x32: Use compat shims for {g,s}etsockopt

Some of the arguments to {g,s}etsockopt are passed in userland pointers.
If we try to use the 64bit entry point, we end up sometimes failing.

For example, dhcpcd doesn't run in x32:
	# dhcpcd eth0
	dhcpcd[1979]: version 5.5.6 starting
	dhcpcd[1979]: eth0: broadcasting for a lease
	dhcpcd[1979]: eth0: open_socket: Invalid argument
	dhcpcd[1979]: eth0: send_raw_packet: Bad file descriptor

The code in particular is getting back EINVAL when doing:
	struct sock_fprog pf;
	setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &pf, sizeof(pf));

Diving into the kernel code, we can see:
include/linux/filter.h:
	struct sock_fprog {
		unsigned short len;
		struct sock_filter __user *filter;
	};

net/core/sock.c:
	case SO_ATTACH_FILTER:
		ret = -EINVAL;
		if (optlen == sizeof(struct sock_fprog)) {
			struct sock_fprog fprog;

			ret = -EFAULT;
			if (copy_from_user(&fprog, optval, sizeof(fprog)))
				break;

			ret = sk_attach_filter(&fprog, sk);
		}
		break;

arch/x86/syscalls/syscall_64.tbl:
	54 common setsockopt sys_setsockopt
	55 common getsockopt sys_getsockopt

So for x64, sizeof(sock_fprog) is 16 bytes.  For x86/x32, it's 8 bytes.
This comes down to the pointer being 32bit for x32, which means we need
to do structure size translation.  But since x32 comes in directly to
sys_setsockopt, it doesn't get translated like x86.

After changing the syscall table and rebuilding glibc with the new kernel
headers, dhcp runs fine in an x32 userland.

Oddly, it seems like Linus noted the same thing during the initial port,
but I guess that was missed/lost along the way:
	https://lkml.org/lkml/2011/8/26/452

[ hpa: tagging for -stable since this is an ABI fix. ]

Bugzilla: https://bugs.gentoo.org/423649
Reported-by: Mads <mads@ab3.no>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Link: http://lkml.kernel.org/r/1345320697-15713-1-git-send-email-vapier@gentoo.org
Cc: H. J. Lu <hjl.tools@gmail.com>
Cc: <stable@vger.kernel.org> v3.4..v3.5
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index 29aed7ac2c02..a582bfed95bb 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -60,8 +60,8 @@
 51      common  getsockname             sys_getsockname
 52      common  getpeername             sys_getpeername
 53      common  socketpair              sys_socketpair
-54      common  setsockopt              sys_setsockopt
-55      common  getsockopt              sys_getsockopt
+54      64      setsockopt              sys_setsockopt
+55      64      getsockopt              sys_getsockopt
 56      common  clone                   stub_clone
 57      common  fork                    stub_fork
 58      common  vfork                   stub_vfork
@@ -353,3 +353,5 @@
 538     x32     sendmmsg                compat_sys_sendmmsg
 539     x32     process_vm_readv        compat_sys_process_vm_readv
 540     x32     process_vm_writev       compat_sys_process_vm_writev
+541     x32     setsockopt              compat_sys_setsockopt
+542     x32     getsockopt              compat_sys_getsockopt