linux-kernel - Re: [PATCH v4] add the option of fortified string.h functions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1496439121.13303.1.camel@gmail.com>
Date:   Fri, 02 Jun 2017 17:32:01 -0400
From:   Daniel Micay <danielmicay@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, Kees Cook <keescook@...omium.org>,
        kernel-hardening@...ts.openwall.com,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Axtens <dja@...ens.net>,
        Moni Shoua <monis@...lanox.com>,
        Doug Ledford <dledford@...hat.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        linux-rdma@...r.kernel.org
Subject: Re: [PATCH v4] add the option of fortified string.h functions

On Fri, 2017-06-02 at 14:07 -0700, Andrew Morton wrote:
> On Fri, 26 May 2017 05:54:04 -0400 Daniel Micay <danielmicay@...il.com
> > wrote:
> 
> > This adds support for compiling with a rough equivalent to the glibc
> > _FORTIFY_SOURCE=1 feature, providing compile-time and runtime buffer
> > overflow checks for string.h functions when the compiler determines
> > the
> > size of the source or destination buffer at compile-time. Unlike
> > glibc,
> > it covers buffer reads in addition to writes.
> 
> Did we find a bug in drivers/infiniband/sw/rxe/rxe_resp.c?
> 
> i386 allmodconfig:
> 
> In file included from ./include/linux/bitmap.h:8:0,
>                  from ./include/linux/cpumask.h:11,
>                  from ./include/linux/mm_types_task.h:13,
>                  from ./include/linux/mm_types.h:4,
>                  from ./include/linux/kmemcheck.h:4,
>                  from ./include/linux/skbuff.h:18,
>                  from drivers/infiniband/sw/rxe/rxe_resp.c:34:
> In function 'memcpy',
>     inlined from 'send_atomic_ack.constprop' at
> drivers/infiniband/sw/rxe/rxe_resp.c:998:2,
>     inlined from 'acknowledge' at
> drivers/infiniband/sw/rxe/rxe_resp.c:1026:3,
>     inlined from 'rxe_responder' at
> drivers/infiniband/sw/rxe/rxe_resp.c:1286:10:
> ./include/linux/string.h:309:4: error: call to '__read_overflow2'
> declared with attribute error: detected read beyond size of object
> passed as 2nd parameter
>     __read_overflow2();
> 
> 
> If so, can you please interpret this for the infiniband developers?

It copies sizeof(skb->cb) bytes with memcpy which is 48 bytes since cb
is a 48 byte char array in `struct sk_buff`. The source buffer is a
`struct rxe_pkt_info`:

struct rxe_pkt_info {
	struct rxe_dev		*rxe;		/* device that owns packet */
	struct rxe_qp		*qp;		/* qp that owns packet */
	struct rxe_send_wqe	*wqe;		/* send wqe */
	u8			*hdr;		/* points to bth */
	u32			mask;		/* useful info about pkt */
	u32			psn;		/* bth psn of packet */
	u16			pkey_index;	/* partition of pkt */
	u16			paylen;		/* length of bth - icrc */
	u8			port_num;	/* port pkt received on */
	u8			opcode;		/* bth opcode of packet */
	u8			offset;		/* bth offset from pkt->hdr */
};

That looks like 32 bytes (1 byte of padding) on 32-bit and 48 bytes on
64-bit (1 byte of padding), so on 32-bit there's a read overflow of 16
bytes from the stack here.