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linux/tools/testing/selftests/bpf
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Daniel Borkmann 6bdf6abc56 bpf: prevent leaking pointer via xadd on unpriviledged 
Leaking kernel addresses on unpriviledged is generally disallowed,
for example, verifier rejects the following:

  0: (b7) r0 = 0
  1: (18) r2 = 0xffff897e82304400
  3: (7b) *(u64 *)(r1 +48) = r2
  R2 leaks addr into ctx

Doing pointer arithmetic on them is also forbidden, so that they
don't turn into unknown value and then get leaked out. However,
there's xadd as a special case, where we don't check the src reg
for being a pointer register, e.g. the following will pass:

  0: (b7) r0 = 0
  1: (7b) *(u64 *)(r1 +48) = r0
  2: (18) r2 = 0xffff897e82304400 ; map
  4: (db) lock *(u64 *)(r1 +48) += r2
  5: (95) exit

We could store the pointer into skb->cb, loose the type context,
and then read it out from there again to leak it eventually out
of a map value. Or more easily in a different variant, too:

   0: (bf) r6 = r1
   1: (7a) *(u64 *)(r10 -8) = 0
   2: (bf) r2 = r10
   3: (07) r2 += -8
   4: (18) r1 = 0x0
   6: (85) call bpf_map_lookup_elem#1
   7: (15) if r0 == 0x0 goto pc+3
   R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R6=ctx R10=fp
   8: (b7) r3 = 0
   9: (7b) *(u64 *)(r0 +0) = r3
  10: (db) lock *(u64 *)(r0 +0) += r6
  11: (b7) r0 = 0
  12: (95) exit

  from 7 to 11: R0=inv,min_value=0,max_value=0 R6=ctx R10=fp
  11: (b7) r0 = 0
  12: (95) exit

Prevent this by checking xadd src reg for pointer types. Also
add a couple of test cases related to this.

Fixes: 1be7f75d16 ("bpf: enable non-root eBPF programs")
Fixes: 17a5267067 ("bpf: verifier (add verifier core)")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-06-29 15:44:34 -04:00
..
gnu selftests/bpf: get rid of -D__x86_64__ 2017-05-03 09:51:25 -04:00
include/uapi/linux selftests/bpf: fix broken build due to types.h 2017-05-17 18:45:14 -04:00
.gitignore bpf: Add test_tag to .gitignore 2017-02-10 15:56:08 -05:00
bpf_endian.h bpf, tests: fix endianness selection 2017-06-08 16:17:29 -04:00
bpf_util.h bpf: Move endianness BPF helpers out of bpf_util.h 2017-05-01 12:43:49 -07:00
config
Makefile bpf: Provide a linux/types.h override for bpf selftests. 2017-05-11 12:00:50 -07:00
test_align.c bpf: Handle multiple variable additions into packet pointers in verifier. 2017-05-11 19:48:58 -07:00
test_iptunnel_common.h selftests/bpf: add a test for basic XDP functionality 2017-04-01 12:45:57 -07:00
test_kmod.sh selftests: do not require bash to run bpf tests 2017-01-05 13:19:47 -07:00
test_l4lb.c bpf: Move endianness BPF helpers out of bpf_util.h 2017-05-01 12:43:49 -07:00
test_lpm_map.c bpf: Remove bpf_sys.h from selftests 2017-02-10 15:56:08 -05:00
test_lru_map.c bpf: lru: Lower the PERCPU_NR_SCANS from 16 to 4 2017-04-17 13:55:52 -04:00
test_maps.c bpf: provide a generic macro for percpu values for selftests 2017-04-28 15:48:15 -04:00
test_pkt_access.c selftests/bpf: fix broken build due to types.h 2017-05-17 18:45:14 -04:00
test_progs.c selftests/bpf: add a test case to check verifier pointer arithmetic 2017-05-03 09:51:25 -04:00
test_tag.c bpf: Remove bpf_sys.h from selftests 2017-02-10 15:56:08 -05:00
test_tcp_estats.c selftests/bpf: add a test case to check verifier pointer arithmetic 2017-05-03 09:51:25 -04:00
test_verifier.c bpf: prevent leaking pointer via xadd on unpriviledged 2017-06-29 15:44:34 -04:00
test_xdp.c selftests: bpf: Use bpf_endian.h in test_xdp.c 2017-05-02 07:52:01 -07:00