cve/published/2022/CVE-2022-49228.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2022-49228: bpf: Fix a btf decl_tag bug when tagging a function

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix a btf decl_tag bug when tagging a function

syzbot reported a btf decl_tag bug with stack trace below:

  general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
  CPU: 0 PID: 3592 Comm: syz-executor914 Not tainted 5.16.0-syzkaller-11424-gb7892f7d5cb2 #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:btf_type_vlen include/linux/btf.h:231 [inline]
  RIP: 0010:btf_decl_tag_resolve+0x83e/0xaa0 kernel/bpf/btf.c:3910
  ...
  Call Trace:
   <TASK>
   btf_resolve+0x251/0x1020 kernel/bpf/btf.c:4198
   btf_check_all_types kernel/bpf/btf.c:4239 [inline]
   btf_parse_type_sec kernel/bpf/btf.c:4280 [inline]
   btf_parse kernel/bpf/btf.c:4513 [inline]
   btf_new_fd+0x19fe/0x2370 kernel/bpf/btf.c:6047
   bpf_btf_load kernel/bpf/syscall.c:4039 [inline]
   __sys_bpf+0x1cbb/0x5970 kernel/bpf/syscall.c:4679
   __do_sys_bpf kernel/bpf/syscall.c:4738 [inline]
   __se_sys_bpf kernel/bpf/syscall.c:4736 [inline]
   __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4736
   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
   do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
   entry_SYSCALL_64_after_hwframe+0x44/0xae

The kasan error is triggered with an illegal BTF like below:
   type 0: void
   type 1: int
   type 2: decl_tag to func type 3
   type 3: func to func_proto type 8
The total number of types is 4 and the type 3 is illegal
since its func_proto type is out of range.

Currently, the target type of decl_tag can be struct/union, var or func.
Both struct/union and var implemented their own 'resolve' callback functions
and hence handled properly in kernel.
But func type doesn't have 'resolve' callback function. When
btf_decl_tag_resolve() tries to check func type, it tries to get
vlen of its func_proto type, which triggered the above kasan error.

To fix the issue, btf_decl_tag_resolve() needs to do btf_func_check()
before trying to accessing func_proto type.
In the current implementation, func type is checked with
btf_func_check() in the main checking function btf_check_all_types().
To fix the above kasan issue, let us implement 'resolve' callback
func type properly. The 'resolve' callback will be also called
in btf_check_all_types() for func types.

The Linux kernel CVE team has assigned CVE-2022-49228 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.16 with commit b5ea834dde6b6e7f75e51d5f66dac8cd7c97b5ef and fixed in 5.16.19 with commit a3bcd2110c087bc62e90fddd4a93237b049d6e68
	Issue introduced in 5.16 with commit b5ea834dde6b6e7f75e51d5f66dac8cd7c97b5ef and fixed in 5.17.2 with commit 796d5666f6422ddadc938fb888044fcc16f2dbe3
	Issue introduced in 5.16 with commit b5ea834dde6b6e7f75e51d5f66dac8cd7c97b5ef and fixed in 5.18 with commit d7e7b42f4f956f2c68ad8cda87d750093dbba737

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-49228
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	kernel/bpf/btf.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/a3bcd2110c087bc62e90fddd4a93237b049d6e68
	https://git.kernel.org/stable/c/796d5666f6422ddadc938fb888044fcc16f2dbe3
	https://git.kernel.org/stable/c/d7e7b42f4f956f2c68ad8cda87d750093dbba737