From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) (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 697B93793B5 for ; Wed, 17 Jun 2026 11:09:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781694549; cv=none; b=lLs8mSBTOnd5MEiq3Vqq1dpTpTXnD3/pcitlrgR5P9UxSaQGU9PJv+PaRYCXFIlrWa+femp0wUHzLRL3CP7c3IaLp0Dyk/xPm7STDpnwpJleg5Y9dX7uZYxxFuW9KQIsg63Y0mgZ1qhJgNB9YTTJAu9hb3//M1kmyOjqkltGrGk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781694549; c=relaxed/simple; bh=XzP0Cyg7IV+GZuzJzF01SzhIskMBRbALCcY9nKUynKI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=V75YFnIibTGB+C6NM7XRXqlMJZksGGg/ApYLM0muG6aJOLPB+hsHh066lg6aEgiDL69b/r4xwHDGlP8+/JImuhSGJPfHacl7lT7oZhMv4OdKggEmZgghKcubKzk1888L4q4GOua87cW5K25dT8xaaXojzZ3giJLEVPufheYyC8E= 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=HJvYPWTP; arc=none smtp.client-ip=95.215.58.170 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="HJvYPWTP" Message-ID: <14d43777-e979-42b4-a9ec-cc5d46f4e01e@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781694544; 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=hit5OWWdmyaqHN3p4Sv7rLdforBDEson2Ovw95DWC3o=; b=HJvYPWTPl7x7tkSX4cfnotjTzOBWQd9dE5AfyePTqFzwNeijn7f70P0KFkpnlILfgL1h7z tGGAm8eqzsxC/ndCNRdvXEsbJWpeq/4ndE35vBrPyIJJdJnWld0l/9T7ez7JgQqwEM4xcj PuAJ8MNaEblHLune/5T2sOpib1FndjE= Date: Wed, 17 Jun 2026 19:08:40 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf 1/2] bpf: Fix stack slot index in nospec checks To: Nuoqi Gui , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Emil Tsalapatis Cc: John Fastabend , Martin KaFai Lau , Luis Gerhorst , Shuah Khan , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260617-f01-11-stack-nospec-slot-index-v1-0-e3a080b0cd7e@mails.tsinghua.edu.cn> <20260617-f01-11-stack-nospec-slot-index-v1-1-e3a080b0cd7e@mails.tsinghua.edu.cn> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Jiayuan Chen In-Reply-To: <20260617-f01-11-stack-nospec-slot-index-v1-1-e3a080b0cd7e@mails.tsinghua.edu.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 6/17/26 12:57 AM, Nuoqi Gui wrote: > check_stack_write_fixed_off() computes the byte slot for a fixed-offset > stack write as -off - 1, and records each written byte in slot_type[] with > (slot - i) % BPF_REG_SIZE. > > The Spectre v4 sanitization pre-check uses slot_type[i] instead. For a > 4-byte write at fp-8 after the lower half of fp-8 has been zeroed, the > pre-check scans bytes 0..3 and sees STACK_ZERO while the actual write updates > bytes 7..4. That can leave the second half-slot write without nospec_result > even though the bytes being overwritten still require sanitization. > > Use the same slot index in the sanitization pre-check that the write path uses > when updating slot_type[]. > > Fixes: e4f4db47794c ("bpf: Fix pointer-leak due to insufficient speculative store bypass mitigation") > Signed-off-by: Nuoqi Gui I think the Fixes tag should be  2039f26f3aca ("bpf: Fix leakage due to insufficient speculative store bypass mitigation") ? Otherwise, looks good to me. Reviewed-by: Jiayuan Chen