linux-stable.git/tools/testing/selftests/bpf, branch v4.15

bpf: mark dst unknown on inconsistent {s, u}bounds adjustments

2018-01-18T00:23:17+00:00

syzkaller generated a BPF proglet and triggered a warning with
the following:

  0: (b7) r0 = 0
  1: (d5) if r0 s<= 0x0 goto pc+0
   R0=inv0 R1=ctx(id=0,off=0,imm=0) R10=fp0
  2: (1f) r0 -= r1
   R0=inv0 R1=ctx(id=0,off=0,imm=0) R10=fp0
  verifier internal error: known but bad sbounds

What happens is that in the first insn, r0's min/max value
are both 0 due to the immediate assignment, later in the jsle
test the bounds are updated for the min value in the false
path, meaning, they yield smin_val = 1, smax_val = 0, and when
ctx pointer is subtracted from r0, verifier bails out with the
internal error and throwing a WARN since smin_val != smax_val
for the known constant.

For min_val > max_val scenario it means that reg_set_min_max()
and reg_set_min_max_inv() (which both refine existing bounds)
demonstrated that such branch cannot be taken at runtime.

In above scenario for the case where it will be taken, the
existing [0, 0] bounds are kept intact. Meaning, the rejection
is not due to a verifier internal error, and therefore the
WARN() is not necessary either.

We could just reject such cases in adjust_{ptr,scalar}_min_max_vals()
when either known scalars have smin_val != smax_val or
umin_val != umax_val or any scalar reg with bounds
smin_val > smax_val or umin_val > umax_val. However, there
may be a small risk of breakage of buggy programs, so handle
this more gracefully and in adjust_{ptr,scalar}_min_max_vals()
just taint the dst reg as unknown scalar when we see ops with
such kind of src reg.

Reported-by: syzbot+6d362cadd45dc0a12ba4@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann 
Signed-off-by: Alexei Starovoitov

bpf: reject stores into ctx via st and xadd

2018-01-16T23:04:58+00:00

Alexei found that verifier does not reject stores into context
via BPF_ST instead of BPF_STX. And while looking at it, we
also should not allow XADD variant of BPF_STX.

The context rewriter is only assuming either BPF_LDX_MEM- or
BPF_STX_MEM-type operations, thus reject anything other than
that so that assumptions in the rewriter properly hold. Add
test cases as well for BPF selftests.

Fixes: d691f9e8d440 ("bpf: allow programs to write to certain skb fields")
Reported-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann 
Signed-off-by: Alexei Starovoitov

bpf: arsh is not supported in 32 bit alu thus reject it

2018-01-10T22:42:22+00:00

The following snippet was throwing an 'unknown opcode cc' warning
in BPF interpreter:

  0: (18) r0 = 0x0
  2: (7b) *(u64 *)(r10 -16) = r0
  3: (cc) (u32) r0 s>>= (u32) r0
  4: (95) exit

Although a number of JITs do support BPF_ALU | BPF_ARSH | BPF_{K,X}
generation, not all of them do and interpreter does neither. We can
leave existing ones and implement it later in bpf-next for the
remaining ones, but reject this properly in verifier for the time
being.

Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)")
Reported-by: syzbot+93c4904c5c70348a6890@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann 
Signed-off-by: Alexei Starovoitov

selftests/bpf: fix test_align

2018-01-06T23:10:32+00:00

since commit 82abbf8d2fc4 the verifier rejects the bit-wise
arithmetic on pointers earlier.
The test 'dubious pointer arithmetic' now has less output to match on.
Adjust it.

Fixes: 82abbf8d2fc4 ("bpf: do not allow root to mangle valid pointers")
Reported-by: kernel test robot 
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann

selftests/bpf: fix Makefile for passing LLC to the command line

2017-12-21T23:54:31+00:00

Makefile has a LLC variable that is initialised to "llc", but can
theoretically be overridden from the command line ("make LLC=llc-6.0").
However, this fails because for LLVM probe check, "llc" is called
directly. Use the $(LLC) variable instead to fix this.

Fixes: 22c8852624fc ("bpf: improve selftests and add tests for meta pointer")
Signed-off-by: Quentin Monnet 
Signed-off-by: Jakub Kicinski 
Signed-off-by: Daniel Borkmann

bpf: do not allow root to mangle valid pointers

2017-12-21T01:26:29+00:00

Do not allow root to convert valid pointers into unknown scalars.
In particular disallow:
 ptr &= reg
 ptr <<= reg
 ptr += ptr
and explicitly allow:
 ptr -= ptr
since pkt_end - pkt == length

1.
This minimizes amount of address leaks root can do.
In the future may need to further tighten the leaks with kptr_restrict.

2.
If program has such pointer math it's likely a user mistake and
when verifier complains about it right away instead of many instructions
later on invalid memory access it's easier for users to fix their progs.

3.
when register holding a pointer cannot change to scalar it allows JITs to
optimize better. Like 32-bit archs could use single register for pointers
instead of a pair required to hold 64-bit scalars.

4.
reduces architecture dependent behavior. Since code:
r1 = r10;
r1 &= 0xff;
if (r1 ...)
will behave differently arm64 vs x64 and offloaded vs native.

A significant chunk of ptr mangling was allowed by
commit f1174f77b50c ("bpf/verifier: rework value tracking")
yet some of it was allowed even earlier.

Signed-off-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann

selftests/bpf: add tests for recent bugfixes

2017-12-21T01:15:41+00:00

These tests should cover the following cases:

 - MOV with both zero-extended and sign-extended immediates
 - implicit truncation of register contents via ALU32/MOV32
 - implicit 32-bit truncation of ALU32 output
 - oversized register source operand for ALU32 shift
 - right-shift of a number that could be positive or negative
 - map access where adding the operation size to the offset causes signed
   32-bit overflow
 - direct stack access at a ~4GiB offset

Also remove the F_LOAD_WITH_STRICT_ALIGNMENT flag from a bunch of tests
that should fail independent of what flags userspace passes.

Signed-off-by: Jann Horn 
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann

bpf: Fix tools and testing build.

2017-12-19T23:15:05+00:00

I'm getting various build failures on sparc64.  The key is
usually that the userland tools get built 32-bit.

1) clock_gettime() is in librt, so that must be added to the link
   libraries.

2) "sizeof(x)" must be printed with "%Z" printf prefix.

Signed-off-by: David S. Miller 
Signed-off-by: Daniel Borkmann

bpf: add test case for ld_abs and helper changing pkt data

2017-12-15T17:19:36+00:00

Add a test that i) uses LD_ABS, ii) zeroing R6 before call, iii) calls
a helper that triggers reload of cached skb data, iv) uses LD_ABS again.
It's added for test_bpf in order to do runtime testing after JITing as
well as test_verifier to test that the sequence is allowed.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: Alexei Starovoitov

bpf: fix broken BPF selftest build

2017-12-12T17:51:12+00:00

At least on x86_64, the kernel's BPF selftests seemed to have stopped
to build due to 618e165b2a8e ("selftests/bpf: sync kernel headers and
introduce arch support in Makefile"):

  [...]
  In file included from test_verifier.c:29:0:
  ../../../include/uapi/linux/bpf_perf_event.h:11:32:
     fatal error: asm/bpf_perf_event.h: No such file or directory
   #include 
                                ^
  compilation terminated.
  [...]

While pulling in tools/arch/*/include/uapi/asm/bpf_perf_event.h seems
to work fine, there's no automated fall-back logic right now that would
do the same out of tools/include/uapi/asm-generic/bpf_perf_event.h. The
usual convention today is to add a include/[uapi/]asm/ equivalent that
would pull in the correct arch header or generic one as fall-back, all
ifdef'ed based on compiler target definition. It's similarly done also
in other cases such as tools/include/asm/barrier.h, thus adapt the same
here.

Fixes: 618e165b2a8e ("selftests/bpf: sync kernel headers and introduce arch support in Makefile")
Signed-off-by: Daniel Borkmann 
Cc: Hendrik Brueckner 
Cc: Arnaldo Carvalho de Melo 
Acked-by: Alexei Starovoitov 
Signed-off-by: Alexei Starovoitov