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Message-ID: <20231113095333.GM705326@kernel.org>
Date: Mon, 13 Nov 2023 09:53:33 +0000
From: Simon Horman <horms@...nel.org>
To: Gal Pressman <gal@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
Vlad Buslov <vladbu@...dia.com>
Subject: Re: [PATCH net] net: Fix undefined behavior in netdev name allocation
On Mon, Nov 13, 2023 at 10:35:44AM +0200, Gal Pressman wrote:
> Cited commit removed the strscpy() call and kept the snprintf() only.
>
> When allocating a netdev, 'res' and 'name' pointers are equal, but
> according to POSIX, if copying takes place between objects that overlap
> as a result of a call to sprintf() or snprintf(), the results are
> undefined.
>
> Add back the strscpy() and use 'buf' as an intermediate buffer.
>
> Fixes: 9a810468126c ("net: reduce indentation of __dev_alloc_name()")
Hi Gal,
perhaps my eyes are deceiving me, but I wonder if this fixes the following:
7ad17b04dc7b ("net: trust the bitmap in __dev_alloc_name()")
> Cc: Jakub Kicinski <kuba@...nel.org>
> Reviewed-by: Vlad Buslov <vladbu@...dia.com>
> Signed-off-by: Gal Pressman <gal@...dia.com>
> ---
> net/core/dev.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 0d548431f3fa..af53f6d838ce 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -1119,7 +1119,9 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
> if (i == max_netdevices)
> return -ENFILE;
>
> - snprintf(res, IFNAMSIZ, name, i);
> + /* 'res' and 'name' could overlap, use 'buf' as an intermediate buffer */
> + strscpy(buf, name, IFNAMSIZ);
> + snprintf(res, IFNAMSIZ, buf, i);
> return i;
> }
>
> --
> 2.40.1
>
>
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