From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 281DD415F02; Tue, 21 Jul 2026 18:15:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784657737; cv=none; b=BvzlE0LhrL91Jid1ZoMbXXn04Up/uCIiMzuXeI+BwfPgkaW4HsIJlDviX37ilFTSb6a7EdygAVRUzH/epjXKJ6juvfl6C7NgigeQ4G+hjIhOs2RgN51T2PJjgt/BOas/oL0jVTjDiCJv2X/e9qBSlqqGYn6BquYW6E7XEvpIzxc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784657737; c=relaxed/simple; bh=8bD9KW1ZiCYdSnVTIpf1KZFD2uDJLrK8IFGV4+ycLcA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=B+IW/MokaW46PfQO2x7FPT4xeFwea8AhYm/jnccYHKyQqMpnSkHR9/UzzghBjXmsqvpVdUnYJyKqV8LvwVe1uKHxdwtHEdxXO+KJhoz+e1DkveJ8y7YYWLSloxSunFdqs1RbZiJP3xF4HLdLwC/PxyGbxrZ14880fIB6M/CVThY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bzkI3si1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bzkI3si1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 952EC1F000E9; Tue, 21 Jul 2026 18:15:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784657736; bh=meNX2lrHsU/8iYtr/CIpFYqv5z8uhnpsYVdNNb5f7C4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bzkI3si1e0ghsEStxKITwLqWbVg8nz48JZF37yhi7OHpZF2uKezUZ4GQscAGjdrvb 4VEDthK8+JzgNBjv4tskV7l55qY7iD70jlbp2eX0B7j3ANon25zp+HQkD7jzNlI2F+ E3yW/oSx/cbF9go8d51oVCJPzAF4TJXy+qCNHQuQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Luis Gerhorst , Jiayuan Chen , Emil Tsalapatis , Nuoqi Gui , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.18 0876/1611] bpf: Fix stack slot index in nospec checks Date: Tue, 21 Jul 2026 17:16:32 +0200 Message-ID: <20260721152535.094562848@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nuoqi Gui [ Upstream commit d1d53aa30ab3b5ae89161c9cc840b3f7489ad386 ] 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: 2039f26f3aca ("bpf: Fix leakage due to insufficient speculative store bypass mitigation") Acked-by: Luis Gerhorst Reviewed-by: Jiayuan Chen Reviewed-by: Emil Tsalapatis Signed-off-by: Nuoqi Gui Link: https://lore.kernel.org/r/20260618-f01-11-stack-nospec-slot-index-v3-1-780297041721@mails.tsinghua.edu.cn Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index bf8cadd19593b2..99fa175e8ef89c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5143,7 +5143,8 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env, bool sanitize = reg && is_spillable_regtype(reg->type); for (i = 0; i < size; i++) { - u8 type = state->stack[spi].slot_type[i]; + u8 type = state->stack[spi].slot_type[(slot - i) % + BPF_REG_SIZE]; if (type != STACK_MISC && type != STACK_ZERO) { sanitize = true; -- 2.53.0