Re: [PATCH 2/5] sockptr: fix usize check in copy_struct_from_sockptr() for user pointers

[Aleksa Sarai]

On 2026-04-07, Stefan Metzmacher <metze@xxxxxxxxx> wrote:
> copy_struct_from_user will never hit the check_zeroed_user() call
> and will never return -E2BIG if new userspace passed new bits in a
> larger structure than the current kernel structure.
> 
> As far as I can there are no critical/related uapi changes in
> 
> - include/net/bluetooth/bluetooth.h and net/bluetooth/sco.c
>   after the use of copy_struct_from_sockptr in v6.13-rc3
> - include/uapi/linux/tcp.h and net/ipv4/tcp_ao.c
>   after the use of copy_struct_from_sockptr in v6.6-rc1
> 
> So that new callers will get the correct behavior from the start.
> 
> Fixes: 4954f17ddefc ("net/tcp: Introduce TCP_AO setsockopt()s")
> Fixes: ef84703a911f ("net/tcp: Add TCP-AO getsockopt()s")
> Fixes: faadfaba5e01 ("net/tcp: Add TCP_AO_REPAIR")
> Fixes: 3e643e4efa1e ("Bluetooth: Improve setsockopt() handling of malformed user input")
> Cc: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
> Cc: Dmitry Safonov <dima@xxxxxxxxxx>
> Cc: Francesco Ruggeri <fruggeri@xxxxxxxxxx>
> Cc: Salam Noureddine <noureddine@xxxxxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxxx>
> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> Cc: Michal Luczaj <mhal@xxxxxxx>
> Cc: David Wei <dw@xxxxxxxxxxx>
> Cc: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
> Cc: Luiz Augusto von Dentz <luiz.dentz@xxxxxxxxx>
> Cc: Marcel Holtmann <marcel@xxxxxxxxxxxx>
> Cc: Xin Long <lucien.xin@xxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
> Cc: Neal Cardwell <ncardwell@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Simon Horman <horms@xxxxxxxxxx>
> Cc: Aleksa Sarai <cyphar@xxxxxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> CC: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-bluetooth@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Stefan Metzmacher <metze@xxxxxxxxx>
> ---
>  include/linux/sockptr.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
> index 3e6c8e9d67ae..ba88f4d78c1b 100644
> --- a/include/linux/sockptr.h
> +++ b/include/linux/sockptr.h
> @@ -91,7 +91,7 @@ static inline int copy_struct_from_sockptr(void *dst, size_t ksize,
>  	size_t rest = max(ksize, usize) - size;
>  
>  	if (!sockptr_is_kernel(src))
> -		return copy_struct_from_user(dst, ksize, src.user, size);
> +		return copy_struct_from_user(dst, ksize, src.user, usize);
>  
>  	if (usize < ksize) {
>  		memset(dst + size, 0, rest);

It is a little weird that this function open-codes memchr_inv() --
check_zeroed_sockptr() exists and does the right thing. Maybe it'd be
nice to fix that too?

In any case,

Reviewed-by: Aleksa Sarai <aleksa@xxxxxxxxxxxx>

-- 
Aleksa Sarai
https://www.cyphar.com/

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