netdev - [PATCH iproute2] tc: fix segmentation fault on gact action

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Date:   Tue,  1 Oct 2019 12:32:17 +0200
From:   Andrea Claudi <aclaudi@...hat.com>
To:     netdev@...r.kernel.org
Cc:     stephen@...workplumber.org, dsahern@...il.com
Subject: [PATCH iproute2] tc: fix segmentation fault on gact action

tc segfaults if gact action is used without action or index:

$ ip link add type dummy
$ tc actions add action pipe index 1
$ tc filter add dev dummy0 parent ffff: protocol ip \
  pref 10 u32 match ip src 127.0.0.2 flowid 1:10 action gact
Segmentation fault

We expect tc to fail gracefully with an error message.

This happens if gact is the last argument of the incomplete
command. In this case the "gact" action is parsed, the macro
NEXT_ARG_FWD() is executed and the next matches() crashes
because of null argv pointer.

To avoid this, simply use NEXT_ARG() instead.

With this change in place:

$ ip link add type dummy
$ tc actions add action pipe index 1
$ tc filter add dev dummy0 parent ffff: protocol ip \
  pref 10 u32 match ip src 127.0.0.2 flowid 1:10 action gact
Command line is not complete. Try option "help"

Fixes: fa4958897314 ("tc: Fix binding of gact action by index.")
Reported-by: Davide Caratti <dcaratti@...hat.com>
Signed-off-by: Andrea Claudi <aclaudi@...hat.com>
---
 tc/m_gact.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tc/m_gact.c b/tc/m_gact.c
index dca2a2f9692fd..b06e8ee95818f 100644
--- a/tc/m_gact.c
+++ b/tc/m_gact.c
@@ -87,7 +87,7 @@ parse_gact(struct action_util *a, int *argc_p, char ***argv_p,
 		return -1;

 	if (!matches(*argv, "gact"))
-		NEXT_ARG_FWD();
+		NEXT_ARG();
 	/* we're binding existing gact action to filter by index. */
 	if (!matches(*argv, "index"))
 		goto skip_args;
-- 
2.21.0