From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konstantin Khlebnikov Subject: Re: [PATCH v3.17 .. v3.19] lib/rhashtable: fix race between rhashtable_lookup_compare and hashtable resize Date: Tue, 30 Jun 2015 12:39:42 +0300 Message-ID: <559263DE.3060702@yandex-team.ru> References: <20150626104817.16520.77222.stgit@buzz> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit To: netdev , Eric Dumazet , Herbert Xu , Stable , David Miller , Sasha Levin Return-path: In-Reply-To: <20150626104817.16520.77222.stgit@buzz> Sender: stable-owner@vger.kernel.org List-Id: netdev.vger.kernel.org +CC Sasha Levin FYI: this patch fixes race in netlink which leads to hung in glibc function getaddrinfo() because it doesn't handle errors at all. On 26.06.2015 13:48, Konstantin Khlebnikov wrote: > Hash value passed as argument into rhashtable_lookup_compare could be > computed using different hash table than rhashtable_lookup_compare sees. > > This patch passes key into rhashtable_lookup_compare() instead of hash and > compures hash value right in place using the same table as for lookup. > > Also it adds comment for rhashtable_hashfn and rhashtable_obj_hashfn: > user must prevent concurrent insert/remove otherwise returned hash value > could be invalid. > > Signed-off-by: Konstantin Khlebnikov > Fixes: e341694e3eb5 ("netlink: Convert netlink_lookup() to use RCU protected hash table") > Link: http://lkml.kernel.org/r/20150514042151.GA5482@gondor.apana.org.au > Cc: Stable (v3.17 .. v3.19) > --- > include/linux/rhashtable.h | 2 +- > lib/rhashtable.c | 12 ++++++++---- > net/netlink/af_netlink.c | 5 +---- > 3 files changed, 10 insertions(+), 9 deletions(-) > > diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h > index fb298e9d6d3a..84056743780a 100644 > --- a/include/linux/rhashtable.h > +++ b/include/linux/rhashtable.h > @@ -108,7 +108,7 @@ int rhashtable_expand(struct rhashtable *ht, gfp_t flags); > int rhashtable_shrink(struct rhashtable *ht, gfp_t flags); > > void *rhashtable_lookup(const struct rhashtable *ht, const void *key); > -void *rhashtable_lookup_compare(const struct rhashtable *ht, u32 hash, > +void *rhashtable_lookup_compare(const struct rhashtable *ht, void *key, > bool (*compare)(void *, void *), void *arg); > > void rhashtable_destroy(const struct rhashtable *ht); > diff --git a/lib/rhashtable.c b/lib/rhashtable.c > index 624a0b7c05ef..cb22073fe687 100644 > --- a/lib/rhashtable.c > +++ b/lib/rhashtable.c > @@ -61,6 +61,8 @@ static u32 __hashfn(const struct rhashtable *ht, const void *key, > * Computes the hash value using the hash function provided in the 'hashfn' > * of struct rhashtable_params. The returned value is guaranteed to be > * smaller than the number of buckets in the hash table. > + * > + * The caller must ensure that no concurrent table mutations occur. > */ > u32 rhashtable_hashfn(const struct rhashtable *ht, const void *key, u32 len) > { > @@ -92,6 +94,8 @@ static u32 obj_hashfn(const struct rhashtable *ht, const void *ptr, u32 hsize) > * 'obj_hashfn' depending on whether the hash table is set up to work with > * a fixed length key. The returned value is guaranteed to be smaller than > * the number of buckets in the hash table. > + * > + * The caller must ensure that no concurrent table mutations occur. > */ > u32 rhashtable_obj_hashfn(const struct rhashtable *ht, void *ptr) > { > @@ -474,7 +478,7 @@ EXPORT_SYMBOL_GPL(rhashtable_lookup); > /** > * rhashtable_lookup_compare - search hash table with compare function > * @ht: hash table > - * @hash: hash value of desired entry > + * @key: pointer to key > * @compare: compare function, must return true on match > * @arg: argument passed on to compare function > * > @@ -486,14 +490,14 @@ EXPORT_SYMBOL_GPL(rhashtable_lookup); > * > * Returns the first entry on which the compare function returned true. > */ > -void *rhashtable_lookup_compare(const struct rhashtable *ht, u32 hash, > +void *rhashtable_lookup_compare(const struct rhashtable *ht, void *key, > bool (*compare)(void *, void *), void *arg) > { > const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); > struct rhash_head *he; > + u32 hash; > > - if (unlikely(hash >= tbl->size)) > - return NULL; > + hash = __hashfn(ht, key, ht->p.key_len, tbl->size); > > rht_for_each_rcu(he, tbl->buckets[hash], ht) { > if (!compare(rht_obj(ht, he), arg)) > diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c > index c0a418766f9c..c82b2e37e652 100644 > --- a/net/netlink/af_netlink.c > +++ b/net/netlink/af_netlink.c > @@ -1003,11 +1003,8 @@ static struct sock *__netlink_lookup(struct netlink_table *table, u32 portid, > .net = net, > .portid = portid, > }; > - u32 hash; > > - hash = rhashtable_hashfn(&table->hash, &portid, sizeof(portid)); > - > - return rhashtable_lookup_compare(&table->hash, hash, > + return rhashtable_lookup_compare(&table->hash, &portid, > &netlink_compare, &arg); > } > > -- Konstantin