Revision 624f5ab8720b3371367327a822c267699c1823b8 authored by Eric Biggers on 07 November 2017, 22:29:02 UTC, committed by James Morris on 08 November 2017, 13:38:21 UTC
syzkaller reported a NULL pointer dereference in asn1_ber_decoder(). It can be reproduced by the following command, assuming CONFIG_PKCS7_TEST_KEY=y: keyctl add pkcs7_test desc '' @s The bug is that if the data buffer is empty, an integer underflow occurs in the following check: if (unlikely(dp >= datalen - 1)) goto data_overrun_error; This results in the NULL data pointer being dereferenced. Fix it by checking for 'datalen - dp < 2' instead. Also fix the similar check for 'dp >= datalen - n' later in the same function. That one possibly could result in a buffer overread. The NULL pointer dereference was reproducible using the "pkcs7_test" key type but not the "asymmetric" key type because the "asymmetric" key type checks for a 0-length payload before calling into the ASN.1 decoder but the "pkcs7_test" key type does not. The bug report was: BUG: unable to handle kernel NULL pointer dereference at (null) IP: asn1_ber_decoder+0x17f/0xe60 lib/asn1_decoder.c:233 PGD 7b708067 P4D 7b708067 PUD 7b6ee067 PMD 0 Oops: 0000 [#1] SMP Modules linked in: CPU: 0 PID: 522 Comm: syz-executor1 Not tainted 4.14.0-rc8 #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.3-20171021_125229-anatol 04/01/2014 task: ffff9b6b3798c040 task.stack: ffff9b6b37970000 RIP: 0010:asn1_ber_decoder+0x17f/0xe60 lib/asn1_decoder.c:233 RSP: 0018:ffff9b6b37973c78 EFLAGS: 00010216 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000000021c RDX: ffffffff814a04ed RSI: ffffb1524066e000 RDI: ffffffff910759e0 RBP: ffff9b6b37973d60 R08: 0000000000000001 R09: ffff9b6b3caa4180 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f10ed1f2700(0000) GS:ffff9b6b3ea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000007b6f3000 CR4: 00000000000006f0 Call Trace: pkcs7_parse_message+0xee/0x240 crypto/asymmetric_keys/pkcs7_parser.c:139 verify_pkcs7_signature+0x33/0x180 certs/system_keyring.c:216 pkcs7_preparse+0x41/0x70 crypto/asymmetric_keys/pkcs7_key_type.c:63 key_create_or_update+0x180/0x530 security/keys/key.c:855 SYSC_add_key security/keys/keyctl.c:122 [inline] SyS_add_key+0xbf/0x250 security/keys/keyctl.c:62 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x4585c9 RSP: 002b:00007f10ed1f1bd8 EFLAGS: 00000216 ORIG_RAX: 00000000000000f8 RAX: ffffffffffffffda RBX: 00007f10ed1f2700 RCX: 00000000004585c9 RDX: 0000000020000000 RSI: 0000000020008ffb RDI: 0000000020008000 RBP: 0000000000000000 R08: ffffffffffffffff R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000216 R12: 00007fff1b2260ae R13: 00007fff1b2260af R14: 00007f10ed1f2700 R15: 0000000000000000 Code: dd ca ff 48 8b 45 88 48 83 e8 01 4c 39 f0 0f 86 a8 07 00 00 e8 53 dd ca ff 49 8d 46 01 48 89 85 58 ff ff ff 48 8b 85 60 ff ff ff <42> 0f b6 0c 30 89 c8 88 8d 75 ff ff ff 83 e0 1f 89 8d 28 ff ff RIP: asn1_ber_decoder+0x17f/0xe60 lib/asn1_decoder.c:233 RSP: ffff9b6b37973c78 CR2: 0000000000000000 Fixes: 42d5ec27f873 ("X.509: Add an ASN.1 decoder") Reported-by: syzbot <syzkaller@googlegroups.com> Cc: <stable@vger.kernel.org> # v3.7+ Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
1 parent fbc3edf
headerdep.pl
#! /usr/bin/env perl
# SPDX-License-Identifier: GPL-2.0
#
# Detect cycles in the header file dependency graph
# Vegard Nossum <vegardno@ifi.uio.no>
#
use strict;
use warnings;
use Getopt::Long;
my $opt_all;
my @opt_include;
my $opt_graph;
&Getopt::Long::Configure(qw(bundling pass_through));
&GetOptions(
help => \&help,
version => \&version,
all => \$opt_all,
"I=s" => \@opt_include,
graph => \$opt_graph,
);
push @opt_include, 'include';
my %deps = ();
my %linenos = ();
my @headers = grep { strip($_) } @ARGV;
parse_all(@headers);
if($opt_graph) {
graph();
} else {
detect_cycles(@headers);
}
sub help {
print "Usage: $0 [options] file...\n";
print "\n";
print "Options:\n";
print " --all\n";
print " --graph\n";
print "\n";
print " -I includedir\n";
print "\n";
print "To make nice graphs, try:\n";
print " $0 --graph include/linux/kernel.h | dot -Tpng -o graph.png\n";
exit;
}
sub version {
print "headerdep version 2\n";
exit;
}
# Get a file name that is relative to our include paths
sub strip {
my $filename = shift;
for my $i (@opt_include) {
my $stripped = $filename;
$stripped =~ s/^$i\///;
return $stripped if $stripped ne $filename;
}
return $filename;
}
# Search for the file name in the list of include paths
sub search {
my $filename = shift;
return $filename if -f $filename;
for my $i (@opt_include) {
my $path = "$i/$filename";
return $path if -f $path;
}
return;
}
sub parse_all {
# Parse all the headers.
my @queue = @_;
while(@queue) {
my $header = pop @queue;
next if exists $deps{$header};
$deps{$header} = [] unless exists $deps{$header};
my $path = search($header);
next unless $path;
open(my $file, '<', $path) or die($!);
chomp(my @lines = <$file>);
close($file);
for my $i (0 .. $#lines) {
my $line = $lines[$i];
if(my($dep) = ($line =~ m/^#\s*include\s*<(.*?)>/)) {
push @queue, $dep;
push @{$deps{$header}}, [$i + 1, $dep];
}
}
}
}
sub print_cycle {
# $cycle[n] includes $cycle[n + 1];
# $cycle[-1] will be the culprit
my $cycle = shift;
# Adjust the line numbers
for my $i (0 .. $#$cycle - 1) {
$cycle->[$i]->[0] = $cycle->[$i + 1]->[0];
}
$cycle->[-1]->[0] = 0;
my $first = shift @$cycle;
my $last = pop @$cycle;
my $msg = "In file included";
printf "%s from %s,\n", $msg, $last->[1] if defined $last;
for my $header (reverse @$cycle) {
printf "%s from %s:%d%s\n",
" " x length $msg,
$header->[1], $header->[0],
$header->[1] eq $last->[1] ? ' <-- here' : '';
}
printf "%s:%d: warning: recursive header inclusion\n",
$first->[1], $first->[0];
}
# Find and print the smallest cycle starting in the specified node.
sub detect_cycles {
my @queue = map { [[0, $_]] } @_;
while(@queue) {
my $top = pop @queue;
my $name = $top->[-1]->[1];
for my $dep (@{$deps{$name}}) {
my $chain = [@$top, [$dep->[0], $dep->[1]]];
# If the dep already exists in the chain, we have a
# cycle...
if(grep { $_->[1] eq $dep->[1] } @$top) {
print_cycle($chain);
next if $opt_all;
return;
}
push @queue, $chain;
}
}
}
sub mangle {
$_ = shift;
s/\//__/g;
s/\./_/g;
s/-/_/g;
$_;
}
# Output dependency graph in GraphViz language.
sub graph {
print "digraph {\n";
print "\t/* vertices */\n";
for my $header (keys %deps) {
printf "\t%s [label=\"%s\"];\n",
mangle($header), $header;
}
print "\n";
print "\t/* edges */\n";
for my $header (keys %deps) {
for my $dep (@{$deps{$header}}) {
printf "\t%s -> %s;\n",
mangle($header), mangle($dep->[1]);
}
}
print "}\n";
}
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