[ Upstream commit b18cba09e374637a0a3759d856a6bca94c133952 ]
Commit 9130b8dbc6 ("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: 9130b8dbc6 ("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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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