[PATCH] net: mac80211: cfg: Initialize cnt before accessing elem

[PATCH] net: mac80211: cfg: Initialize cnt before accessing elem

[Haoyu Li]

With the new __counted_by annocation in cfg80211_rnr_elems, the "cnt"
struct member must be set before accessing the "elem" array. Failing to
do so will trigger a runtime warning when enabling CONFIG_UBSAN_BOUNDS
and CONFIG_FORTIFY_SOURCE.

Fixes: 7b6d7087031b ("wifi: cfg80211: Annotate struct cfg80211_rnr_elems with __counted_by")
Signed-off-by: Haoyu Li <lihaoyu499@gmail.com>
---
 net/mac80211/cfg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 61a824ec33da..6936b1303e81 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1105,13 +1105,13 @@ ieee80211_copy_rnr_beacon(u8 *pos, struct cfg80211_rnr_elems *dst,
 {
 	int i, offset = 0;
 
+	dst->cnt = src->cnt;
 	for (i = 0; i < src->cnt; i++) {
 		memcpy(pos + offset, src->elem[i].data, src->elem[i].len);
 		dst->elem[i].len = src->elem[i].len;
 		dst->elem[i].data = pos + offset;
 		offset += dst->elem[i].len;
 	}
-	dst->cnt = src->cnt;
 
 	return offset;
 }
-- 
2.34.1

Re: [PATCH] net: mac80211: cfg: Initialize cnt before accessing elem

[Gustavo A. R. Silva]

On 23/11/24 11:08, Haoyu Li wrote:
> With the new __counted_by annocation in cfg80211_rnr_elems, the "cnt"
> struct member must be set before accessing the "elem" array. Failing to
> do so will trigger a runtime warning when enabling CONFIG_UBSAN_BOUNDS
> and CONFIG_FORTIFY_SOURCE.
> 

Nice catch. :)

> Fixes: 7b6d7087031b ("wifi: cfg80211: Annotate struct cfg80211_rnr_elems with __counted_by")

This should be Cc'd to stable:

Cc: stable@vger.kernel.org

> Signed-off-by: Haoyu Li <lihaoyu499@gmail.com>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
-Gustavo

> ---
>   net/mac80211/cfg.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
> index 61a824ec33da..6936b1303e81 100644
> --- a/net/mac80211/cfg.c
> +++ b/net/mac80211/cfg.c
> @@ -1105,13 +1105,13 @@ ieee80211_copy_rnr_beacon(u8 *pos, struct cfg80211_rnr_elems *dst,
>   {
>   	int i, offset = 0;
>   
> +	dst->cnt = src->cnt;
>   	for (i = 0; i < src->cnt; i++) {
>   		memcpy(pos + offset, src->elem[i].data, src->elem[i].len);
>   		dst->elem[i].len = src->elem[i].len;
>   		dst->elem[i].data = pos + offset;
>   		offset += dst->elem[i].len;
>   	}
> -	dst->cnt = src->cnt;
>   
>   	return offset;
>   }