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Daniel Borkmann 37c9e3ee42 bpf: fix inner map masking to prevent oob under speculation 
[ commit 9d5564ddcf upstream ]

During review I noticed that inner meta map setup for map in
map is buggy in that it does not propagate all needed data
from the reference map which the verifier is later accessing.

In particular one such case is index masking to prevent out of
bounds access under speculative execution due to missing the
map's unpriv_array/index_mask field propagation. Fix this such
that the verifier is generating the correct code for inlined
lookups in case of unpriviledged use.

Before patch (test_verifier's 'map in map access' dump):

  # bpftool prog dump xla id 3
     0: (62) *(u32 *)(r10 -4) = 0
     1: (bf) r2 = r10
     2: (07) r2 += -4
     3: (18) r1 = map[id:4]
     5: (07) r1 += 272                |
     6: (61) r0 = *(u32 *)(r2 +0)     |
     7: (35) if r0 >= 0x1 goto pc+6   | Inlined map in map lookup
     8: (54) (u32) r0 &= (u32) 0      | with index masking for
     9: (67) r0 <<= 3                 | map->unpriv_array.
    10: (0f) r0 += r1                 |
    11: (79) r0 = *(u64 *)(r0 +0)     |
    12: (15) if r0 == 0x0 goto pc+1   |
    13: (05) goto pc+1                |
    14: (b7) r0 = 0                   |
    15: (15) if r0 == 0x0 goto pc+11
    16: (62) *(u32 *)(r10 -4) = 0
    17: (bf) r2 = r10
    18: (07) r2 += -4
    19: (bf) r1 = r0
    20: (07) r1 += 272                |
    21: (61) r0 = *(u32 *)(r2 +0)     | Index masking missing (!)
    22: (35) if r0 >= 0x1 goto pc+3   | for inner map despite
    23: (67) r0 <<= 3                 | map->unpriv_array set.
    24: (0f) r0 += r1                 |
    25: (05) goto pc+1                |
    26: (b7) r0 = 0                   |
    27: (b7) r0 = 0
    28: (95) exit

After patch:

  # bpftool prog dump xla id 1
     0: (62) *(u32 *)(r10 -4) = 0
     1: (bf) r2 = r10
     2: (07) r2 += -4
     3: (18) r1 = map[id:2]
     5: (07) r1 += 272                |
     6: (61) r0 = *(u32 *)(r2 +0)     |
     7: (35) if r0 >= 0x1 goto pc+6   | Same inlined map in map lookup
     8: (54) (u32) r0 &= (u32) 0      | with index masking due to
     9: (67) r0 <<= 3                 | map->unpriv_array.
    10: (0f) r0 += r1                 |
    11: (79) r0 = *(u64 *)(r0 +0)     |
    12: (15) if r0 == 0x0 goto pc+1   |
    13: (05) goto pc+1                |
    14: (b7) r0 = 0                   |
    15: (15) if r0 == 0x0 goto pc+12
    16: (62) *(u32 *)(r10 -4) = 0
    17: (bf) r2 = r10
    18: (07) r2 += -4
    19: (bf) r1 = r0
    20: (07) r1 += 272                |
    21: (61) r0 = *(u32 *)(r2 +0)     |
    22: (35) if r0 >= 0x1 goto pc+4   | Now fixed inlined inner map
    23: (54) (u32) r0 &= (u32) 0      | lookup with proper index masking
    24: (67) r0 <<= 3                 | for map->unpriv_array.
    25: (0f) r0 += r1                 |
    26: (05) goto pc+1                |
    27: (b7) r0 = 0                   |
    28: (b7) r0 = 0
    29: (95) exit

Fixes: b2157399cc ("bpf: prevent out-of-bounds speculation")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-01-31 08:14:41 +01:00
..
arraymap.c bpf: decouple btf from seq bpf fs dump and enable more maps 2018-08-13 00:52:45 +02:00
bpf_lru_list.c bpf: lru: Lower the PERCPU_NR_SCANS from 16 to 4 2017-04-17 13:55:52 -04:00
bpf_lru_list.h bpf: Only set node->ref = 1 if it has not been set 2017-09-01 09:57:39 -07:00
btf.c bpf: btf: Fix end boundary calculation for type section 2018-09-12 22:00:23 +02:00
cgroup.c bpf: introduce update_effective_progs() 2018-08-07 14:29:55 +02:00
core.c bpf: enable access to ax register also from verifier rewrite 2019-01-31 08:14:40 +01:00
cpumap.c bpf: fix redirect to map under tail calls 2018-08-17 15:56:23 -07:00
devmap.c bpf: fix redirect to map under tail calls 2018-08-17 15:56:23 -07:00
disasm.c bpf: Remove struct bpf_verifier_env argument from print_bpf_insn 2018-03-23 17:38:57 +01:00
disasm.h bpf: Remove struct bpf_verifier_env argument from print_bpf_insn 2018-03-23 17:38:57 +01:00
hashtab.c bpf: use per htab salt for bucket hash 2018-08-23 18:45:47 +02:00
helpers.c bpf: introduce the bpf_get_local_storage() helper function 2018-08-03 00:47:32 +02:00
inode.c bpf: decouple btf from seq bpf fs dump and enable more maps 2018-08-13 00:52:45 +02:00
local_storage.c bpf: allocate local storage buffers using GFP_ATOMIC 2018-12-17 09:24:33 +01:00
lpm_trie.c bpf: decouple btf from seq bpf fs dump and enable more maps 2018-08-13 00:52:45 +02:00
Makefile bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY 2018-08-11 01:58:46 +02:00
map_in_map.c bpf: fix inner map masking to prevent oob under speculation 2019-01-31 08:14:41 +01:00
map_in_map.h bpf: Add syscall lookup support for fd array and htab 2017-06-29 13:13:25 -04:00
offload.c bpf: offload: allow program and map sharing per-ASIC 2018-07-18 15:10:34 +02:00
percpu_freelist.c bpf: fix lockdep splat 2017-11-15 19:46:32 +09:00
percpu_freelist.h bpf: introduce percpu_freelist 2016-03-08 15:28:31 -05:00
reuseport_array.c bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY 2018-08-11 01:58:46 +02:00
sockmap.c bpf: sockmap, fix transition through disconnect without close 2018-09-22 02:46:41 +02:00
stackmap.c bpf: decouple btf from seq bpf fs dump and enable more maps 2018-08-13 00:52:45 +02:00
syscall.c bpf: fix bpf_prog_get_info_by_fd to return 0 func_lens for unpriv 2018-11-27 16:13:03 +01:00
tnum.c bpf/verifier: improve register value range tracking with ARSH 2018-04-29 08:45:53 -07:00
verifier.c bpf: fix sanitation of alu op with pointer / scalar type from different paths 2019-01-31 08:14:41 +01:00
xskmap.c xsk: do not call synchronize_net() under RCU read lock 2018-10-11 10:19:01 +02:00