linux-stable.git/lib/test_bpf.c, branch v4.9.91

bpf: introduce BPF_JIT_ALWAYS_ON config

2018-01-31T11:55:56+00:00

[ upstream commit 290af86629b25ffd1ed6232c4e9107da031705cb ]

The BPF interpreter has been used as part of the spectre 2 attack CVE-2017-5715.

A quote from goolge project zero blog:
"At this point, it would normally be necessary to locate gadgets in
the host kernel code that can be used to actually leak data by reading
from an attacker-controlled location, shifting and masking the result
appropriately and then using the result of that as offset to an
attacker-controlled address for a load. But piecing gadgets together
and figuring out which ones work in a speculation context seems annoying.
So instead, we decided to use the eBPF interpreter, which is built into
the host kernel - while there is no legitimate way to invoke it from inside
a VM, the presence of the code in the host kernel's text section is sufficient
to make it usable for the attack, just like with ordinary ROP gadgets."

To make attacker job harder introduce BPF_JIT_ALWAYS_ON config
option that removes interpreter from the kernel in favor of JIT-only mode.
So far eBPF JIT is supported by:
x64, arm64, arm32, sparc64, s390, powerpc64, mips64

The start of JITed program is randomized and code page is marked as read-only.
In addition "constant blinding" can be turned on with net.core.bpf_jit_harden

v2->v3:
- move __bpf_prog_ret0 under ifdef (Daniel)

v1->v2:
- fix init order, test_bpf and cBPF (Daniel's feedback)
- fix offloaded bpf (Jakub's feedback)
- add 'return 0' dummy in case something can invoke prog->bpf_func
- retarget bpf tree. For bpf-next the patch would need one extra hunk.
  It will be sent when the trees are merged back to net-next

Considered doing:
  int bpf_jit_enable __read_mostly = BPF_EBPF_JIT_DEFAULT;
but it seems better to land the patch as-is and in bpf-next remove
bpf_jit_enable global variable from all JITs, consolidate in one place
and remove this jit_init() function.

Signed-off-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann 
Signed-off-by: Greg Kroah-Hartman

bpf, arm64: fix jit branch offset related to ldimm64

2017-05-14T12:00:21+00:00

[ Upstream commit ddc665a4bb4b728b4e6ecec8db1b64efa9184b9c ]

When the instruction right before the branch destination is
a 64 bit load immediate, we currently calculate the wrong
jump offset in the ctx->offset[] array as we only account
one instruction slot for the 64 bit load immediate although
it uses two BPF instructions. Fix it up by setting the offset
into the right slot after we incremented the index.

Before (ldimm64 test 1):

  [...]
  00000020:  52800007  mov w7, #0x0 // #0
  00000024:  d2800060  mov x0, #0x3 // #3
  00000028:  d2800041  mov x1, #0x2 // #2
  0000002c:  eb01001f  cmp x0, x1
  00000030:  54ffff82  b.cs 0x00000020
  00000034:  d29fffe7  mov x7, #0xffff // #65535
  00000038:  f2bfffe7  movk x7, #0xffff, lsl #16
  0000003c:  f2dfffe7  movk x7, #0xffff, lsl #32
  00000040:  f2ffffe7  movk x7, #0xffff, lsl #48
  00000044:  d29dddc7  mov x7, #0xeeee // #61166
  00000048:  f2bdddc7  movk x7, #0xeeee, lsl #16
  0000004c:  f2ddddc7  movk x7, #0xeeee, lsl #32
  00000050:  f2fdddc7  movk x7, #0xeeee, lsl #48
  [...]

After (ldimm64 test 1):

  [...]
  00000020:  52800007  mov w7, #0x0 // #0
  00000024:  d2800060  mov x0, #0x3 // #3
  00000028:  d2800041  mov x1, #0x2 // #2
  0000002c:  eb01001f  cmp x0, x1
  00000030:  540000a2  b.cs 0x00000044
  00000034:  d29fffe7  mov x7, #0xffff // #65535
  00000038:  f2bfffe7  movk x7, #0xffff, lsl #16
  0000003c:  f2dfffe7  movk x7, #0xffff, lsl #32
  00000040:  f2ffffe7  movk x7, #0xffff, lsl #48
  00000044:  d29dddc7  mov x7, #0xeeee // #61166
  00000048:  f2bdddc7  movk x7, #0xeeee, lsl #16
  0000004c:  f2ddddc7  movk x7, #0xeeee, lsl #32
  00000050:  f2fdddc7  movk x7, #0xeeee, lsl #48
  [...]

Also, add a couple of test cases to make sure JITs pass
this test. Tested on Cavium ThunderX ARMv8. The added
test cases all pass after the fix.

Fixes: 8eee539ddea0 ("arm64: bpf: fix out-of-bounds read in bpf2a64_offset()")
Reported-by: David S. Miller 
Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Cc: Xi Wang 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

bpf, test: fix ld_abs + vlan push/pop stress test

2016-10-20T18:39:06+00:00

After commit 636c2628086e ("net: skbuff: Remove errornous length
validation in skb_vlan_pop()") mentioned test case stopped working,
throwing a -12 (ENOMEM) return code. The issue however is not due to
636c2628086e, but rather due to a buggy test case that got uncovered
from the change in behaviour in 636c2628086e.

The data_size of that test case for the skb was set to 1. In the
bpf_fill_ld_abs_vlan_push_pop() handler bpf insns are generated that
loop with: reading skb data, pushing 68 tags, reading skb data,
popping 68 tags, reading skb data, etc, in order to force a skb
expansion and thus trigger that JITs recache skb->data. Problem is
that initial data_size is too small.

While before 636c2628086e, the test silently bailed out due to the
skb->len < VLAN_ETH_HLEN check with returning 0, and now throwing an
error from failing skb_ensure_writable(). Set at least minimum of
ETH_HLEN as an initial length so that on first push of data, equivalent
pop will succeed.

Fixes: 4d9c5c53ac99 ("test_bpf: add bpf_skb_vlan_push/pop() tests")
Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

test_bpf: fix the dummy skb after dissector changes

2016-09-15T23:17:15+00:00

Commit d5709f7ab776 ("flow_dissector: For stripped vlan, get vlan
info from skb->vlan_tci") made flow dissector look at vlan_proto
when vlan is present.  Since test_bpf sets skb->vlan_tci to ~0
(including VLAN_TAG_PRESENT) we have to populate skb->vlan_proto.

Fixes false negative on test #24:
test_bpf: #24 LD_PAYLOAD_OFF jited:0 175 ret 0 != 42 FAIL (1 times)

Signed-off-by: Jakub Kicinski 
Reviewed-by: Dinan Gunawardena 
Acked-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: prepare bpf_int_jit_compile/bpf_prog_select_runtime apis

2016-05-16T17:49:32+00:00

Since the blinding is strictly only called from inside eBPF JITs,
we need to change signatures for bpf_int_jit_compile() and
bpf_prog_select_runtime() first in order to prepare that the
eBPF program we're dealing with can change underneath. Hence,
for call sites, we need to return the latest prog. No functional
change in this patch.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

lib/test_bpf: Add additional BPF_ADD tests

2016-04-06T20:47:51+00:00

Some of these tests proved useful with the powerpc eBPF JIT port due to
sign-extended 16-bit immediate loads. Though some of these aspects get
covered in other tests, it is better to have explicit tests so as to
quickly tag the precise problem.

Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: "David S. Miller" 
Cc: Ananth N Mavinakayanahalli 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Signed-off-by: Naveen N. Rao 
Acked-by: Alexei Starovoitov 
Acked-by: Daniel Borkmann 
Signed-off-by: David S. Miller

lib/test_bpf: Add test to check for result of 32-bit add that overflows

2016-04-06T20:47:51+00:00

BPF_ALU32 and BPF_ALU64 tests for adding two 32-bit values that results in
32-bit overflow.

Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: "David S. Miller" 
Cc: Ananth N Mavinakayanahalli 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Signed-off-by: Naveen N. Rao 
Acked-by: Alexei Starovoitov 
Acked-by: Daniel Borkmann 
Signed-off-by: David S. Miller

lib/test_bpf: Add tests for unsigned BPF_JGT

2016-04-06T20:47:51+00:00

Unsigned Jump-if-Greater-Than.

Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: "David S. Miller" 
Cc: Ananth N Mavinakayanahalli 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Signed-off-by: Naveen N. Rao 
Acked-by: Alexei Starovoitov 
Acked-by: Daniel Borkmann 
Signed-off-by: David S. Miller

lib/test_bpf: Fix JMP_JSET tests

2016-04-06T20:47:50+00:00

JMP_JSET tests incorrectly used BPF_JNE. Fix the same.

Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: "David S. Miller" 
Cc: Ananth N Mavinakayanahalli 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Signed-off-by: Naveen N. Rao 
Acked-by: Alexei Starovoitov 
Acked-by: Daniel Borkmann 
Signed-off-by: David S. Miller

bpf, test: add couple of test cases

2015-12-18T21:04:51+00:00

Add couple of test cases for interpreter but also JITs, f.e. to test that
when imm32 moves are being done, upper 32bits of the regs are being zero
extended.

Without JIT:

  [...]
  [ 1114.129301] test_bpf: #43 MOV REG64 jited:0 128 PASS
  [ 1114.130626] test_bpf: #44 MOV REG32 jited:0 139 PASS
  [ 1114.132055] test_bpf: #45 LD IMM64 jited:0 124 PASS
  [...]

With JIT (generated code can as usual be nicely verified with the help of
bpf_jit_disasm tool):

  [...]
  [ 1062.726782] test_bpf: #43 MOV REG64 jited:1 6 PASS
  [ 1062.726890] test_bpf: #44 MOV REG32 jited:1 6 PASS
  [ 1062.726993] test_bpf: #45 LD IMM64 jited:1 6 PASS
  [...]

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller