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From: Borislav Petkov <petkov@uni-muenster.de>
Subject: Re: 2.6.11-mm3: BUG: atomic counter underflow at: rpcauth_destroy
Date: Tue, 15 Mar 2005 23:21:52 +0100
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On Tuesday 15 March 2005 13:32, you wrote:
> Hi there!

Hi,
I got those too..

> I got some atomic counter underflows in the nfs code:
>
> Mar 14 17:19:15 phoebee rpc.statd[6890]: Received erroneous SM_UNMON
> request from phoebee for 192.168.0.1 Mar 14 17:19:15 phoebee BUG: atomic
> counter underflow at:
> Mar 14 17:19:15 phoebee [<c03b51d1>] rpcauth_destroy+0x41/0x50
> Mar 14 17:19:15 phoebee [<c03afcac>] rpc_destroy_client+0x9c/0xf0
> Mar 14 17:19:15 phoebee [<c03b4698>] rpc_free+0x18/0x40
> Mar 14 17:19:15 phoebee [<c03b49ad>] rpc_release_task+0xad/0x120
> Mar 14 17:19:15 phoebee [<c03b4563>] __rpc_execute+0x2e3/0x360
> Mar 14 17:19:15 phoebee [<c03b1580>] xprt_init_autodisconnect+0x0/0xd0
> Mar 14 17:19:15 phoebee [<c012c9e0>] autoremove_wake_function+0x0/0x50
> Mar 14 17:19:15 phoebee [<c03af9e7>] rpc_create_client+0x167/0x240
> Mar 14 17:19:15 phoebee [<c012c9e0>] autoremove_wake_function+0x0/0x50
> Mar 14 17:19:15 phoebee [<c03afefa>] rpc_call_sync+0x5a/0xa0
> Mar 14 17:19:15 phoebee [<c0203874>] nsm_mon_unmon+0xb4/0xe0
> Mar 14 17:19:15 phoebee [<c0203936>] nsm_unmonitor+0x26/0x70
> Mar 14 17:19:15 phoebee [<c02007e8>] nlm_gc_hosts+0x168/0x190
> Mar 14 17:19:15 phoebee [<c0200056>] nlm_lookup_host+0x46/0x270
> Mar 14 17:19:15 phoebee [<c01fffd1>] nlmclnt_lookup_host+0x11/0x20
> Mar 14 17:19:15 phoebee [<c01ff1da>] nlmclnt_proc+0x4a/0x310
> Mar 14 17:19:15 phoebee [<c012c9e0>] autoremove_wake_function+0x0/0x50
> Mar 14 17:19:15 phoebee [<c034955e>] kernel_sendmsg+0x2e/0x40
> Mar 14 17:19:15 phoebee [<c03bb029>] xdr_sendpages+0xc9/0x270
> Mar 14 17:19:15 phoebee [<c013a11c>] mempool_free+0x4c/0xa0
> Mar 14 17:19:15 phoebee [<c03afd4b>] rpc_release_client+0x4b/0x90
> Mar 14 17:19:15 phoebee [<c03b49a6>] rpc_release_task+0xa6/0x120
> Mar 14 17:19:15 phoebee [<c03b4563>] __rpc_execute+0x2e3/0x360
> Mar 14 17:19:15 phoebee [<c012c9e0>] autoremove_wake_function+0x0/0x50
> Mar 14 17:19:15 phoebee [<c012c9e0>] autoremove_wake_function+0x0/0x50
> Mar 14 17:19:15 phoebee [<c03aff05>] rpc_call_sync+0x65/0xa0
> Mar 14 17:19:15 phoebee [<c01cbe93>] nfs3_rpc_wrapper+0x63/0x70
> Mar 14 17:19:15 phoebee [<c01cc113>] nfs3_proc_setattr+0x93/0xd0
> Mar 14 17:19:15 phoebee [<c01ca38c>] nfs_scan_commit+0x2c/0x70
> Mar 14 17:19:15 phoebee [<c01c3500>] nfs_setattr+0xd0/0x1c0
> Mar 14 17:19:15 phoebee [<c013642c>] __filemap_fdatawrite_range+0xbc/0xc0
> Mar 14 17:19:15 phoebee [<c01ca38c>] nfs_scan_commit+0x2c/0x70
> Mar 14 17:19:15 phoebee [<c01cbc6f>] nfs_commit_inode+0x3f/0xc0
> Mar 14 17:19:15 phoebee [<c01cbd44>] nfs_sync_inode+0x54/0x70
> Mar 14 17:19:15 phoebee [<c01c1e37>] do_setlk+0x77/0x170
> Mar 14 17:19:15 phoebee [<c01c1f30>] nfs_lock+0x0/0x130
> Mar 14 17:19:15 phoebee [<c016947b>] fcntl_setlk64+0x25b/0x2b0
> Mar 14 17:19:15 phoebee [<c0169e4e>] dput+0x1e/0x250
> Mar 14 17:19:15 phoebee [<c0160790>] path_release+0x10/0x60
> Mar 14 17:19:15 phoebee [<c01528a9>] sys_chown+0x49/0x50
> Mar 14 17:19:15 phoebee [<c0164e74>] sys_fcntl64+0x44/0x90
> Mar 14 17:19:15 phoebee [<c0103071>] syscall_call+0x7/0xb
> Mar 14 17:19:15 phoebee BUG: atomic counter underflow at:
> Mar 14 17:19:15 phoebee [<c03b51d1>] rpcauth_destroy+0x41/0x50
> Mar 14 17:19:15 phoebee [<c03afcac>] rpc_destroy_client+0x9c/0xf0
> Mar 14 17:19:15 phoebee [<c03b4698>] rpc_free+0x18/0x40
> Mar 14 17:19:15 phoebee [<c03b49ad>] rpc_release_task+0xad/0x120
> Mar 14 17:19:15 phoebee [<c03b4563>] __rpc_execute+0x2e3/0x360
> Mar 14 17:19:15 phoebee [<c03b1580>] xprt_init_autodisconnect+0x0/0xd0
> Mar 14 17:19:15 phoebee [<c012c9e0>] autoremove_wake_function+0x0/0x50
> Mar 14 17:19:15 phoebee [<c03af9e7>] rpc_create_client+0x167/0x240
> Mar 14 17:19:15 phoebee [<c012c9e0>] autoremove_wake_function+0x0/0x50
> Mar 14 17:19:15 phoebee [<c03afefa>] rpc_call_sync+0x5a/0xa0
> Mar 14 17:19:15 phoebee [<c0203874>] nsm_mon_unmon+0xb4/0xe0
> Mar 14 17:19:15 phoebee [<c028118f>] extract_entropy+0x4f/0xa0
> Mar 14 17:19:15 phoebee [<c02038c6>] nsm_monitor+0x26/0x70
> Mar 14 17:19:15 phoebee [<c01ffa9b>] nlmclnt_lock+0x2b/0xd0
> Mar 14 17:19:15 phoebee [<c01ff397>] nlmclnt_proc+0x207/0x310
> Mar 14 17:19:15 phoebee [<c012c9e0>] autoremove_wake_function+0x0/0x50
> Mar 14 17:19:15 phoebee [<c01c1e37>] do_setlk+0x77/0x170
> Mar 14 17:19:15 phoebee [<c01c1f30>] nfs_lock+0x0/0x130
> Mar 14 17:19:15 phoebee [<c016947b>] fcntl_setlk64+0x25b/0x2b0
> Mar 14 17:19:15 phoebee [<c0169e4e>] dput+0x1e/0x250
> Mar 14 17:19:15 phoebee [<c0160790>] path_release+0x10/0x60
> Mar 14 17:19:15 phoebee [<c01528a9>] sys_chown+0x49/0x50
> Mar 14 17:19:15 phoebee [<c0164e74>] sys_fcntl64+0x44/0x90
> Mar 14 17:19:15 phoebee [<c0103071>] syscall_call+0x7/0xb
>
>
> Regardless of the "erroneous SM_UNMON request", the atomic counter
> should not underflow ;)
>
>
> Regards,
> Martin

After some rookie debugging I think I've found the evildoer:

rpcauth_create used to have a line that inits rpc_auth->au_count to one
atomically. This line is now missing so when you release the rpc
authentication handle, the au_count underflows. Here's a fix:

Signed-off-by: Borislav Petkov <petkov@uni-muenster.de>

--- net/sunrpc/auth.c.orig 2005-03-15 22:34:58.000000000 +0100
+++ net/sunrpc/auth.c 2005-03-15 22:36:23.000000000 +0100
@@ -70,6 +70,7 @@ rpcauth_create(rpc_authflavor_t pseudofl
  auth = ops->create(clnt, pseudoflavor);
  if (!auth)
   return NULL;
+ atomic_set(&auth->au_count, 1);
  if (clnt->cl_auth)
   rpcauth_destroy(clnt->cl_auth);
  clnt->cl_auth = auth;
-
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