From: Pavel Emelyanov Date: Mon, 14 Apr 2008 07:44:52 +0000 (-0700) Subject: [NETFILTER]: ipt_CLUSTERIP: fix race between clusterip_config_find_get and _entry_put X-Git-Tag: v2.6.25~33^2~1 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=4dee959723e2bf3a0f9343a46841cd2f0029d424;p=linux-2.6-omap-h63xx.git [NETFILTER]: ipt_CLUSTERIP: fix race between clusterip_config_find_get and _entry_put Consider we are putting a clusterip_config entry with the "entries" count == 1, and on the other CPU there's a clusterip_config_find_get in progress: CPU1: CPU2: clusterip_config_entry_put: clusterip_config_find_get: if (atomic_dec_and_test(&c->entries)) { /* true */ read_lock_bh(&clusterip_lock); c = __clusterip_config_find(clusterip); /* found - it's still in list */ ... atomic_inc(&c->entries); read_unlock_bh(&clusterip_lock); write_lock_bh(&clusterip_lock); list_del(&c->list); write_unlock_bh(&clusterip_lock); ... dev_put(c->dev); Oops! We have an entry returned by the clusterip_config_find_get, which is a) not in list b) has a stale dev pointer. The problems will happen when the CPU2 will release the entry - it will remove it from the list for the 2nd time, thus spoiling it, and will put a stale dev pointer. The fix is to make atomic_dec_and_test under the clusterip_lock. Signed-off-by: Pavel Emelyanov Signed-off-by: Patrick McHardy --- diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c index 52926c8e3cc..a12dd329e20 100644 --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c @@ -82,8 +82,8 @@ clusterip_config_put(struct clusterip_config *c) static inline void clusterip_config_entry_put(struct clusterip_config *c) { + write_lock_bh(&clusterip_lock); if (atomic_dec_and_test(&c->entries)) { - write_lock_bh(&clusterip_lock); list_del(&c->list); write_unlock_bh(&clusterip_lock); @@ -96,7 +96,9 @@ clusterip_config_entry_put(struct clusterip_config *c) #ifdef CONFIG_PROC_FS remove_proc_entry(c->pde->name, c->pde->parent); #endif + return; } + write_unlock_bh(&clusterip_lock); } static struct clusterip_config *