[PATCHSET] Fix and add -Werror=strict-overflow -Wstrict-overflow=2

[Volker Lendecke]

On Thu, Dec 07, 2017 at 08:37:15PM +0100, Andreas Schneider via samba-technical wrote:
> From 9b5684f9acac4c4ff0136c0ef9663d8f9f4c28bf Mon Sep 17 00:00:00 2001
> From: Andreas Schneider <asn at samba.org>
> Date: Thu, 26 Oct 2017 09:43:56 +0200
> Subject: [PATCH 42/42] s3:glock: Add sanity check in g_lock_parse()
> 
> Signed-off-by: Andreas Schneider <asn at samba.org>
> ---
>  source3/lib/g_lock.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/source3/lib/g_lock.c b/source3/lib/g_lock.c
> index c5d66e3855e..ea2d7717ce5 100644
> --- a/source3/lib/g_lock.c
> +++ b/source3/lib/g_lock.c
> @@ -81,6 +81,9 @@ static bool g_lock_parse(uint8_t *buf, size_t buflen, struct g_lock *lck)
>  	buf += sizeof(uint32_t);
>  	buflen -= sizeof(uint32_t);
>  	data_ofs = found_recs * G_LOCK_REC_LENGTH;
> +	if (data_ofs >= buflen) {
> +		return false;
> +	}

Can we better fix this by moving the

        if (found_recs > buflen/G_LOCK_REC_LENGTH) {
                return false;
        }

sequence to after the buflen-=sizeof(uint32_t)?

I thought that overflow in multiplication is much better caught by
testing the reverse operation before the multiplication is done.

Volker

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