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Date: Mon, 22 Apr 2019 15:44:44 -0400 From: Sasha Levin <sashal@...nel.org> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org Cc: Davide Caratti <dcaratti@...hat.com>, "David S . Miller" <davem@...emloft.net>, Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org Subject: [PATCH AUTOSEL 4.19 36/68] net/sched: don't dereference a->goto_chain to read the chain index From: Davide Caratti <dcaratti@...hat.com> [ 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@...hat.com> Signed-off-by: David S. Miller <davem@...emloft.net> Signed-off-by: Sasha Levin (Microsoft) <sashal@...nel.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 ef8dd0db70ce..56935bf027a7 100644 --- a/include/net/tc_act/tc_gact.h +++ b/include/net/tc_act/tc_gact.h @@ -56,7 +56,7 @@ 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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