From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yx1-f46.google.com (mail-yx1-f46.google.com [74.125.224.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59878280A5A for ; Sat, 6 Dec 2025 14:12:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.224.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765030359; cv=none; b=AQedsZCwAv1jPAw3/NLMbnEaY1jrSS7B3CRbyns+o1Ea2+B0wSKjhFk+QBdMcSeDp8iHVh4lkDw0BLXSnz3g3SJnO8FyITXUFB6KQgsWP26BasLWK1m4lyBb6QzXyRKSGhj77HAyWSHnLpYo/8CxH0jm/DrEqU9n9LQvmk3c+BU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765030359; c=relaxed/simple; bh=S+igu4aju7EwXWFRbjCCQgO7Bx4KXZSG7GeZGRqJ1fM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OKml10v1FPa/py21wFMYPkeiaPglDhtwPz3S2uROxLH18SeO9FKeQF3iQNvn3yn9pnfYm/DO2xA8TtieeRxtbM6mud0UaPbVrzXL7+lmI3hF1ZW7fnkHSGizXclMwGtFt/6MVsu/hQYJfqmnYeYcZQRQpo5hSpPYsyoFHYUI8CQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=GmHhnHMJ; arc=none smtp.client-ip=74.125.224.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GmHhnHMJ" Received: by mail-yx1-f46.google.com with SMTP id 956f58d0204a3-640f2c9cc72so2826210d50.3 for ; Sat, 06 Dec 2025 06:12:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1765030357; x=1765635157; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=fX6x8dKVuvuScvQG43b+CJnQqhUVfctvBR8HYubZTkk=; b=GmHhnHMJtWXo5n9JfVX7awchSCfxN0g9ni8gmCegbPDs/e53eS0IOAmVGEuZot+rSa JV2GtmuVczlxmjS8CQCGvkN0JjMqGlIpo0RNGgQXztIsMZYYCkRFcqJDlnWSmfl5URtc zloliAFuImbfZqC2o07VWMhrYcucQrnnQ8+Tdoe0Ng7KkNrxEai8pByu5PLmaJr1vkTl v96uNKBpGlt7n7yflVkrYvwdHn6ruQMDVDjoM1wqwFb71AR9JA4LgljVUePly0p8x5vd 0kfBxp0ivJijzhOwD7GqNSrQpf9h9qlnapG0OLtpWe4NAde6qhE15/z0NR0jHeA9+E+b 6xbQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1765030357; x=1765635157; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=fX6x8dKVuvuScvQG43b+CJnQqhUVfctvBR8HYubZTkk=; b=fCmrIsfzRAqfG1/iGSdx5553wUBaG1RykVizlBDOsdcbZzoP3ldnuyi6kNmBAzyWER MIYANk1UJpTDgpXwhxpijgXo49dDFxsj6MOPrIoVMKXh7FXXv8F4bKcMvddEg/+gTcHQ 3Bd0AmMSidMiNyVkRSQfC3m64rlnqVU2Fx5bdRuWcp26Gebrf1qUp7iRj+68AH6TfEMX iRUPBe2dkGDHhCd/6sQ2bbWv8xAeO6vDJuYALqdYVOwZpKuKCF/aowIlPTdheydjkrw7 cA3rLyQ+8r4Ixn8bAiDrmtGrii/g34iCoF0drsUm1jafv1rbRPK9I0SxiwYnkFpKQ0IL o1ZQ== X-Forwarded-Encrypted: i=1; AJvYcCUtz/QG6YIAMBf5Unf8qBvKnR+R7MinTyLTAgbf5shFlg2/8B7RcQOaAQcJeKYUe1F4pqA=@vger.kernel.org X-Gm-Message-State: AOJu0Yz86repRoUEGBz4/kh5jHcuVxWYVU7ySyXzRrT0XEVWYH3q/pVu rOpNt1g+b3o3JtvB6LXF6+KdcnPqJYmx/K14NmfWwtMEf0CIj8T4NdLe X-Gm-Gg: ASbGncsjTiJWaOusezxVyjbNWheThYoMnXD9QCJgwdrO2QhoZXGTW08uoAPXda9oZZ3 3BJu2LbkaOnQH4vHROnp7rNfxdQrTvtwD3oPEpEvgJkhuGsf8tvvYUg3OSvGSoKix8s3kNleUwC SRTVz93IFBWs48G/6IooJIhRVkbXTO+QWSIDgI9nXNLenWSL+YVoxVdiu9JqeqZ0uL7Q94Fcn9+ ZU3guzO8G7078nxNKmj94psOQS/brTGUdw+hwMb1A072LD/laQthcCnxElIJi3BKUBxcK+Kh95X 9kQHb+Fs2gtNLZvXNXPulCgShFtXaQZCJH/FuLAEIcRfOXno4iA1N637A40a3K0ny8mmZxEfs9L iWLNAHWwm2He33CtjZajaJq57QT8FuUkJTADdq5M/HL3IjkKhEJrFlpUrKY+N9T6HIrlvtqgtB+ BOhJPgMpH+lPDkReQhzymy363Yt+Vx+HJFbjPrw0B1AdbWVSwXFmr7HUzj+DNKnA== X-Google-Smtp-Source: AGHT+IHuF83mFXlkaMu6oHm6oMBi8mfMFdfNONlXiyds7RYNVDtirN1s6Te2e+85GpStdEubYV2j5g== X-Received: by 2002:a05:690c:64c2:b0:788:181b:869e with SMTP id 00721157ae682-78c33c171bemr42202787b3.40.1765030357161; Sat, 06 Dec 2025 06:12:37 -0800 (PST) Received: from localhost.localdomain (45.62.117.175.16clouds.com. [45.62.117.175]) by smtp.gmail.com with ESMTPSA id 00721157ae682-78c1b4ae534sm28038027b3.3.2025.12.06.06.12.31 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 06 Dec 2025 06:12:36 -0800 (PST) From: Shuran Liu To: song@kernel.org, mattbobrowski@google.com, bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, dxu@dxuuu.xyz, linux-kselftest@vger.kernel.org, shuah@kernel.org, electronlsr@gmail.com, Zesen Liu , Peili Gao , Haoran Ni Subject: [PATCH bpf v5 1/2] bpf: mark bpf_d_path() buffer as writeable Date: Sat, 6 Dec 2025 22:12:09 +0800 Message-ID: <20251206141210.3148-2-electronlsr@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251206141210.3148-1-electronlsr@gmail.com> References: <20251206141210.3148-1-electronlsr@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Commit 37cce22dbd51 ("bpf: verifier: Refactor helper access type tracking") started distinguishing read vs write accesses performed by helpers. The second argument of bpf_d_path() is a pointer to a buffer that the helper fills with the resulting path. However, its prototype currently uses ARG_PTR_TO_MEM without MEM_WRITE. Before 37cce22dbd51, helper accesses were conservatively treated as potential writes, so this mismatch did not cause issues. Since that commit, the verifier may incorrectly assume that the buffer contents are unchanged across the helper call and base its optimizations on this wrong assumption. This can lead to misbehaviour in BPF programs that read back the buffer, such as prefix comparisons on the returned path. Fix this by marking the second argument of bpf_d_path() as ARG_PTR_TO_MEM | MEM_WRITE so that the verifier correctly models the write to the caller-provided buffer. Fixes: 37cce22dbd51 ("bpf: verifier: Refactor helper access type tracking") Co-developed-by: Zesen Liu Signed-off-by: Zesen Liu Co-developed-by: Peili Gao Signed-off-by: Peili Gao Co-developed-by: Haoran Ni Signed-off-by: Haoran Ni Signed-off-by: Shuran Liu Reviewed-by: Matt Bobrowski --- kernel/trace/bpf_trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 4f87c16d915a..49e0bdaa7a1b 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -965,7 +965,7 @@ static const struct bpf_func_proto bpf_d_path_proto = { .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_BTF_ID, .arg1_btf_id = &bpf_d_path_btf_ids[0], - .arg2_type = ARG_PTR_TO_MEM, + .arg2_type = ARG_PTR_TO_MEM | MEM_WRITE, .arg3_type = ARG_CONST_SIZE_OR_ZERO, .allowed = bpf_d_path_allowed, }; -- 2.52.0