From a87b9ebf1709687ff213091d0fdb4254b1564803 Mon Sep 17 00:00:00 2001 From: Thomas Graf Date: Wed, 22 Apr 2015 09:41:46 +0200 Subject: [PATCH] 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 Acked-by: Herbert Xu Signed-off-by: David S. Miller --- lib/rhashtable.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index f648cfde8520..b28df4019ade 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); -- 2.30.2