user-controllable kmalloc size in sctp_getsockopt_local_addrs

[Dmitry Vyukov]

Hello,

The following program triggers WARNING in kmalloc:

// autogenerated by syzkaller (http://github.com/google/syzkaller)
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/socket.h>
#include <linux/in.h>

#define SOL_SCTP 132
#define SCTP_GET_LOCAL_ADDRS 109

int main()
{
int fd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
char buf[256];
int len = 0x04000000;
getsockopt(fd, SOL_SCTP, SCTP_GET_LOCAL_ADDRS, &buf, &len);
return 0;
}



------------[ cut here ]------------
WARNING: CPU: 0 PID: 6006 at mm/page_alloc.c:2989
__alloc_pages_nodemask+0x695/0x14e0()
Modules linked in:
CPU: 0 PID: 6006 Comm: executor Not tainted 4.4.0-rc2+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
00000000ffffffff ffff880033887720 ffffffff82719fc6 0000000000000000
ffff8800338c2d80 ffffffff85a62a20 ffff880033887760 ffffffff81244ec9
ffffffff8154e3e5 ffffffff85a62a20 0000000000000bad 0000000000000000
Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff82719fc6>] dump_stack+0x68/0x92 lib/dump_stack.c:50
[<ffffffff81244ec9>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:460
[<ffffffff812450f9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:493
[< inline >] __alloc_pages_slowpath mm/page_alloc.c:2989
[<ffffffff8154e3e5>] __alloc_pages_nodemask+0x695/0x14e0 mm/page_alloc.c:3235
[<ffffffff8160ceee>] alloc_pages_current+0xee/0x340 mm/mempolicy.c:2055
[< inline >] alloc_pages include/linux/gfp.h:451
[<ffffffff81549c56>] alloc_kmem_pages+0x16/0xf0 mm/page_alloc.c:3414
[<ffffffff81595e79>] kmalloc_order+0x19/0x60 mm/slab_common.c:1007
[<ffffffff81595edf>] kmalloc_order_trace+0x1f/0xa0 mm/slab_common.c:1018
[< inline >] kmalloc_large include/linux/slab.h:390
[<ffffffff8161bd74>] __kmalloc+0x234/0x250 mm/slub.c:3525
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] sctp_getsockopt_local_addrs net/sctp/socket.c:4931
[<ffffffff854d9730>] sctp_getsockopt+0x11b0/0x3e00 net/sctp/socket.c:6007
[<ffffffff84913ad5>] sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2604
[< inline >] SYSC_getsockopt net/socket.c:1788
[<ffffffff84911282>] SyS_getsockopt+0x142/0x230 net/socket.c:1770
[<ffffffff859551f6>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
---[ end trace 42716df2ed49f73e ]---


On commit 78c4a49a69e910a162b05e4e8727b9bdbf948f13 (Nov 25).

[Marcelo Ricardo Leitner]

On Sat, Nov 28, 2015 at 01:40:08PM +0100, Dmitry Vyukov wrote:
> Hello,
>
> The following program triggers WARNING in kmalloc:
>

I messed up with the in-reply-to, put an extra c on it, but I just
posted a patch for this, subject:
[PATCH] sctp: use GFP_USER for user-controlled kmalloc

Thanks,
Marcelo