netdev - [PATCH bpf-next] netdevsim: fix overflow on the error path

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Date:   Fri, 26 Jan 2018 19:50:00 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     daniel@...earbox.net, alexei.starovoitov@...il.com
Cc:     dan.carpenter@...cle.com, netdev@...r.kernel.org,
        oss-drivers@...ronome.com,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH bpf-next] netdevsim: fix overflow on the error path

Undo loop condition on the error path would cause the i counter
to go below zero, if allocation failure happened with the first
(i.e. 0th) element of the array.

Fixes: 395cacb5f1a0 ("netdevsim: bpf: support fake map offload")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
---
 drivers/net/netdevsim/bpf.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/netdevsim/bpf.c b/drivers/net/netdevsim/bpf.c
index de73c1ff0939..75c25306d234 100644
--- a/drivers/net/netdevsim/bpf.c
+++ b/drivers/net/netdevsim/bpf.c
@@ -480,8 +480,7 @@ static int
 nsim_bpf_map_alloc(struct netdevsim *ns, struct bpf_offloaded_map *offmap)
 {
 	struct nsim_bpf_bound_map *nmap;
-	unsigned int i;
-	int err;
+	int i, err;
 
 	if (WARN_ON(offmap->map.map_type != BPF_MAP_TYPE_ARRAY &&
 		    offmap->map.map_type != BPF_MAP_TYPE_HASH))
@@ -518,7 +517,7 @@ nsim_bpf_map_alloc(struct netdevsim *ns, struct bpf_offloaded_map *offmap)
 	return 0;
 
 err_free:
-	while (--i) {
+	while (--i >= 0) {
 		kfree(nmap->entry[i].key);
 		kfree(nmap->entry[i].value);
 	}
-- 
2.15.1