From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Date: Fri, 07 Aug 2020 18:29:19 +0000 Subject: Re: [PATCH 25/26] net: pass a sockptr_t into ->setsockopt Message-Id: <90f626a4-d9e5-91a5-b71d-498e3b125da1@gmail.com> List-Id: References: <20200723060908.50081-1-hch@lst.de> <20200723060908.50081-26-hch@lst.de> <6357942b-0b6e-1901-7dce-e308c9fac347@gmail.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Laight , 'Eric Dumazet' , Christoph Hellwig , "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Alexey Kuznetsov , Hideaki YOSHIFUJI , Eric Dumazet Cc: "linux-crypto@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "bpf@vger.kernel.org" , "netfilter-devel@vger.kernel.org" , "coreteam@netfilter.org" , "linux-sctp@vger.kernel.org" , "linux-hams@vger.kernel.org" , "linux-bluetooth@vger.kernel.org" , "bridge@lists.linux-foundation.org" , "linux-can@vger.kernel.org" , "dccp@vger.kernel.org" , "linux-decnet-user@lists.sourceforge.net" , "linux-wpan@vger.kernel.org" , "linux-s390@vger.kernel.org" , "mptcp@lists.01.org" , "lvs-devel@vger.kernel.org" , "rds-devel@oss.oracle.com" , "linux-afs@lists.infradead.org" , "tipc-discussion@lists.sourceforge.net" , "linux-x25@vger.kernel.org" , Stefan Schmidt On 8/7/20 2:18 AM, David Laight wrote: > From: Eric Dumazet >> Sent: 06 August 2020 23:21 >> >> On 7/22/20 11:09 PM, Christoph Hellwig wrote: >>> Rework the remaining setsockopt code to pass a sockptr_t instead of a >>> plain user pointer. This removes the last remaining set_fs(KERNEL_DS) >>> outside of architecture specific code. >>> >>> Signed-off-by: Christoph Hellwig >>> Acked-by: Stefan Schmidt [ieee802154] >>> --- >> >> >> ... >> >>> diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c >>> index 594e01ad670aa6..874f01cd7aec42 100644 >>> --- a/net/ipv6/raw.c >>> +++ b/net/ipv6/raw.c >>> @@ -972,13 +972,13 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) >>> } >>> >> >> ... >> >>> static int do_rawv6_setsockopt(struct sock *sk, int level, int optname, >>> - char __user *optval, unsigned int optlen) >>> + sockptr_t optval, unsigned int optlen) >>> { >>> struct raw6_sock *rp = raw6_sk(sk); >>> int val; >>> >>> - if (get_user(val, (int __user *)optval)) >>> + if (copy_from_sockptr(&val, optval, sizeof(val))) >>> return -EFAULT; >>> >> >> converting get_user(...) to copy_from_sockptr(...) really assumed the optlen >> has been validated to be >= sizeof(int) earlier. >> >> Which is not always the case, for example here. >> >> User application can fool us passing optlen=0, and a user pointer of exactly TASK_SIZE-1 > > Won't the user pointer force copy_from_sockptr() to call > copy_from_user() which will then do access_ok() on the entire > range and so return -EFAULT. > > The only problems arise if the kernel code adds an offset to the > user address. > And the later patch added an offset to the copy functions. I dunno, I definitely got the following syzbot crash No repro found by syzbot yet, but I suspect a 32bit binary program did : setsockopt(fd, 0x29, 0x24, 0xffffffffffffffff, 0x0) BUG: KASAN: wild-memory-access in memcpy include/linux/string.h:406 [inline] BUG: KASAN: wild-memory-access in copy_from_sockptr_offset include/linux/sockptr.h:71 [inline] BUG: KASAN: wild-memory-access in copy_from_sockptr include/linux/sockptr.h:77 [inline] BUG: KASAN: wild-memory-access in do_rawv6_setsockopt net/ipv6/raw.c:1023 [inline] BUG: KASAN: wild-memory-access in rawv6_setsockopt+0x1a1/0x6f0 net/ipv6/raw.c:1084 Read of size 4 at addr 00000000ffffffff by task syz-executor.0/28251 CPU: 3 PID: 28251 Comm: syz-executor.0 Not tainted 5.8.0-syzkaller #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x18f/0x20d lib/dump_stack.c:118 __kasan_report mm/kasan/report.c:517 [inline] kasan_report.cold+0x5/0x37 mm/kasan/report.c:530 check_memory_region_inline mm/kasan/generic.c:186 [inline] check_memory_region+0x13d/0x180 mm/kasan/generic.c:192 memcpy+0x20/0x60 mm/kasan/common.c:105 memcpy include/linux/string.h:406 [inline] copy_from_sockptr_offset include/linux/sockptr.h:71 [inline] copy_from_sockptr include/linux/sockptr.h:77 [inline] do_rawv6_setsockopt net/ipv6/raw.c:1023 [inline] rawv6_setsockopt+0x1a1/0x6f0 net/ipv6/raw.c:1084 __sys_setsockopt+0x2ad/0x6d0 net/socket.c:2138 __do_sys_setsockopt net/socket.c:2149 [inline] __se_sys_setsockopt net/socket.c:2146 [inline] __ia32_sys_setsockopt+0xb9/0x150 net/socket.c:2146 do_syscall_32_irqs_on arch/x86/entry/common.c:84 [inline] __do_fast_syscall_32+0x57/0x80 arch/x86/entry/common.c:126 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:149 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c RIP: 0023:0xf7f22569 Code: c4 01 10 03 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 RSP: 002b:00000000f551c0bc EFLAGS: 00000296 ORIG_RAX: 000000000000016e RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000029 RDX: 0000000000000024 RSI: 00000000ffffffff RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 =================================