Fri, Oct 21, 2016 at 05:55:53PM CEST, a...@arndb.de wrote: >gcc warns about an uninitialized pointer dereference in the vlan >priority handling: > >net/core/flow_dissector.c: In function '__skb_flow_dissect': >net/core/flow_dissector.c:281:61: error: 'vlan' may be used uninitialized in >this function [-Werror=maybe-uninitialized] > >From all I can tell, this warning is about a real bug, and we >should not attempt look up the vlan header if there was >no vlan tag.
I don't see how vlan could be used uninitialized. But I understand that this is impossible for gcc to track it. Please just use uninitialized_var() > >Fixes: f6a66927692e ("flow_dissector: Get vlan priority in addition to vlan >id") >Signed-off-by: Arnd Bergmann <a...@arndb.de> >--- >I'm not sure about this one, please have a closer look at what >the original code does before applying. >--- > net/core/flow_dissector.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > >diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c >index 44e6ba9d3a6b..dd6003bf27e1 100644 >--- a/net/core/flow_dissector.c >+++ b/net/core/flow_dissector.c >@@ -245,7 +245,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb, > } > case htons(ETH_P_8021AD): > case htons(ETH_P_8021Q): { >- const struct vlan_hdr *vlan; >+ const struct vlan_hdr *vlan = NULL; > > if (skb && skb_vlan_tag_present(skb)) > proto = skb->protocol; >@@ -264,7 +264,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb, > } > > skip_vlan = true; >- if (dissector_uses_key(flow_dissector, >+ if (vlan && dissector_uses_key(flow_dissector, > FLOW_DISSECTOR_KEY_VLAN)) { > key_vlan = skb_flow_dissector_target(flow_dissector, > > FLOW_DISSECTOR_KEY_VLAN, >-- >2.9.0 >