[PATCH net 2/2] rhashtable: Do not schedule more than one rehash if we can't grow further
The current code currently only stops inserting rehashes into the chain when no resizes are currently scheduled. As long as resizes are scheduled and while inserting above the utilization watermark, more and more rehashes will be scheduled. This lead to a perfect DoS storm with thousands of rehashes scheduled which lead to thousands of spinlocks to be taken sequentially. Instead, only allow either a series of resizes or a single rehash. Drop any further rehashes and return -EBUSY. Fixes: ccd57b1bd324 (rhashtable: Add immediate rehash during insertion) Signed-off-by: Thomas Graf tg...@suug.ch Acked-by: Herbert Xu herb...@gondor.apana.org.au --- lib/rhashtable.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index f648cfd..b28df40 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -405,8 +405,8 @@ int rhashtable_insert_rehash(struct rhashtable *ht) if (rht_grow_above_75(ht, tbl)) size *= 2; - /* More than two rehashes (not resizes) detected. */ - else if (WARN_ON(old_tbl != tbl old_tbl-size == size)) + /* Do not schedule more than one rehash */ + else if (old_tbl != tbl) return -EBUSY; new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC); -- 2.3.5 -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH net 2/2] rhashtable: Do not schedule more than one rehash if we can't grow further
The current code currently only stops inserting rehashes into the chain when no resizes are currently scheduled. As long as resizes are scheduled and while inserting above the utilization watermark, more and more rehashes will be scheduled. This lead to a perfect DoS storm with thousands of rehashes scheduled which lead to thousands of spinlocks to be taken sequentially. Instead, only allow either a series of resizes or a single rehash. Drop any further rehashes and return -EBUSY. Fixes: ccd57b1bd324 (rhashtable: Add immediate rehash during insertion) Signed-off-by: Thomas Graf tg...@suug.ch --- lib/rhashtable.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 4898442..cb819ed 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -405,8 +405,8 @@ int rhashtable_insert_rehash(struct rhashtable *ht) if (rht_grow_above_75(ht, tbl)) size *= 2; - /* More than two rehashes (not resizes) detected. */ - else if (WARN_ON(old_tbl != tbl old_tbl-size == size)) + /* Do not schedule more than one rehash */ + else if (old_tbl != tbl) return -EBUSY; new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC); -- 2.3.5 -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH net 2/2] rhashtable: Do not schedule more than one rehash if we can't grow further
On Tue, Apr 21, 2015 at 02:55:35PM +0200, Thomas Graf wrote: The current code currently only stops inserting rehashes into the chain when no resizes are currently scheduled. As long as resizes are scheduled and while inserting above the utilization watermark, more and more rehashes will be scheduled. This lead to a perfect DoS storm with thousands of rehashes scheduled which lead to thousands of spinlocks to be taken sequentially. Instead, only allow either a series of resizes or a single rehash. Drop any further rehashes and return -EBUSY. Fixes: ccd57b1bd324 (rhashtable: Add immediate rehash during insertion) Signed-off-by: Thomas Graf tg...@suug.ch Acked-by: Herbert Xu herb...@gondor.apana.org.au -- Email: Herbert Xu herb...@gondor.apana.org.au Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
