Re: [PATCH v2] brcmfmac: replace one-element array with flexible-array member

Arend Van Spriel <arend.vanspriel@xxxxxxxxxxxx> · Fri, 19 Jan 2024 07:35:52 +0100

On January 18, 2024 9:19:52 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote:

On Thu, Jan 18, 2024 at 02:53:28PM +0100, Arend van Spriel wrote:
+ Kees

On 8/3/2023 7:22 AM, Atul Raut wrote:
One-element arrays are obsolete, and flexible
array members have taken their place. So, in
struct cca_stats_n_flags, replace the one-element
array with a flexible-array member.

This fixes warnings such as:
./drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:119:6-9: 
WARNING use flexible-array member instead 
(https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)

I think this correct, but maybe Kees can give definitive answer here.

Signed-off-by: Atul Raut <rauji.raut@xxxxxxxxx>
---
drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c 
b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
index de8a2e27f49c..fff32e54833d 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
@@ -116,7 +116,7 @@ struct brcmf_dump_survey {
struct cca_stats_n_flags {
u32 msrmnt_time; /* Time for Measurement (msec) */
u32 msrmnt_done; /* flag set when measurement complete */
- char buf[1];
+ char buf[];
};
struct cca_msrmnt_query {

Normally a [1] -> [] conversion needs some details in the commit log
about why this is safe (since it runs the risk of changing sizeof(struct
cca_stats_n_flags). In this case, there's only a single user of the
struct, and nothing about its use depends on its size:

#define BRCMF_DCMD_MEDLEN       1536
...
       struct cca_stats_n_flags *results;
       char *buf;
...
       buf = kzalloc(sizeof(char) * BRCMF_DCMD_MEDLEN, GFP_KERNEL);
...
       results = (struct cca_stats_n_flags *)(buf);
...
               brcmf_parse_dump_obss(results->buf, survey);

So, the allocation size is big enough for the struct, and nothing
depends on the struct size.

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

Thanks for the confirmation.

Regards,
Arend

--
Kees Cook



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