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Eric Biggers 624f5ab872 KEYS: fix NULL pointer dereference during ASN.1 parsing [ver #2]
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: 42d5ec27f8 ("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>
2017-11-09 00:38:21 +11:00
arch Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-11-06 09:05:03 -08:00
block License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-11-06 09:05:03 -08:00
Documentation Documentation: enforcement-statement: name updates 2017-11-05 10:21:06 -08:00
drivers drivers/ide-cd: Handle missing driver data during status check gracefully 2017-11-07 09:12:04 -08:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs fs/hugetlbfs/inode.c: fix hwpoison reserve accounting 2017-11-03 07:39:19 -07:00
include Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-11-05 11:44:39 -08:00
init License cleanup: add SPDX license identifiers to some files 2017-11-02 10:04:46 -07:00
ipc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kernel Merge branch 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2017-11-06 12:26:49 -08:00
lib KEYS: fix NULL pointer dereference during ASN.1 parsing [ver #2] 2017-11-09 00:38:21 +11:00
mm mm, swap: fix race between swap count continuation operations 2017-11-03 07:39:19 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-11-03 09:09:21 -07:00
samples License cleanup: add SPDX license identifiers to some files 2017-11-02 10:04:46 -07:00
scripts scripts: add leaking_addresses.pl 2017-11-06 11:46:42 -08:00
security License cleanup: add SPDX license identifiers to some files 2017-11-02 10:04:46 -07:00
sound License cleanup: add SPDX license identifiers to some files 2017-11-02 10:04:46 -07:00
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-11-05 11:44:39 -08:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt Fixes for interrupt controller emulation in ARM/ARM64 and x86, plus a one-liner 2017-11-04 11:44:55 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap Update MIPS email addresses 2017-11-03 09:02:30 -07:00
COPYING
CREDITS selinux/stable-4.14 PR 20170831 2017-09-12 13:21:00 -07:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS scripts: add leaking_addresses.pl 2017-11-06 11:46:42 -08:00
Makefile Linux 4.14-rc8 2017-11-05 13:05:14 -08:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

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See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
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