openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 159 insertions, 0 deletions

diff --git a/scripts/extract-sys-certs.pl b/scripts/extract-sys-certs.pl
new file mode 100755
index 000000000..fa8ab1511
--- /dev/null
+++ b/scripts/extract-sys-certs.pl
@@ -0,0 +1,159 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+use warnings;
+use strict;
+use Math::BigInt;
+use Fcntl "SEEK_SET";
+
+die "Format: $0 [-s <systemmap-file>] <vmlinux-file> <keyring-file>\n"
+    if ($#ARGV != 1 && $#ARGV != 3 ||
+	$#ARGV == 3 && $ARGV[0] ne "-s");
+
+my $sysmap = "";
+if ($#ARGV == 3) {
+    shift;
+    $sysmap = $ARGV[0];
+    shift;
+}
+
+my $vmlinux = $ARGV[0];
+my $keyring = $ARGV[1];
+
+#
+# Parse the vmlinux section table
+#
+open FD, "objdump -h $vmlinux |" || die $vmlinux;
+my @lines = <FD>;
+close(FD) || die $vmlinux;
+
+my @sections = ();
+
+foreach my $line (@lines) {
+    chomp($line);
+    if ($line =~ /\s*([0-9]+)\s+(\S+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+2[*][*]([0-9]+)/
+	) {
+	my $seg  = $1;
+	my $name = $2;
+	my $len  = Math::BigInt->new("0x" . $3);
+	my $vma  = Math::BigInt->new("0x" . $4);
+	my $lma  = Math::BigInt->new("0x" . $5);
+	my $foff = Math::BigInt->new("0x" . $6);
+	my $align = 2 ** $7;
+
+	push @sections, { name => $name,
+			  vma => $vma,
+			  len => $len,
+			  foff => $foff };
+    }
+}
+
+print "Have $#sections sections\n";
+
+#
+# Try and parse the vmlinux symbol table.  If the vmlinux file has been created
+# from a vmlinuz file with extract-vmlinux then the symbol table will be empty.
+#
+open FD, "nm $vmlinux 2>/dev/null |" || die $vmlinux;
+@lines = <FD>;
+close(FD) || die $vmlinux;
+
+my %symbols = ();
+my $nr_symbols = 0;
+
+sub parse_symbols(@) {
+    foreach my $line (@_) {
+	chomp($line);
+	if ($line =~ /([0-9a-f]+)\s([a-zA-Z])\s(\S+)/
+	    ) {
+	    my $addr = "0x" . $1;
+	    my $type = $2;
+	    my $name = $3;
+
+	    $symbols{$name} = $addr;
+	    $nr_symbols++;
+	}
+    }
+}
+parse_symbols(@lines);
+
+if ($nr_symbols == 0 && $sysmap ne "") {
+    print "No symbols in vmlinux, trying $sysmap\n";
+
+    open FD, "<$sysmap" || die $sysmap;
+    @lines = <FD>;
+    close(FD) || die $sysmap;
+    parse_symbols(@lines);
+}
+
+die "No symbols available\n"
+    if ($nr_symbols == 0);
+
+print "Have $nr_symbols symbols\n";
+
+die "Can't find system certificate list"
+    unless (exists($symbols{"__cert_list_start"}) &&
+	    exists($symbols{"system_certificate_list_size"}));
+
+my $start = Math::BigInt->new($symbols{"__cert_list_start"});
+my $end;
+my $size;
+my $size_sym = Math::BigInt->new($symbols{"system_certificate_list_size"});
+
+open FD, "<$vmlinux" || die $vmlinux;
+binmode(FD);
+
+my $s = undef;
+foreach my $sec (@sections) {
+    my $s_name = $sec->{name};
+    my $s_vma = $sec->{vma};
+    my $s_len = $sec->{len};
+    my $s_foff = $sec->{foff};
+    my $s_vend = $s_vma + $s_len;
+
+    next unless ($start >= $s_vma);
+    next if ($start >= $s_vend);
+
+    die "Certificate list size was not found on the same section\n"
+	if ($size_sym < $s_vma || $size_sym > $s_vend);
+
+    die "Cert object in multiple sections: ", $s_name, " and ", $s->{name}, "\n"
+	if ($s);
+
+    my $size_off = $size_sym -$s_vma + $s_foff;
+    my $packed;
+    die $vmlinux if (!defined(sysseek(FD, $size_off, SEEK_SET)));
+    sysread(FD, $packed, 8);
+    $size = unpack 'L!', $packed;
+    $end = $start + $size;
+
+    printf "Have %u bytes of certs at VMA 0x%x\n", $size, $start;
+
+    die "Cert object partially overflows section $s_name\n"
+	if ($end > $s_vend);
+
+    $s = $sec;
+}
+
+die "Cert object not inside a section\n"
+    unless ($s);
+
+print "Certificate list in section ", $s->{name}, "\n";
+
+my $foff = $start - $s->{vma} + $s->{foff};
+
+printf "Certificate list at file offset 0x%x\n", $foff;
+
+die $vmlinux if (!defined(sysseek(FD, $foff, SEEK_SET)));
+my $buf = "";
+my $len = sysread(FD, $buf, $size);
+die "$vmlinux" if (!defined($len));
+die "Short read on $vmlinux\n" if ($len != $size);
+close(FD) || die $vmlinux;
+
+open FD, ">$keyring" || die $keyring;
+binmode(FD);
+$len = syswrite(FD, $buf, $size);
+die "$keyring" if (!defined($len));
+die "Short write on $keyring\n" if ($len != $size);
+close(FD) || die $keyring;