netdev - Re: [PATCH v1 net-next] socket: Print pf->create() when it does not clear sock->sk on failure.

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Message-ID: <CANn89iLEvu-bkrDWZnzG66vcbQbb2NS=U0XqH-iwa=ONE3tiQA@mail.gmail.com>
Date: Wed, 23 Oct 2024 21:45:26 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Ignat Korchagin <ignat@...udflare.com>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v1 net-next] socket: Print pf->create() when it does not
 clear sock->sk on failure.

On Wed, Oct 23, 2024 at 9:18 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> I suggested to put DEBUG_NET_WARN_ON_ONCE() in __sock_create() to
> catch possible use-after-free.
>
> But the warning itself was not useful because our interest is in
> the callee than the caller.
>
> Let's define DEBUG_NET_WARN_ONCE() and print the name of pf->create()
> and the socket identifier.
>
> While at it, we enclose DEBUG_NET_WARN_ON_ONCE() in parentheses too
> to avoid a checkpatch error.
>
> Note that %pf or %pF were obsoleted and later removed as per comment
> in lib/vsprintf.c.
>
> Link: https://lore.kernel.org/netdev/202410231427.633734b3-lkp@intel.com/
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---
>  include/net/net_debug.h | 4 +++-
>  net/socket.c            | 4 +++-
>  2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/include/net/net_debug.h b/include/net/net_debug.h
> index 1e74684cbbdb..9fecb1496be3 100644
> --- a/include/net/net_debug.h
> +++ b/include/net/net_debug.h
> @@ -149,9 +149,11 @@ do {                                                               \
>
>
>  #if defined(CONFIG_DEBUG_NET)
> -#define DEBUG_NET_WARN_ON_ONCE(cond) (void)WARN_ON_ONCE(cond)
> +#define DEBUG_NET_WARN_ON_ONCE(cond) ((void)WARN_ON_ONCE(cond))
> +#define DEBUG_NET_WARN_ONCE(cond, format...) ((void)WARN_ONCE(cond, format))
>  #else
>  #define DEBUG_NET_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond)
> +#define DEBUG_NET_WARN_ONCE(cond, format...) BUILD_BUG_ON_INVALID(cond)
>  #endif
>
>  #endif /* _LINUX_NET_DEBUG_H */
> diff --git a/net/socket.c b/net/socket.c
> index 9a8e4452b9b2..da00db3824e3 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -1578,7 +1578,9 @@ int __sock_create(struct net *net, int family, int type, int protocol,
>                 /* ->create should release the allocated sock->sk object on error
>                  * and make sure sock->sk is set to NULL to avoid use-after-free
>                  */
> -               DEBUG_NET_WARN_ON_ONCE(sock->sk);
> +               DEBUG_NET_WARN_ONCE(sock->sk,
> +                                   "%pS must clear sock->sk on failure, family: %d, type: %d, protocol: %d\n",

%ps would be more appropriate, the offset should be zero, no need to
display a full 'symbol+0x0/0x<size>'