Re: [PATCH] flow_dissector: avoid uninitialized variable access
From: Jiri Pirko <jiri@resnulli.us>
Date: 2016-10-21 16:31:24
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Fri, Oct 21, 2016 at 05:55:53PM CEST, arnd@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()
quoted hunk ↗ jump to hunk
Fixes: f6a66927692e ("flow_dissector: Get vlan priority in addition to vlan id") Signed-off-by: Arnd Bergmann <arnd@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