On Tue, Nov 08, 2016 at 02:28:19PM +0100, Arnd Bergmann wrote:
> gcc correctly identified a theoretical uninitialized variable use:
>
> net/netfilter/nf_conntrack_core.c: In function 'nf_conntrack_in':
> net/netfilter/nf_conntrack_core.c:1125:14: error: 'l4proto' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>
> This could only happen when we 'goto out' before looking up l4proto,
> and then enter the retry, implying that l3proto->get_l4proto()
> returned NF_REPEAT. This does not currently get returned in any
> code path and probably won't ever happen, but is not good to
> rely on.
>
> Moving the repeat handling up a little should have the same
> behavior as today but avoids the warning by making that case
> impossible to enter.
>
> Fixes: 08733a0cb7de ("netfilter: handle NF_REPEAT from nf_conntrack_in()")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> The patch causing this is currently only in nf-next, and not yet
> in net-next.
> ---
> net/netfilter/nf_conntrack_core.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> index de4b8a75f30b..610c9de0ce18 100644
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -1337,6 +1337,8 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
> NF_CT_STAT_INC_ATOMIC(net, invalid);
> if (ret == -NF_DROP)
> NF_CT_STAT_INC_ATOMIC(net, drop);
> + if (ret == -NF_REPEAT && tmpl)
> + goto repeat;
This is my fault, I'm going to mangle this patch since 08733a0cb7de
really broke the NF_REPEAT handling. We should inconditionally jump
back to repeat if we get NF_REPEAT, no matter if the template is set
or not. I'll include a side node on this mangling.
> ret = -ret;
> goto out;
> }
> @@ -1349,10 +1351,7 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
> * closed/aborted connection. We have to go back and create a
> * fresh conntrack.
> */
I'm going to move the comment above on top of the NF_REPEAT check, so
it still keeps around as context.
BTW, the revamped patch looks like the one attached.
Thanks a lot for addressing this fallout.
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index de4b8a75f30b..e9ffe33dc0ca 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1337,6 +1337,12 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
NF_CT_STAT_INC_ATOMIC(net, invalid);
if (ret == -NF_DROP)
NF_CT_STAT_INC_ATOMIC(net, drop);
+ /* Special case: TCP tracker reports an attempt to reopen a
+ * closed/aborted connection. We have to go back and create a
+ * fresh conntrack.
+ */
+ if (ret == -NF_REPEAT)
+ goto repeat;
ret = -ret;
goto out;
}
@@ -1344,16 +1350,8 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
if (set_reply && !test_and_set_bit(IPS_SEEN_REPLY_BIT, &ct->status))
nf_conntrack_event_cache(IPCT_REPLY, ct);
out:
- if (tmpl) {
- /* Special case: TCP tracker reports an attempt to reopen a
- * closed/aborted connection. We have to go back and create a
- * fresh conntrack.
- */
- if (ret == NF_REPEAT)
- goto repeat;
- else
- nf_ct_put(tmpl);
- }
+ if (tmpl)
+ nf_ct_put(tmpl);
return ret;
}
