| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.14 30/49] net/sched: dont dereference a->goto_chain to read the chain index | Date | Thu, 2 May 2019 17:21:07 +0200 |
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[ Upstream commit fe384e2fa36ca084a456fd30558cccc75b4b3fbd ]
callers of tcf_gact_goto_chain_index() can potentially read an old value of the chain index, or even dereference a NULL 'goto_chain' pointer, because 'goto_chain' and 'tcfa_action' are read in the traffic path without caring of concurrent write in the control path. The most recent value of chain index can be read also from a->tcfa_action (it's encoded there together with TC_ACT_GOTO_CHAIN bits), so we don't really need to dereference 'goto_chain': just read the chain id from the control action.
Fixes: e457d86ada27 ("net: sched: add couple of goto_chain helpers") Signed-off-by: Davide Caratti <dcaratti@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org> --- include/net/tc_act/tc_gact.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/net/tc_act/tc_gact.h b/include/net/tc_act/tc_gact.h index e82d93346b63..bb74ea83d57d 100644 --- a/include/net/tc_act/tc_gact.h +++ b/include/net/tc_act/tc_gact.h @@ -51,7 +51,7 @@ static inline bool is_tcf_gact_goto_chain(const struct tc_action *a) static inline u32 tcf_gact_goto_chain_index(const struct tc_action *a) { - return a->goto_chain->index; + return READ_ONCE(a->tcfa_action) & TC_ACT_EXT_VAL_MASK; } #endif /* __NET_TC_GACT_H */ -- 2.19.1
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