From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 649AF416879; Fri, 24 Jul 2026 15:55:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784908503; cv=none; b=tBsi8sw8F29pU277MJzBVc2nzsGuf2mQ3fZz2Reel3YOdv3r/U+cbaMMj+oPUOB/S0ymDbHjIsxYQmue4ya/mp+b1gB3qOS9AJDlWHDAjM1nH5TyIShmZmeYv3Q3CyCmkpMTw+2P50Zalu55ZnYZwGA9/qN/rEFB0mm+hq/q1nI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784908503; c=relaxed/simple; bh=+LlpLgT6kwy/yBhhVM/Uxqwvqr3VH/O/jaDZ77Jj0r8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AzrhJvKAzO9wjsomzuhE6ghdLgizUTkIdJNZ942vFBUp1X1nMSHj9j8F1KWPOdcCCkiVYSdtfvmSI46BPDdZJvk6r9rWdtR1czOW6tf/9/ROKbyht7fmfycddBMbwt3kZU2osgyyAn52FiwR/t5fNmOxUqxLGOARd4gnIYG17hw= 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=Y4F3qYic; arc=none smtp.client-ip=91.218.175.178 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="Y4F3qYic" Message-ID: <543929db-24c4-408c-99ae-99b4eca002e6@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784908499; 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=1LQaNR+lU++/LsUYSodNcVYtomEsMSpCfL3MqWelMpw=; b=Y4F3qYiciy9df5DUl5Ips0OECQOdiO4Ghd89lXJ/U1KXBheW+VpBQLsbcs+P+2frBJyT5q H2Cz2cXIyDDQDWWhbVryIY3gO81RTWD88V3eqsIqT/UrDOYxQW7sgkri6G0gFBKa8B6gPo CNpXwGoniCJbssQJ+8DmVQNkG42GqKw= Date: Fri, 24 Jul 2026 23:54:50 +0800 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next 1/2] bpf: Fix sleepable check for tracing prog To: Viktor Malik , bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan , Sechang Lim , Varun R Mallya , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org References: <20260724141422.10463-1-leon.hwang@linux.dev> <20260724141422.10463-2-leon.hwang@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Leon Hwang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2026/7/24 23:41, Viktor Malik wrote: > On 7/24/26 16:14, Leon Hwang wrote: >> When CONFIG_FUNCTION_ERROR_INJECTION is disabled, a sleepable tracing prog >> is allowed to attach to '__x64_'-alike prefix symbols. >> >> It is because the verifier does not verify whether the symbol is a kernel >> function or a bpf prog. That said, a sleepable tracing prog is allowed to >> attach to a bpf prog target whose name has '__x64_'-alike prefix. >> >> For example, a sleepable fentry prog attaches to a '__x64_sys_nop' XDP >> prog, and copies buffer from a user pointer with bpf_copy_from_user() >> helper. After attaching the XDP prog to lo interface, the kernel BUG >> could be triggered by 'ping -c 1 -W 1 127.0.0.1': >> >> [ 3.460756] BUG: sleeping function called from invalid context at kernel/bpf/trampoline.c:1324 >> >> Fix it by disallowing sleepable tracing prog always when its target is >> bpf prog. >> >> Fixes: 16d9c5660692 ("bpf: Always allow sleepable programs on syscalls") >> Signed-off-by: Leon Hwang >> --- >> kernel/bpf/verifier.c | 9 ++++++--- >> 1 file changed, 6 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >> index 52be0a118cce..40d567b90d24 100644 >> --- a/kernel/bpf/verifier.c >> +++ b/kernel/bpf/verifier.c >> @@ -18935,13 +18935,16 @@ static bool is_tracing_multi_id(const struct bpf_prog *prog, u32 btf_id) >> } >> >> static int btf_id_allow_sleepable(u32 btf_id, unsigned long addr, const struct bpf_prog *prog, >> - const struct btf *btf) >> + const struct btf *btf, const struct bpf_prog *tgt_prog) >> { >> const struct btf_type *t; >> const char *tname; >> >> switch (prog->type) { >> case BPF_PROG_TYPE_TRACING: >> + if (tgt_prog) >> + return prog->sleepable ? -EINVAL : 0; > > The prog->sleepable check is redundant since btf_id_allow_sleepable() is > only called if prog->sleepable is true. Good catch. Will drop the prog->sleepable check. > > Other than that: > > Acked-by: Viktor Malik Thanks for your review. Leon > [...]