[PATCH bpf-next] bpf: use the proper optlen when doing strncpy in bpf_getsockopt()

[PATCH bpf-next] bpf: use the proper optlen when doing strncpy in bpf_getsockopt()

[Yafang Shao]

As the last character of optval will be set with 0, so just copying
(optlen - 1) characters is enough.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 447dd1b..7a4de22 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4262,7 +4262,7 @@ static unsigned long bpf_xdp_copy(void *dst_buff, const void *src_buff,
 
 			if (!icsk->icsk_ca_ops || optlen <= 1)
 				goto err_clear;
-			strncpy(optval, icsk->icsk_ca_ops->name, optlen);
+			strncpy(optval, icsk->icsk_ca_ops->name, optlen - 1);
 			optval[optlen - 1] = 0;
 			break;
 		case TCP_SAVED_SYN:
-- 
1.8.3.1

Re: [PATCH bpf-next] bpf: use the proper optlen when doing strncpy in bpf_getsockopt()

[Martin Lau]

On Sat, Jan 19, 2019 at 02:20:52PM +0800, Yafang Shao wrote:
> As the last character of optval will be set with 0, so just copying
> (optlen - 1) characters is enough.
I am not sure this optimization is needed but I think it will
make it more consistent with the bpf_setsockopt() above.

Acked-by: Martin KaFai Lau <kafai@fb.com>

Cc: Lawrence Brakmo <brakmo@fb.com>

> 
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>  net/core/filter.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 447dd1b..7a4de22 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4262,7 +4262,7 @@ static unsigned long bpf_xdp_copy(void *dst_buff, const void *src_buff,
>  
>  			if (!icsk->icsk_ca_ops || optlen <= 1)
>  				goto err_clear;
> -			strncpy(optval, icsk->icsk_ca_ops->name, optlen);
> +			strncpy(optval, icsk->icsk_ca_ops->name, optlen - 1);
>  			optval[optlen - 1] = 0;
>  			break;
>  		case TCP_SAVED_SYN:
> -- 
> 1.8.3.1
> 

Re: [PATCH bpf-next] bpf: use the proper optlen when doing strncpy in bpf_getsockopt()

[Lawrence Brakmo]

On 1/22/19, 10:05 AM, "Martin Lau" <kafai@fb.com> wrote:

    On Sat, Jan 19, 2019 at 02:20:52PM +0800, Yafang Shao wrote:
    > As the last character of optval will be set with 0, so just copying
    > (optlen - 1) characters is enough.
    I am not sure this optimization is needed but I think it will
    make it more consistent with the bpf_setsockopt() above.
    
    Acked-by: Martin KaFai Lau <kafai@fb.com>
    
    Cc: Lawrence Brakmo <brakmo@fb.com>

Acked-by: Lawrence Brakmo <brakmo@fb.com>
    
    > 
    > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
    > ---
    >  net/core/filter.c | 2 +-
    >  1 file changed, 1 insertion(+), 1 deletion(-)
    > 
    > diff --git a/net/core/filter.c b/net/core/filter.c
    > index 447dd1b..7a4de22 100644
    > --- a/net/core/filter.c
    > +++ b/net/core/filter.c
    > @@ -4262,7 +4262,7 @@ static unsigned long bpf_xdp_copy(void *dst_buff, const void *src_buff,
    >  
    >  			if (!icsk->icsk_ca_ops || optlen <= 1)
    >  				goto err_clear;
    > -			strncpy(optval, icsk->icsk_ca_ops->name, optlen);
    > +			strncpy(optval, icsk->icsk_ca_ops->name, optlen - 1);
    >  			optval[optlen - 1] = 0;
    >  			break;
    >  		case TCP_SAVED_SYN:
    > -- 
    > 1.8.3.1
    > 
    

Re: [PATCH bpf-next] bpf: use the proper optlen when doing strncpy in bpf_getsockopt()

[Daniel Borkmann]

On 01/22/2019 07:04 PM, Martin Lau wrote:
> On Sat, Jan 19, 2019 at 02:20:52PM +0800, Yafang Shao wrote:
>> As the last character of optval will be set with 0, so just copying
>> (optlen - 1) characters is enough.
> I am not sure this optimization is needed but I think it will

Yeah, it's totally fine as is.