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svcrpc: modifying valid sunrpc cache entries is racy

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Once a sunrpc cache entry is VALID, we should be replacing it (and
allowing any concurrent users to destroy it on last put) instead of
trying to update it in place.

Otherwise someone referencing the ip_map we're modifying here could try
to use the m_client just as we're putting the last reference.

The bug should only be seen by users of the legacy nfsd interfaces.

(Thanks to Neil for suggestion to use sunrpc_invalidate.)

Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
J. Bruce Fields 2010-12-24 14:03:38 -05:00
parent 22b6dee842
commit 31f7aa65f5
1 changed files with 1 additions and 2 deletions
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3
net/sunrpc/svcauth_unix.c
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@ -401,8 +401,7 @@ struct auth_domain *auth_unix_lookup(struct net *net, struct in6_addr *addr)
return NULL;
if ((ipm->m_client->addr_changes - ipm->m_add_change) >0) {
if (test_and_set_bit(CACHE_NEGATIVE, &ipm->h.flags) == 0)
auth_domain_put(&ipm->m_client->h);
sunrpc_invalidate(&ipm->h, sn->ip_map_cache);
rv = NULL;
} else {
rv = &ipm->m_client->h;