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authorDaniel Borkmann <daniel@iogearbox.net>2019-04-03 18:39:14 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-20 09:15:09 +0200
commit0ed998d17cd421da18334745af7aee246abe4c70 (patch)
tree3cfb14dd6da877e4818777cbd302ecaf8ae80375
parent6588a490bfe1b879f11b5e74724ef53a33b68641 (diff)
bpf: fix inner map masking to prevent oob under speculation
commit 9d5564ddcf2a0f5ba3fa1c3a1f8a1b59ad309553 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: b2157399cc98 ("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: Vallish Vaidyeshwara <vallish@amazon.com> Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/bpf/map_in_map.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 1da574612bea..c0c494b7647b 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -12,6 +12,7 @@
struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
{
struct bpf_map *inner_map, *inner_map_meta;
+ u32 inner_map_meta_size;
struct fd f;
f = fdget(inner_map_ufd);
@@ -34,7 +35,12 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
return ERR_PTR(-EINVAL);
}
- inner_map_meta = kzalloc(sizeof(*inner_map_meta), GFP_USER);
+ inner_map_meta_size = sizeof(*inner_map_meta);
+ /* In some cases verifier needs to access beyond just base map. */
+ if (inner_map->ops == &array_map_ops)
+ inner_map_meta_size = sizeof(struct bpf_array);
+
+ inner_map_meta = kzalloc(inner_map_meta_size, GFP_USER);
if (!inner_map_meta) {
fdput(f);
return ERR_PTR(-ENOMEM);
@@ -44,9 +50,16 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
inner_map_meta->key_size = inner_map->key_size;
inner_map_meta->value_size = inner_map->value_size;
inner_map_meta->map_flags = inner_map->map_flags;
- inner_map_meta->ops = inner_map->ops;
inner_map_meta->max_entries = inner_map->max_entries;
+ /* Misc members not needed in bpf_map_meta_equal() check. */
+ inner_map_meta->ops = inner_map->ops;
+ if (inner_map->ops == &array_map_ops) {
+ inner_map_meta->unpriv_array = inner_map->unpriv_array;
+ container_of(inner_map_meta, struct bpf_array, map)->index_mask =
+ container_of(inner_map, struct bpf_array, map)->index_mask;
+ }
+
fdput(f);
return inner_map_meta;
}