From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Subject: Re: [PATCH] net: 6pack: fix slab-out-of-bounds in decode_data Date: Fri, 13 Aug 2021 17:58:34 +0300 Message-ID: <20210813145834.GC1931@kadam> References: <20210813112855.11170-1-paskripkin@gmail.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : content-type : in-reply-to : mime-version; s=corp-2021-07-09; bh=nIy5kOhV2tmCy63FhT/+hM0XM9wOm94PgL6RWcV/TAM=; b=eJ/YZw8Ad+v4CbUD8jyX1vTl/OT/tmyrHbLqNSI2RqsgXWNN+7XUDgUl1Gx9Ed6vEfx6 sAWHWKu5urBBy4QgYeRsE8IAXHDX7EQN/fT6+0WcQuqiayQLXZKYHd7baMF9hd9HaPII EIXWQb2VPIFSPj49kxkid2+xX44iPj1VWm427/NHTYl0KhH5JIZhQ01RaJX3WC/O/M/K Y3v6Vh7mZuDCICKu3ok2TcNa9vF0FNBZhX6gR62Y2t1Msif+PywRFEXqoNlVZ5utpFYA 4mR2dQduLY1DX+LsDMxRQ5a9iMtHQPvIPml4bMglKqte+oPrOB1mlLaaHo4S7YVswMQI 1A== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : content-type : in-reply-to : mime-version; s=corp-2020-01-29; bh=nIy5kOhV2tmCy63FhT/+hM0XM9wOm94PgL6RWcV/TAM=; b=bFKe5wHhkOOkbITLsUkL7YyMiWnBpxScOLhy7jy/mYisA7PuGcKdkVzJ9EMxMFjs9bzh rj6kZbEmWUZsVIqXqxCHOGO2KzAI199F5FtvNrR/ikDar5HRKru4B8tM+VpCwv/Mz4xq lp/GRaSFTZzkcXpl0H1/LvMGXHmecg+SEOzMresTIHp1NX4Doi/Co1xgyDsQP86CSqBl wwpYBlec5FnA5e+xLuMhC6FjMJVuzD1TlQmS5XVH+CWJ7j0X5kIDpyM6yNQ1Hyur0dxp epAlmTQ33+c1cpYpIjbF/9+JwTaoXlVCglknj96x3XPcYC35RB5JDCkm0mj4O7h4b+sl Pw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=nIy5kOhV2tmCy63FhT/+hM0XM9wOm94PgL6RWcV/TAM=; b=uov2IZwLyjUX2xo96tMeW3fXm8apfrlqa7Ua85ezEpZOw6js5xOA+S9AwSRIcvR7nOLsvDEk0d6CecHWAurvd6hWKaymWR/drNvmspkfuePPlWbQuVJrKVLA5cJ2vFXCQK1HjcSx7xBQZa7zNpw4qz4j9nXjFvMAv8MYXYwJHYg= Content-Disposition: inline In-Reply-To: <20210813112855.11170-1-paskripkin@gmail.com> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Pavel Skripkin Cc: ajk@comnets.uni-bremen.de, davem@davemloft.net, kuba@kernel.org, linux-hams@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+fc8cd9a673d4577fb2e4@syzkaller.appspotmail.com On Fri, Aug 13, 2021 at 02:28:55PM +0300, Pavel Skripkin wrote: > Syzbot reported slab-out-of bounds write in decode_data(). > The problem was in missing validation checks. > > Syzbot's reproducer generated malicious input, which caused > decode_data() to be called a lot in sixpack_decode(). Since > rx_count_cooked is only 400 bytes and noone reported before, > that 400 bytes is not enough, let's just check if input is malicious > and complain about buffer overrun. > > Fail log: > ================================================================== > BUG: KASAN: slab-out-of-bounds in drivers/net/hamradio/6pack.c:843 > Write of size 1 at addr ffff888087c5544e by task kworker/u4:0/7 > > CPU: 0 PID: 7 Comm: kworker/u4:0 Not tainted 5.6.0-rc3-syzkaller #0 > ... > Workqueue: events_unbound flush_to_ldisc > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x197/0x210 lib/dump_stack.c:118 > print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 > __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506 > kasan_report+0x12/0x20 mm/kasan/common.c:641 > __asan_report_store1_noabort+0x17/0x20 mm/kasan/generic_report.c:137 > decode_data.part.0+0x23b/0x270 drivers/net/hamradio/6pack.c:843 > decode_data drivers/net/hamradio/6pack.c:965 [inline] > sixpack_decode drivers/net/hamradio/6pack.c:968 [inline] > > Reported-and-tested-by: syzbot+fc8cd9a673d4577fb2e4@syzkaller.appspotmail.com > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Pavel Skripkin > --- > drivers/net/hamradio/6pack.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c > index fcf3af76b6d7..f4ffc2a80ab7 100644 > --- a/drivers/net/hamradio/6pack.c > +++ b/drivers/net/hamradio/6pack.c > @@ -827,6 +827,12 @@ static void decode_data(struct sixpack *sp, unsigned char inbyte) > return; > } > > + if (sp->rx_count_cooked + 3 >= sizeof(sp->cooked_buf)) { It should be + 2 instead of + 3. We write three bytes. idx, idx + 1, idx + 2. Otherwise, good fix! regards, dan carpenter