Subject: CVE-2022-48755: powerpc64/bpf: Limit 'ldbrx' to processors compliant with ISA v2.06

From: Greg Kroah-Hartman <[email-masked]>

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

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

powerpc64/bpf: Limit 'ldbrx' to processors compliant with ISA v2.06

Johan reported the below crash with test_bpf on ppc64 e5500:

  test_bpf: #296 ALU_END_FROM_LE 64: 0x0123456789abcdef -> 0x67452301 jited:1
  Oops: Exception in kernel mode, sig: 4 [#1]
  BE PAGE_SIZE=4K SMP NR_CPUS=24 QEMU e500
  Modules linked in: test_bpf(+)
  CPU: 0 PID: 76 Comm: insmod Not tainted 5.14.0-03771-g98c2059e008a-dirty #1
  NIP:  8000000000061c3c LR: 80000000006dea64 CTR: 8000000000061c18
  REGS: c0000000032d3420 TRAP: 0700   Not tainted (5.14.0-03771-g98c2059e008a-dirty)
  MSR:  0000000080089000 <EE,ME>  CR: 88002822  XER: 20000000 IRQMASK: 0
  <...>
  NIP [8000000000061c3c] 0x8000000000061c3c
  LR [80000000006dea64] .__run_one+0x104/0x17c [test_bpf]
  Call Trace:
   .__run_one+0x60/0x17c [test_bpf] (unreliable)
   .test_bpf_init+0x6a8/0xdc8 [test_bpf]
   .do_one_initcall+0x6c/0x28c
   .do_init_module+0x68/0x28c
   .load_module+0x2460/0x2abc
   .__do_sys_init_module+0x120/0x18c
   .system_call_exception+0x110/0x1b8
   system_call_common+0xf0/0x210
  --- interrupt: c00 at 0x101d0acc
  <...>
  ---[ end trace 47b2bf19090bb3d0 ]---

  Illegal instruction

The illegal instruction turned out to be 'ldbrx' emitted for
BPF_FROM_[L|B]E, which was only introduced in ISA v2.06. Guard use of
the same and implement an alternative approach for older processors.

The Linux kernel CVE team has assigned CVE-2022-48755 to this issue.

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

	Issue introduced in 4.8 with commit 156d0e290e96 and fixed in 5.10.96 with commit 129c71829d7f
	Issue introduced in 4.8 with commit 156d0e290e96 and fixed in 5.15.19 with commit 3bfbc00587dc
	Issue introduced in 4.8 with commit 156d0e290e96 and fixed in 5.16.5 with commit aaccfeeee163
	Issue introduced in 4.8 with commit 156d0e290e96 and fixed in 5.17 with commit 3f5f766d5f7f

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-2022-48755
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:
	arch/powerpc/include/asm/ppc-opcode.h
	arch/powerpc/net/bpf_jit_comp64.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/129c71829d7f46423d95c19e8d87ce956d4c6e1c
	https://git.kernel.org/stable/c/3bfbc00587dc883eaed383558ae512a351c2cd09
	https://git.kernel.org/stable/c/aaccfeeee1630b155e8ff0d6c449d3de1ef86e73
	https://git.kernel.org/stable/c/3f5f766d5f7f95a69a630da3544a1a0cee1cdddf