On Wed, Oct 19, 2011 at 06:10:35AM +0200, Eric Dumazet wrote: > Le mardi 18 octobre 2011 à 17:34 -0400, Jim Sansing a écrit : > > Eric Dumazet wrote: > > > Le mardi 18 octobre 2011 à 15:08 -0400, Jim Sansing a écrit : > > > > > >> I have been working on a kernel module that registers with netfilter, > > >> and I noticed that a patch was added to nf_queue that changed the > > >> handling of return code NF_FILTER from 'do nothing' to 'free the skb'. > > >> I'm not sure which kernel version this went in, but the date of the > > >> patch is Feb, 19, 2010. > > >> > > >> Everything I have read about netfilter states that it is up to the > > >> netfilter hook to free the skb if NF_STOLEN is returned. The > > >> implications of this patch from a hook programming perspective are: > > >> > > >> 1) If the skb is used after the return from the hook, it must be cloned. > > >> 2) The original skb must not be freed. > > >> > > >> I suggest that a comment be added to include/linux/netfilter.h that says > > >> explicitly the skb will be freed if NF_STOLEN is returned. > > >> > > > > > > But its not true. Just read the code. > > > > > > If you are working on this stuff I recommend you take a look at > > > commits : > > > > > > c6675233f9015d3c0460c8aab53ed9b99d915c64 > > > (netfilter: nf_queue: reject NF_STOLEN verdicts from userspace) > > > > > > fad54440438a7c231a6ae347738423cbabc936d9 > > > (netfilter: avoid double free in nf_reinject) > > > > > > 64507fdbc29c3a622180378210ecea8659b14e40 > > > (netfilter: nf_queue: fix NF_STOLEN skb leak) > > > > > > 3bc38712e3a6e0596ccb6f8299043a826f983701 > > > ([NETFILTER]: nf_queue: handle NF_STOP and unknown verdicts in > > > nf_reinject) > > > > > > > > > > I see that fad54440438a7c231a6ae347738423cbabc936d9 (netfilter: avoid > > double free in nf_reinject) returns the switch case for NF_STOLEN back > > to the original state, but I just downloaded 3.0.4, and the skb is still > > freed. So for some versions of the kernel, the situation exists. > > Hopefully anyone who runs into it will find this thread. > > > > Hopefully netfilter guys (CCed) will sort out the problem and ask stable > submissions, if not already done. 3.0.4 is quite old :) Not done yet, sorry. I'll do it asap. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
