linux-kernel - Re: [PATCH] bpf: decrease usercnt if bpf_map_new_fd() fails in bpf_map_get_fd_by

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Message-ID: <564058e0-1432-676e-2f83-c8694911d8e5@iogearbox.net>
Date:   Tue, 26 Feb 2019 15:44:39 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     zerons <sironhide0null@...il.com>, ast@...nel.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bpf: decrease usercnt if bpf_map_new_fd() fails in
 bpf_map_get_fd_by_id()

On 02/26/2019 03:15 PM, zerons wrote:
> [ Upstream commit c91951f15978f1a0c6b65f063d30f7ea7bc6fb42 ]

Thanks for the fix! What do you mean by "upstream commit" above in this context?

> In bpf/syscall.c, bpf_map_get_fd_by_id() use bpf_map_inc_not_zero() to increase
> the refcount, both map->refcnt and map->usercnt. Then, if bpf_map_new_fd() fails,
> should handle map->usercnt too.
> 
> Signed-off-by: zerons <sironhide0null@...il.com>
> ---
>  kernel/bpf/syscall.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index cf5040f..db1ed12 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -1966,7 +1966,7 @@ static int bpf_map_get_fd_by_id(const union bpf_attr *attr)
> 
>  	fd = bpf_map_new_fd(map, f_flags);
>  	if (fd < 0)
> -		bpf_map_put(map);
> +		bpf_map_put_with_uref(map);
> 
>  	return fd;
>  }
> --
> 2.7.4
>