From d1fe19444d82e399e38c1594c71b850eca8e9de0 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 23 Jul 2015 12:05:37 +0200 Subject: [PATCH] inet: frag: don't re-use chainlist for evictor commit 65ba1f1ec0eff ("inet: frags: fix a race between inet_evict_bucket and inet_frag_kill") describes the bug, but the fix doesn't work reliably. Problem is that ->flags member can be set on other cpu without chainlock being held by that task, i.e. the RMW-Cycle can clear INET_FRAG_EVICTED bit after we put the element on the evictor private list. We can crash when walking the 'private' evictor list since an element can be deleted from list underneath the evictor. Join work with Nikolay Alexandrov. Fixes: b13d3cbfb8e8 ("inet: frag: move eviction of queues to work queue") Reported-by: Johan Schuijt Tested-by: Frank Schreuder Signed-off-by: Nikolay Alexandrov Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- include/net/inet_frag.h | 2 ++ net/ipv4/inet_fragment.c | 8 +++----- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h index e1300b3dd597..56a3a5685f76 100644 --- a/include/net/inet_frag.h +++ b/include/net/inet_frag.h @@ -45,6 +45,7 @@ enum { * @flags: fragment queue flags * @max_size: maximum received fragment size * @net: namespace that this frag belongs to + * @list_evictor: list of queues to forcefully evict (e.g. due to low memory) */ struct inet_frag_queue { spinlock_t lock; @@ -59,6 +60,7 @@ struct inet_frag_queue { __u8 flags; u16 max_size; struct netns_frags *net; + struct hlist_node list_evictor; }; #define INETFRAGS_HASHSZ 1024 diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c index 5e346a082e5f..172234864fec 100644 --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -151,14 +151,13 @@ evict_again: } fq->flags |= INET_FRAG_EVICTED; - hlist_del(&fq->list); - hlist_add_head(&fq->list, &expired); + hlist_add_head(&fq->list_evictor, &expired); ++evicted; } spin_unlock(&hb->chain_lock); - hlist_for_each_entry_safe(fq, n, &expired, list) + hlist_for_each_entry_safe(fq, n, &expired, list_evictor) f->frag_expire((unsigned long) fq); return evicted; @@ -284,8 +283,7 @@ static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f) struct inet_frag_bucket *hb; hb = get_frag_bucket_locked(fq, f); - if (!(fq->flags & INET_FRAG_EVICTED)) - hlist_del(&fq->list); + hlist_del(&fq->list); spin_unlock(&hb->chain_lock); }