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@xxxxxxxxxx> --- fs/nfs/nfs4state.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 6daa064..1a3cb26 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) -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
