633 [auth_rpcgss] #5 [ffff9203ca3236e8] rpcauth_lookupcred at ffffffffc0421581 [sunrpc] #6 [ffff9203ca323740] rpcauth_refreshcred at ffffffffc04223d3 [sunrpc] #7 [ffff9203ca3237a0] call_refresh at ffffffffc04103dc [sunrpc] #8 [ffff9203ca3237b8] __rpc_execute at ffffffffc041e1c9 [sunrpc] #9 [ffff9203ca323820] rpc_execute at ffffffffc0420a48 [sunrpc]
The scenario is like this. Let's say there are two upcalls for services A and B, A -> B in pipe->in_downcall, B -> A in pipe->pipe.
When rpc.gssd reads pipe to get the upcall msg corresponding to service B from pipe->pipe and then writes the response, in gss_pipe_downcall the msg corresponding to service A will be picked because only uid is used to find the msg and it is before the one for B in pipe->in_downcall. And the process waiting for the msg corresponding to service A will be woken up.
Actual scheduing of that process might be after rpc.gssd processes the next msg. In rpc_pipe_generic_upcall it clears msg->errno (for A). The process is scheduled to see gss_msg->ctx == NULL and gss_msg->msg.errno == 0, therefore it cannot break the loop in gss_create_upcall and is never woken up after that.
This patch adds a simple check to ensure that a msg which is not sent to rpc.gssd yet is not chosen as the matching upcall upon receiving a downcall.
Signed-off-by: minoura makoto minoura@valinux.co.jp Signed-off-by: Hiroshi Shimamoto h-shimamoto@nec.com Tested-by: Hiroshi Shimamoto h-shimamoto@nec.com Cc: Trond Myklebust trondmy@hammerspace.com Fixes: 9130b8dbc6ac ("SUNRPC: allow for upcalls for same uid but different gss service") Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/sunrpc/rpc_pipe_fs.h | 5 +++++ net/sunrpc/auth_gss/auth_gss.c | 19 +++++++++++++++++-- 2 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/include/linux/sunrpc/rpc_pipe_fs.h b/include/linux/sunrpc/rpc_pipe_fs.h index e90b9bd99ded..396de2ef8767 100644 --- a/include/linux/sunrpc/rpc_pipe_fs.h +++ b/include/linux/sunrpc/rpc_pipe_fs.h @@ -94,6 +94,11 @@ extern ssize_t rpc_pipe_generic_upcall(struct file *, struct rpc_pipe_msg *, char __user *, size_t); extern int rpc_queue_upcall(struct rpc_pipe *, struct rpc_pipe_msg *);
+/* returns true if the msg is in-flight, i.e., already eaten by the peer */ +static inline bool rpc_msg_is_inflight(const struct rpc_pipe_msg *msg) { + return (msg->copied != 0 && list_empty(&msg->list)); +} + struct rpc_clnt; extern struct dentry *rpc_create_client_dir(struct dentry *, const char *, struct rpc_clnt *); extern int rpc_remove_client_dir(struct rpc_clnt *); diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c index e61c48c1b37d..c11e68539602 100644 --- a/net/sunrpc/auth_gss/auth_gss.c +++ b/net/sunrpc/auth_gss/auth_gss.c @@ -323,7 +323,7 @@ __gss_find_upcall(struct rpc_pipe *pipe, kuid_t uid, const struct gss_auth *auth list_for_each_entry(pos, &pipe->in_downcall, list) { if (!uid_eq(pos->uid, uid)) continue; - if (auth && pos->auth->service != auth->service) + if (pos->auth->service != auth->service) continue; refcount_inc(&pos->count); dprintk("RPC: %s found msg %p\n", __func__, pos); @@ -677,6 +677,21 @@ gss_create_upcall(struct gss_auth *gss_auth, struct gss_cred *gss_cred) return err; }
+static struct gss_upcall_msg * +gss_find_downcall(struct rpc_pipe *pipe, kuid_t uid) +{ + struct gss_upcall_msg *pos; + list_for_each_entry(pos, &pipe->in_downcall, list) { + if (!uid_eq(pos->uid, uid)) + continue; + if (!rpc_msg_is_inflight(&pos->msg)) + continue; + refcount_inc(&pos->count); + return pos; + } + return NULL; +} + #define MSG_BUF_MAXSIZE 1024
static ssize_t @@ -723,7 +738,7 @@ gss_pipe_downcall(struct file *filp, const char __user *src, size_t mlen) err = -ENOENT; /* Find a matching upcall */ spin_lock(&pipe->lock); - gss_msg = __gss_find_upcall(pipe, uid, NULL); + gss_msg = gss_find_downcall(pipe, uid); if (gss_msg == NULL) { spin_unlock(&pipe->lock); goto err_put_ctx;