From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f46.google.com (mail-wm1-f46.google.com [209.85.128.46]) (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 8629A262B6; Sun, 2 Jun 2024 19:32:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717356759; cv=none; b=scEQLS/1nN+oEh+rBrzUM+JvEx0zijkfeZTDCLSu2WySxVvSn7wBntHB+d2fLfSYMtWyXPlY5fDEKKFzO+5rQsNXn4LUOW1X095DZ9ZGiugereSCvQDU+5j7mu3hKnqNM6qG7+Yoh1JcGU9yYNRtO3QaAX/o3Cd/GP3uUlomEgk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717356759; c=relaxed/simple; bh=jIno1JF/zaBu1ybGTRfJ2FsZUbHpL9bl8tN6FO+8hLI=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GoYPvCfvEmGutKJGCEcv5ImIX7CdNNsCVS1u21crjmEtpHp+E7uPRSDqzenPKJPWQWtwJNcYv0fYPzC/yXc9zen3oGo8SqIEG7DLd8/Akk4epw6nTNA+6V/f21BH4Lxx29J+k0w3hB9GZR+ttOX/qCSosXoxm+ZMOLbXpe8CW3I= 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=GbI4sD15; arc=none smtp.client-ip=209.85.128.46 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="GbI4sD15" Received: by mail-wm1-f46.google.com with SMTP id 5b1f17b1804b1-421338c4c3bso15185125e9.1; Sun, 02 Jun 2024 12:32:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1717356756; x=1717961556; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=lKCOsV2XYSwYAbin9usnjEvg6RDHEVLVcrQaFWDC7m0=; b=GbI4sD15ZU0Je0FaUTfxG4q9X1Sn/UXD/6ViACsnvAGzxj4DAPeS2Uj4+6FUrstT1V YMg3TIrN2jMvPe8B5KSwkfKgI59Tj3Dw7/h16+zdMczzwgReU0D6BTlV6KS4nm+wBmlV Os6nwUuBzxwcRX77V/Bo7IGdOUlLcQHZuG0KDyjkB2YoBWa5UzVZRK+ZnU+3jz4nKeMv 6Qu+QPcM0G3ms/6Q6Qay7hWduOARJMZ70JyOQtjfl0FIkYBCuQe1v3sZO/kK8b+9Vl9z e5JtzAiXT2HdsztaRlxkqnHpUE3/rdHbVI9Wy8agA1PihZQWmKM0/jV/cDDze09+pZXO 9hUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1717356756; x=1717961556; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=lKCOsV2XYSwYAbin9usnjEvg6RDHEVLVcrQaFWDC7m0=; b=r8gMDG/9IrfuojA9t30pUYo1SHOPFGfchhKuju7/n2fPRlOqJ4IT0hezEpf/pVNBZw ud+rWOM3OtMaYl3ziGNvW9yMXrAC70fHDz/kYKHU5j4l0ImUpER7am2NdwKuFpKzqrj2 DlmWmmJer40FboCPEd73ik3bMcHRncE8MA9aFd/EHp0StLE5eylOfiU78Z96I2Ugv1Bg zct7SFhJ8XAF6Su9/Oemimn2IT98NqtXgJ+1poymZS9Eg2aLQfoj0ARGhdEhvGbhaqKV 3SMfYc1YUClkZgRIc+U/wyQwLthyMUTb+mxU3TQo/6x0MXEU860Y7p4vVYogG1mTkc0A bvww== X-Forwarded-Encrypted: i=1; AJvYcCXIMSfSPJHel9qqpwfcJhRpnIw0u9p+ESN4GUZDvRoFcS74x0oX9gwgroYaTo8H6mtwiCuzRAKQRHuumFUcuJ6EqA9z X-Gm-Message-State: AOJu0Yw3QXxgkM+8tvI3c1QpFpi93kABPCzxj+q9agGmWmaY2x9cCV3n 69q0R5D4/u18OUYgljtDGFQBlddfyAYopkOfVvAhcq48yIq61ZVK X-Google-Smtp-Source: AGHT+IE0wIV1lHMQma4StsOqMl/QcsD2jWifORtX8XnqJREO7HxFU7LfOfxBZ7lixUh2Jjyb/RaZBA== X-Received: by 2002:a05:600c:6ca:b0:41a:b961:9495 with SMTP id 5b1f17b1804b1-4212e09cc32mr57986895e9.25.1717356755591; Sun, 02 Jun 2024 12:32:35 -0700 (PDT) Received: from krava ([83.240.60.202]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4213411b25dsm68313655e9.40.2024.06.02.12.32.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 02 Jun 2024 12:32:35 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Sun, 2 Jun 2024 21:32:33 +0200 To: Cong Wang Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Cong Wang , syzbot+1989ee16d94720836244@syzkaller.appspotmail.com, Andrii Nakryiko Subject: Re: [Patch bpf] bpf: fix a potential use-after-free in bpf_link_free() Message-ID: References: <20240602182703.207276-1-xiyou.wangcong@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240602182703.207276-1-xiyou.wangcong@gmail.com> On Sun, Jun 02, 2024 at 11:27:03AM -0700, Cong Wang wrote: > From: Cong Wang > > After commit 1a80dbcb2dba, bpf_link can be freed by > link->ops->dealloc_deferred, but the code still tests and uses > link->ops->dealloc afterward, which leads to a use-after-free as > reported by syzbot. Actually, one of them should be sufficient, so > just call one of them instead of both. Also add a WARN_ON() in case > of any problematic implementation. > > Reported-by: syzbot+1989ee16d94720836244@syzkaller.appspotmail.com > Fixes: 1a80dbcb2dba ("bpf: support deferring bpf_link dealloc to after RCU grace period") > Cc: Andrii Nakryiko > Signed-off-by: Cong Wang > --- > kernel/bpf/syscall.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 2222c3ff88e7..d8f244069495 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -2998,6 +2998,7 @@ static int bpf_obj_get(const union bpf_attr *attr) > void bpf_link_init(struct bpf_link *link, enum bpf_link_type type, > const struct bpf_link_ops *ops, struct bpf_prog *prog) > { > + WARN_ON(ops->dealloc && ops->dealloc_deferred); > atomic64_set(&link->refcnt, 1); > link->type = type; > link->id = 0; > @@ -3074,8 +3075,7 @@ static void bpf_link_free(struct bpf_link *link) > call_rcu_tasks_trace(&link->rcu, bpf_link_defer_dealloc_mult_rcu_gp); > else > call_rcu(&link->rcu, bpf_link_defer_dealloc_rcu_gp); > - } > - if (link->ops->dealloc) > + } else if (link->ops->dealloc) > link->ops->dealloc(link); nice catch Acked-by: Jiri Olsa jirka