[PATCH] net: sockmap: Don't call bpf_prog_put() on NULL pointer

From: Alex Dewar
Date: Mon Oct 12 2020 - 13:10:41 EST


If bpf_prog_inc_not_zero() fails for skb_parser, then bpf_prog_put() is
called unconditionally on skb_verdict, even though it may be NULL. Fix
and tidy up error path.

Addresses-Coverity-ID: 1497799: Null pointer dereferences (FORWARD_NULL)
Fixes: 743df8b7749f ("bpf, sockmap: Check skb_verdict and skb_parser programs explicitly")
Signed-off-by: Alex Dewar <alex.dewar90@xxxxxxxxx>
---
net/core/sock_map.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index df09c39a4dd2..a73ccce54423 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -238,17 +238,18 @@ static int sock_map_link(struct bpf_map *map, struct sk_psock_progs *progs,
int ret;

skb_verdict = READ_ONCE(progs->skb_verdict);
- skb_parser = READ_ONCE(progs->skb_parser);
if (skb_verdict) {
skb_verdict = bpf_prog_inc_not_zero(skb_verdict);
if (IS_ERR(skb_verdict))
return PTR_ERR(skb_verdict);
}
+
+ skb_parser = READ_ONCE(progs->skb_parser);
if (skb_parser) {
skb_parser = bpf_prog_inc_not_zero(skb_parser);
if (IS_ERR(skb_parser)) {
- bpf_prog_put(skb_verdict);
- return PTR_ERR(skb_parser);
+ ret = PTR_ERR(skb_parser);
+ goto out_put_skb_verdict;
}
}

@@ -257,7 +258,7 @@ static int sock_map_link(struct bpf_map *map, struct sk_psock_progs *progs,
msg_parser = bpf_prog_inc_not_zero(msg_parser);
if (IS_ERR(msg_parser)) {
ret = PTR_ERR(msg_parser);
- goto out;
+ goto out_put_skb_parser;
}
}

@@ -311,11 +312,12 @@ static int sock_map_link(struct bpf_map *map, struct sk_psock_progs *progs,
out_progs:
if (msg_parser)
bpf_prog_put(msg_parser);
-out:
- if (skb_verdict)
- bpf_prog_put(skb_verdict);
+out_put_skb_parser:
if (skb_parser)
bpf_prog_put(skb_parser);
+out_put_skb_verdict:
+ if (skb_verdict)
+ bpf_prog_put(skb_verdict);
return ret;
}

--
2.28.0