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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id g98si43212pje.92.2019.08.07.12.58.29 for (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 07 Aug 2019 12:58:29 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=NKiybbKg; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=0khcKVDc1M1qvkv6DyyrH2FLY7iQ9qgNyVVoVFfpCEY=; b=NKiybbKgcU+q44Ei2Q7De+6iG ztSVcmsSn3guhAcPw69spDGchYJkKSr1zXigAqS6E+/ezF9+17Tb+bACFAXyPfUqF/uFE0MY485Tg fB+PtHAnG4/yAHlBfyE/FFeAvsWT+B00FogAwQYkPKzKvRauSfgXOcvkb9Koh/u9Gb4PI1GoAEOES 3Anly3YV9QI6OjClj93Ke5Yz6q8JbpuvvuNMDrJ6Z2XOrTA3dWNiKylx+0PaB+GYdZpDq5oPLm6iz QyUpcCEL7SDOvTvaiyoK7SPkfuTN/IJHhdVmQY2GbhB0lXBj28pRQ9M1sw38VJgN+0meBi77p0wAu t0Ume/Jnw==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hvS4j-0008Gx-Ai; Wed, 07 Aug 2019 19:58:21 +0000 Date: Wed, 7 Aug 2019 12:58:21 -0700 From: Matthew Wilcox To: syzbot Cc: allison@lohutok.net, andreyknvl@google.com, cai@lca.pw, gregkh@linuxfoundation.org, keescook@chromium.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, Jiri Kosina Subject: Re: BUG: bad usercopy in hidraw_ioctl Message-ID: <20190807195821.GD5482@bombadil.infradead.org> References: <000000000000ce6527058f8bf0d0@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <000000000000ce6527058f8bf0d0@google.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Aug 07, 2019 at 12:28:06PM -0700, syzbot wrote: > usercopy: Kernel memory exposure attempt detected from wrapped address > (offset 0, size 0)! > ------------[ cut here ]------------ > kernel BUG at mm/usercopy.c:98! This report is confusing because the arguments to usercopy_abort() are wrong. /* Reject if object wraps past end of memory. */ if (ptr + n < ptr) usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n); ptr + n is not 'size', it's what wrapped. I don't know what 'offset' should be set to, but 'size' should be 'n'. Presumably we don't want to report 'ptr' because it'll leak a kernel address ... reporting 'n' will leak a range for a kernel address, but I think that's OK? Admittedly an attacker can pass in various values for 'n', but it'll be quite noisy and leave a trace in the kernel logs for forensics to find afterwards. > Call Trace: > check_bogus_address mm/usercopy.c:151 [inline] > __check_object_size mm/usercopy.c:260 [inline] > __check_object_size.cold+0xb2/0xba mm/usercopy.c:250 > check_object_size include/linux/thread_info.h:119 [inline] > check_copy_size include/linux/thread_info.h:150 [inline] > copy_to_user include/linux/uaccess.h:151 [inline] > hidraw_ioctl+0x38c/0xae0 drivers/hid/hidraw.c:392 The root problem would appear to be: else if (copy_to_user(user_arg + offsetof( struct hidraw_report_descriptor, value[0]), dev->hid->rdesc, min(dev->hid->rsize, len))) That 'min' should surely be a 'max'? Jiri, this looks like it was your code back in 2007.