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| author | Chuck Lever <chuck.lever@oracle.com> | 2013-10-17 18:14:10 (GMT) |
|---|---|---|
| committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2013-10-28 19:31:55 (GMT) |
| commit | 0625c2dd6ae32a221871ffc04bb752216b823001 (patch) | |
| tree | ade4401e23b075b947ca9d5453d2b538f37203a3 /fs/nfs | |
| parent | cd3fadece2b97462583500371a3eb9b091c49603 (diff) | |
| download | linux-0625c2dd6ae32a221871ffc04bb752216b823001.tar.xz | |
NFS: Fix possible endless state recovery wait
In nfs4_wait_clnt_recover(), hold a reference to the clp being
waited on. The state manager can reduce clp->cl_count to 1, in
which case the nfs_put_client() in nfs4_run_state_manager() can
free *clp before wait_on_bit() returns and allows
nfs4_wait_clnt_recover() to run again.
The behavior at that point is non-deterministic. If the waited-on
bit still happens to be zero, wait_on_bit() will wake the waiter as
expected. If the bit is set again (say, if the memory was poisoned
when freed) wait_on_bit() can leave the waiter asleep.
This is a narrow fix which ensures the safety of accessing *clp in
nfs4_wait_clnt_recover(), but does not address the continued use
of a possibly freed *clp after nfs4_wait_clnt_recover() returns
(see nfs_end_delegation_return(), for example).
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/nfs')
| -rw-r--r-- | fs/nfs/nfs4state.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 62c08bf..452f4c8 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -1255,14 +1255,16 @@ int nfs4_wait_clnt_recover(struct nfs_client *clp) might_sleep(); + atomic_inc(&clp->cl_count); res = wait_on_bit(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING, nfs_wait_bit_killable, TASK_KILLABLE); if (res) - return res; - + goto out; if (clp->cl_cons_state < 0) - return clp->cl_cons_state; - return 0; + res = clp->cl_cons_state; +out: + nfs_put_client(clp); + return res; } int nfs4_client_recover_expired_lease(struct nfs_client *clp) |