From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BC85F1EF1D for ; Thu, 3 Jul 2025 16:14:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751559268; cv=none; b=uhPS+lN2DwXlwmIcUBGrT1tTFXFOfchmvXvv5uuMDR9WxXz08FPrMZkF9i/vwH2EHLx1fQIsNr/DmqTANsQMIuGD3IQ9WYDfosokahu4rvAwRgoWz7r+362R4Ut2FUXSCxCIuQ6Cw9Z5ynz+1mAxiAl1V6srxhmgibo0GToKUh4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751559268; c=relaxed/simple; bh=PpuNOz20PExVvuUMx+Y9esXMMhGEbMJsedc5HUA8aPo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OIQJpkEzGk+EZ0P9ILy6rK3zq35P+/1T+SCLnvVahEuM2ufH6rWjW7BnO/ZSfhOAKgHVoMYj3OfskP2kqtHGPTzbenuMItUtp4gW32FCOx3/Av9dKKvkQpWNGrUZLK4cz/A+I467bTWUOU9aU7ILJqlIFY2WIUHdOonGlmIrINM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=a8gsKSM2; arc=none smtp.client-ip=95.215.58.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="a8gsKSM2" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1751559264; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RjsWgbXGX7RbaYX+gdvDlZSlsMmT+hKRuaCsvLWPrJo=; b=a8gsKSM2BLripXrjCuby3gGqtuZwn3AkGMLZveOG4DHWQmOwcgevJPhlQuIig1trDAs7LH K1RCdFxXzHxN5BASbGdZXX2hztbahbvQ3zZZCeOr/5xWK9dzaf4m+xVtP/Pg0WigybHqlW Waqrou+24uenLQ+3aC4JYUGMnTgqX20= Date: Thu, 3 Jul 2025 09:14:15 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next] bpf: Clean code with bpf_copy_to_user Content-Language: en-GB To: Tao Chen , ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250703124336.672416-1-chen.dylane@linux.dev> <9447cc50-03be-4eba-809d-f9e3381654fa@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <9447cc50-03be-4eba-809d-f9e3381654fa@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 7/3/25 9:03 AM, Tao Chen wrote: > 在 2025/7/3 23:35, Yonghong Song 写道: >> >> >> On 7/3/25 5:43 AM, Tao Chen wrote: >>> No logic change, just use bpf_copy_to_user to clean code. >>> >>> Signed-off-by: Tao Chen >>> --- >>>   kernel/bpf/syscall.c | 17 +++-------------- >>>   1 file changed, 3 insertions(+), 14 deletions(-) >>> >>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c >>> index e6eea594f1c..ca152d36312 100644 >>> --- a/kernel/bpf/syscall.c >>> +++ b/kernel/bpf/syscall.c >>> @@ -5208,21 +5208,10 @@ static int bpf_task_fd_query_copy(const >>> union bpf_attr *attr, >>>               if (put_user(zero, ubuf)) >>>                   return -EFAULT; >>> -        } else if (input_len >= len + 1) { >>> -            /* ubuf can hold the string with NULL terminator */ >>> -            if (copy_to_user(ubuf, buf, len + 1)) >>> -                return -EFAULT; >>>           } else { >>> -            /* ubuf cannot hold the string with NULL terminator, >>> -             * do a partial copy with NULL terminator. >>> -             */ >>> -            char zero = '\0'; >>> - >>> -            err = -ENOSPC; >>> -            if (copy_to_user(ubuf, buf, input_len - 1)) >>> -                return -EFAULT; >>> -            if (put_user(zero, ubuf + input_len - 1)) >>> -                return -EFAULT; >>> +            err = bpf_copy_to_user(ubuf, buf, input_len, len); >>> +            if (err) >>> +                return err; >>>           } >>>       } >> >> Actually, there is a return value change with this patch. >> bpf_copy_to_user() return returns -ENOSPC while the original >> implementation may return -EFAULT due to following code. >> >>          if (put_user(prog_id, &uattr->task_fd_query.prog_id) || >>              put_user(fd_type, &uattr->task_fd_query.fd_type) || >>              put_user(probe_offset, >> &uattr->task_fd_query.probe_offset) || >>              put_user(probe_addr, &uattr->task_fd_query.probe_addr)) >>                  return -EFAULT; >> >>          return err; >> > > You are right, maybe we can just use: >     err = bpf_copy_to_user(ubuf, buf, input_len, len); > and no return check > or move these put_user code to the front. Maybe do the following? err = bpf_copy_to_user(ubuf, buf, input_len, len); if (err && err != -ENOSPC) return err;