From e912b1142be8f1e2c71c71001dc992c6e5eb2ec1 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 8 Jul 2009 19:36:05 +0000 Subject: [PATCH] net: sk_prot_alloc() should not blindly overwrite memory Some sockets use SLAB_DESTROY_BY_RCU, and our RCU code correctness depends on sk->sk_nulls_node.next being always valid. A NULL value is not allowed as it might fault a lockless reader. Current sk_prot_alloc() implementation doesnt respect this hypothesis, calling kmem_cache_alloc() with __GFP_ZERO. Just call memset() around the forbidden field. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/sock.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/net/core/sock.c b/net/core/sock.c index 6354863b1c68..ba5d2116aea1 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -939,8 +939,23 @@ static struct sock *sk_prot_alloc(struct proto *prot, gfp_t priority, struct kmem_cache *slab; slab = prot->slab; - if (slab != NULL) - sk = kmem_cache_alloc(slab, priority); + if (slab != NULL) { + sk = kmem_cache_alloc(slab, priority & ~__GFP_ZERO); + if (!sk) + return sk; + if (priority & __GFP_ZERO) { + /* + * caches using SLAB_DESTROY_BY_RCU should let + * sk_node.next un-modified. Special care is taken + * when initializing object to zero. + */ + if (offsetof(struct sock, sk_node.next) != 0) + memset(sk, 0, offsetof(struct sock, sk_node.next)); + memset(&sk->sk_node.pprev, 0, + prot->obj_size - offsetof(struct sock, + sk_node.pprev)); + } + } else sk = kmalloc(prot->obj_size, priority);