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, 132 insertions, 0 deletions

diff --git a/scripts/kconfig/kconfig-sym-check.pl b/scripts/kconfig/kconfig-sym-check.pl
new file mode 100755
index 000000000..daa5285fd
--- /dev/null
+++ b/scripts/kconfig/kconfig-sym-check.pl
@@ -0,0 +1,132 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+
+use warnings;
+use strict;
+
+my $srctree = shift @ARGV;
+unless (defined $srctree) {
+	$srctree = `git rev-parse --show-toplevel 2>/dev/null`;
+	chomp $srctree;
+	my $msg = "Usage: $0 <srctree> [excludes file]\n";
+	$msg .= "Please provide <srctree>.";
+	$msg .= " Is it '$srctree'?" if $srctree;
+	$msg .= "\n";
+	die $msg;
+}
+my $kconfig_sym_check_excludes = defined $ARGV[0] ? $ARGV[0] : undef;
+
+sub indent_depth {
+	my ($ws) = @_;
+	my $col = 0;
+	for my $c (split //, $ws) {
+		$col = $c eq "\t" ? int($col / 8) * 8 + 8 : $col + 1;
+	}
+	return $col;
+}
+
+my @files = `git -C \Q$srctree\E ls-files '*Kconfig*' 2>/dev/null`;
+if (@files) {
+	chomp @files;
+	@files = map { "$srctree/$_" } @files;
+} else {
+	@files = `find \Q$srctree\E -name '*Kconfig*'`;
+	chomp @files;
+}
+
+@files = grep { !m{/scripts/kconfig/tests/} } @files;
+
+my %configs = ();
+my %refs = ();
+
+foreach my $file (@files) {
+	open F, $file or die "Cannot open $file: $!";
+
+	my $help = 0;
+	my $help_level;
+	my $level;
+
+	while (<F>) {
+		chomp;
+
+		while (/\\\s*$/) {
+			s/\\\s*$/ /;
+			my $cont = <F> // last;
+			chomp $cont;
+			$_ .= $cont;
+		}
+
+		next if /^\s*$/;
+		next if /^\s*#/;
+
+		/^(\s*)/;
+		$level = indent_depth($1);
+
+		if ($help && $level < $help_level) {
+			$help = 0;
+		}
+
+		next if ($help);
+
+		if (/^\s*(help|\-\-\-help\-\-\-)$/) {
+			$help = 1;
+			my $next;
+			while (defined($next = <F>)) {
+				last unless $next =~ /^\s*(?:#.*)?$/;
+			}
+			last unless defined $next;
+			$next =~ /^(\s*)/;
+			if (indent_depth($1) >= $level) {
+				$help_level = indent_depth($1);
+			} else {
+				$help = 0;
+			}
+			$_ = $next;
+			redo;
+		}
+
+		if (/^\s*(config|menuconfig)\s+([a-zA-Z0-9_]+)\s*(#.*)?$/) {
+			$configs{$2}++;
+			next;
+		}
+
+		if (/^\s*(default|def_bool|def_tristate|select|depends\s+on|imply|visible\s+if|range|if|bool|tristate|int|hex|string|prompt)\s+(.+)\s*$/) {
+			my $s = $2;
+			$s =~ s/"(?:[^"\\]|\\.)*"|'(?:[^'\\]|\\.)*'//g;
+			$s =~ s/#.*//;
+			$s =~ s/\$\((?:[^()]*|\((?:[^()]*|\([^()]*\))*\))*\)//g;
+			$s =~ s/%%[^%]*%%//g;
+			my @syms = split /[^a-zA-Z0-9_]+/, $s;
+			map {
+				$refs{$_}++ if (/[a-zA-Z]/ && $_ ne "if" && $_ ne "y" && $_ ne "n" && $_ ne "m" && !/^0[xX][0-9a-fA-F]+$/);
+			} @syms
+		}
+	}
+
+	close F;
+}
+
+my %known_syms = ();
+if (defined $kconfig_sym_check_excludes) {
+	my $file = $kconfig_sym_check_excludes;
+	open(F, "<", $file) or die "Cannot open $file: $!";
+	while (<F>) {
+		chomp;
+		next if /^\s*$/;
+		next if /^\s*#/;
+		$known_syms{$1}++ if (/^\s*([a-zA-Z0-9_]+)\s*(#.*)?$/);
+	}
+}
+
+my $ret = 0;
+foreach my $k (sort keys %refs) {
+	next if (exists $configs{$k} || exists $known_syms{$k});
+
+	print "$k";
+	print " - warning: '$k' is probably not what you want; Kconfig tristate literals are always lowercase ('n', 'y', 'm')" if ($k eq "N" || $k eq "Y" || $k eq "M");
+	print "\n";
+
+	$ret = 1;
+}
+
+exit $ret;