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, 98 insertions, 0 deletions

diff --git a/scripts/checkincludes.pl b/scripts/checkincludes.pl
new file mode 100755
index 000000000..b514a956d
--- /dev/null
+++ b/scripts/checkincludes.pl
@@ -0,0 +1,98 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+# checkincludes: find/remove files included more than once
+#
+# Copyright abandoned, 2000, Niels Kristian Bech Jensen <nkbj@image.dk>.
+# Copyright 2009 Luis R. Rodriguez <mcgrof@gmail.com>
+#
+# This script checks for duplicate includes. It also has support
+# to remove them in place. Note that this will not take into
+# consideration macros so you should run this only if you know
+# you do have real dups and do not have them under #ifdef's. You
+# could also just review the results.
+
+use strict;
+
+sub usage {
+	print "Usage: checkincludes.pl [-r]\n";
+	print "By default we just warn of duplicates\n";
+	print "To remove duplicated includes in place use -r\n";
+	exit 1;
+}
+
+my $remove = 0;
+
+if ($#ARGV < 0) {
+	usage();
+}
+
+if ($#ARGV >= 1) {
+	if ($ARGV[0] =~ /^-/) {
+		if ($ARGV[0] eq "-r") {
+			$remove = 1;
+			shift;
+		} else {
+			usage();
+		}
+	}
+}
+
+my $dup_counter = 0;
+
+foreach my $file (@ARGV) {
+	open(my $f, '<', $file)
+	    or die "Cannot open $file: $!.\n";
+
+	my %includedfiles = ();
+	my @file_lines = ();
+
+	while (<$f>) {
+		if (m/^\s*#\s*include\s*[<"](\S*)[>"]/o) {
+			++$includedfiles{$1};
+		}
+		push(@file_lines, $_);
+	}
+
+	close($f);
+
+	if (!$remove) {
+		foreach my $filename (keys %includedfiles) {
+			if ($includedfiles{$filename} > 1) {
+				print "$file: $filename is included more than once.\n";
+				++$dup_counter;
+			}
+		}
+		next;
+	}
+
+	open($f, '>', $file)
+	    or die("Cannot write to $file: $!");
+
+	my $dups = 0;
+	foreach (@file_lines) {
+		if (m/^\s*#\s*include\s*[<"](\S*)[>"]/o) {
+			foreach my $filename (keys %includedfiles) {
+				if ($1 eq $filename) {
+					if ($includedfiles{$filename} > 1) {
+						$includedfiles{$filename}--;
+						$dups++;
+						++$dup_counter;
+					} else {
+						print {$f} $_;
+					}
+				}
+			}
+		} else {
+			print {$f} $_;
+		}
+	}
+	if ($dups > 0) {
+		print "$file: removed $dups duplicate includes\n";
+	}
+	close($f);
+}
+
+if ($dup_counter == 0) {
+	print "No duplicate includes found.\n";
+}