Messages in this thread | | | Subject | PROBLEM with summary: Re: [PATCH] netfilter: per netns nf_conntrack_cachep | From | Jon Masters <> | Date | Tue, 02 Feb 2010 11:58:23 -0500 |
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On Tue, 2010-02-02 at 11:46 -0500, Jon Masters wrote: > On Tue, 2010-02-02 at 06:35 -0500, Jon Masters wrote: > > > I think there's something more fundamental going on here. > > What happens is the conntrack code attempts to free > nf_conntrack_untracked back into the SL[U]B cache from which it > allocates other ct's. There's just one problem...that's a static struct > not from the cache. So, this is why we end up with the SLAB being > corrupted and the address immediately following the > nf_conntrack_untracked being corrupted. > > I shoved some debug comments into the destroy code to see if we were > trying to free nf_conntrack_untracked, and bingo. I have shoved a panic > in there now, will send you a backtrace.
So we attach after starting a VM due to icmpv6_error setting the ct in some incoming skb to the "untracked" catchall one. Then we panic when I force a panic if attempting to free the nf_conntrack_untracked static struct with this backtrace:
#5 0xffffffff81455884 in panic ( fmt=0xffffffff81ec51e0 "JCM: nf_conntrack_destroy: trying to destroy nf_conntrack_untracked!\n") at kernel/panic.c:73 #6 0xffffffff813d266c in nf_conntrack_destroy (nfct=<value optimized out>) at net/netfilter/core.c:244 #7 0xffffffff813abd97 in nf_conntrack_put (skb=0xffff880223b8b700) at include/linux/skbuff.h:1924 #8 skb_release_head_state (skb=0xffff880223b8b700) at net/core/skbuff.c:402 #9 0xffffffff813abaf9 in skb_release_all (skb=0xffff880223b8b700) at net/core/skbuff.c:420 #10 __kfree_skb (skb=0xffff880223b8b700) at net/core/skbuff.c:435 #11 0xffffffff813abbfe in kfree_skb (skb=0xffff880223b8b700) at net/core/skbuff.c:456
Could you please add (or recommend for me to test) some logic to catch attempts to free the nf_conntrack_untracked and prevent it? Also, maybe in the init_net code you could remove the re-initialization of the untracked conntrack each time a namespace is created?
Thanks!
Jon.
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