linux/net/sunrpc
Jason Baron 3dedbb5ca1 rpc: Add -EPERM processing for xs_udp_send_request()
If an iptables drop rule is added for an nfs server, the client can end up in
a softlockup. Because of the way that xs_sendpages() is structured, the -EPERM
is ignored since the prior bits of the packet may have been successfully queued
and thus xs_sendpages() returns a non-zero value. Then, xs_udp_send_request()
thinks that because some bits were queued it should return -EAGAIN. We then try
the request again and again, resulting in cpu spinning. Reproducer:

1) open a file on the nfs server '/nfs/foo' (mounted using udp)
2) iptables -A OUTPUT -d <nfs server ip> -j DROP
3) write to /nfs/foo
4) close /nfs/foo
5) iptables -D OUTPUT -d <nfs server ip> -j DROP

The softlockup occurs in step 4 above.

The previous patch, allows xs_sendpages() to return both a sent count and
any error values that may have occurred. Thus, if we get an -EPERM, return
that to the higher level code.

With this patch in place we can successfully abort the above sequence and
avoid the softlockup.

I also tried the above test case on an nfs mount on tcp and although the system
does not softlockup, I still ended up with the 'hung_task' firing after 120
seconds, due to the i/o being stuck. The tcp case appears a bit harder to fix,
since -EPERM appears to get ignored much lower down in the stack and does not
propogate up to xs_sendpages(). This case is not quite as insidious as the
softlockup and it is not addressed here.

Reported-by: Yigong Lou <ylou@akamai.com>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2014-09-24 23:13:46 -04:00
..
auth_gss NFS client updates for Linux 3.17 2014-08-13 18:13:19 -06:00
xprtrdma NFS client updates for Linux 3.17 2014-08-13 18:13:19 -06:00
addr.c replace strict_strto calls 2014-07-12 18:45:49 -04:00
auth_generic.c sunrpc/auth: allow lockless (rcu) lookup of credential cache. 2014-08-03 17:14:12 -04:00
auth_null.c sunrpc/auth: allow lockless (rcu) lookup of credential cache. 2014-08-03 17:14:12 -04:00
auth_unix.c SUNRPC refactor rpcauth_checkverf error returns 2013-09-03 15:25:09 -04:00
auth.c SUNRPC: remove all refcounting of groupinfo from rpcauth_lookupcred 2014-08-04 09:22:08 -04:00
backchannel_rqst.c arch: Mass conversion of smp_mb__*() 2014-04-18 14:20:48 +02:00
bc_svc.c SUNRPC: remove BUG_ON from bc_send 2012-11-04 14:43:41 -05:00
cache.c SUNRPC: Fix printk that is not only for nfsd 2014-05-08 14:59:51 -04:00
clnt.c rpc: Add -EPERM processing for xs_udp_send_request() 2014-09-24 23:13:46 -04:00
Kconfig xprtrdma: add separate Kconfig options for NFSoRDMA client and server support 2014-03-28 18:02:12 -04:00
Makefile xprtrdma: add separate Kconfig options for NFSoRDMA client and server support 2014-03-28 18:02:12 -04:00
netns.h Merge branch 'for-3.14' of git://linux-nfs.org/~bfields/linux 2014-01-30 10:18:43 -08:00
rpc_pipe.c rpc_pipe: Drop memory allocation cast 2014-07-12 18:43:44 -04:00
rpcb_clnt.c SUNRPC: If the rpcbind channel is disconnected, fail the call to unregister 2013-08-07 17:07:18 -04:00
sched.c sched: Allow wait_on_bit_action() functions to support a timeout 2014-07-16 15:10:41 +02:00
socklib.c net: Save software checksum complete 2014-06-11 15:46:13 -07:00
stats.c SUNRPC: Deprecate rpc_client->cl_protname 2013-08-30 09:19:34 -04:00
sunrpc_syms.c sunrpc: create a new dummy pipe for gssd to hold open 2013-12-06 13:06:30 -05:00
sunrpc.h SUNRPC: track whether a request is coming from a loop-back interface. 2014-05-22 15:59:18 -04:00
svc_xprt.c SUNRPC: Allow svc_reserve() to notify TCP socket that space has been freed 2014-07-29 16:10:20 -04:00
svc.c SUNRPC/NFSD: Change to type of bool for rq_usedeferral and rq_splice_ok 2014-06-23 11:31:36 -04:00
svcauth_unix.c svcrpc: fix failures to handle -1 uid's 2013-07-08 17:27:23 -04:00
svcauth.c nfsd4: better reservation of head space for krb5 2014-05-30 17:32:17 -04:00
svcsock.c SUNRPC: Allow svc_reserve() to notify TCP socket that space has been freed 2014-07-29 16:10:20 -04:00
sysctl.c net: Convert uses of typedef ctl_table to struct ctl_table 2013-06-13 02:36:09 -07:00
timer.c net: cleanup unsigned to unsigned int 2012-04-15 12:44:40 -04:00
xdr.c SUNRPC: xdr_get_next_encode_buffer should be declared static 2014-07-18 11:35:46 -04:00
xprt.c NFS client updates for Linux 3.17 2014-08-13 18:13:19 -06:00
xprtsock.c rpc: Add -EPERM processing for xs_udp_send_request() 2014-09-24 23:13:46 -04:00