[SRU][J:linux-bluefield][PATCH v4 09/10] net/sched: clear actions pointer in miss cookie init fail

[William Tu]

From: Pedro Tammela <pctammela at mojatatu.com>

BugLink: https://bugs.launchpad.net/bugs/2012571

Palash reports a UAF when using a modified version of syzkaller[1].

When 'tcf_exts_miss_cookie_base_alloc()' fails in 'tcf_exts_init_ex()'
a call to 'tcf_exts_destroy()' is made to free up the tcf_exts
resources.
In flower, a call to '__fl_put()' when 'tcf_exts_init_ex()' fails is made;
Then calling 'tcf_exts_destroy()', which triggers an UAF since the
already freed tcf_exts action pointer is lingering in the struct.

Before the offending patch, this was not an issue since there was no
case where the tcf_exts action pointer could linger. Therefore, restore
the old semantic by clearing the action pointer in case of a failure to
initialize the miss_cookie.

[1] https://github.com/cmu-pasta/linux-kernel-enriched-corpus

v1->v2: Fix compilation on configs without tc actions (kernel test robot)

Fixes: 80cd22c35c90 ("net/sched: cls_api: Support hardware miss to tc action")
Reported-by: Palash Oswal <oswalpalash at gmail.com>
Acked-by: Jamal Hadi Salim <jhs at mojatatu.com>
Signed-off-by: Pedro Tammela <pctammela at mojatatu.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit 338469d677e5d426f5ada88761f16f6d2c7c1981)
Signed-off-by: William Tu <witu at nvidia.com>
---
 net/sched/cls_api.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 9848eb41ec08..c5b2a45abe18 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -3202,6 +3202,9 @@ int tcf_exts_init_ex(struct tcf_exts *exts, struct net *net, int action,
 
 err_miss_alloc:
 	tcf_exts_destroy(exts);
+#ifdef CONFIG_NET_CLS_ACT
+	exts->actions = NULL;
+#endif
 	return err;
 }
 EXPORT_SYMBOL(tcf_exts_init_ex);
-- 
2.34.1