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authorDaniel Borkmann <daniel@iogearbox.net>2017-06-29 03:04:59 +0200
committerDavid S. Miller <davem@davemloft.net>2017-06-29 15:44:34 -0400
commit6bdf6abc56b53103324dfd270a86580306e1a232 (patch)
tree2ab300507010ec4dc0895936ae04718984823086 /tools/testing
parentMerge branch 'arcnet-fixes' (diff)
downloadwireguard-linux-6bdf6abc56b53103324dfd270a86580306e1a232.tar.xz
wireguard-linux-6bdf6abc56b53103324dfd270a86580306e1a232.zip
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: 1be7f75d1668 ("bpf: enable non-root eBPF programs") Fixes: 17a5267067f3 ("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>
Diffstat (limited to 'tools/testing')
-rw-r--r--tools/testing/selftests/bpf/test_verifier.c66
1 files changed, 66 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index cabb19b1e371..0ff8c55c0464 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -3749,6 +3749,72 @@ static struct bpf_test tests[] = {
.errstr = "invalid bpf_context access",
},
{
+ "leak pointer into ctx 1",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0,
+ offsetof(struct __sk_buff, cb[0])),
+ BPF_LD_MAP_FD(BPF_REG_2, 0),
+ BPF_STX_XADD(BPF_DW, BPF_REG_1, BPF_REG_2,
+ offsetof(struct __sk_buff, cb[0])),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map1 = { 2 },
+ .errstr_unpriv = "R2 leaks addr into mem",
+ .result_unpriv = REJECT,
+ .result = ACCEPT,
+ },
+ {
+ "leak pointer into ctx 2",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0,
+ offsetof(struct __sk_buff, cb[0])),
+ BPF_STX_XADD(BPF_DW, BPF_REG_1, BPF_REG_10,
+ offsetof(struct __sk_buff, cb[0])),
+ BPF_EXIT_INSN(),
+ },
+ .errstr_unpriv = "R10 leaks addr into mem",
+ .result_unpriv = REJECT,
+ .result = ACCEPT,
+ },
+ {
+ "leak pointer into ctx 3",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_LD_MAP_FD(BPF_REG_2, 0),
+ BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_2,
+ offsetof(struct __sk_buff, cb[0])),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map1 = { 1 },
+ .errstr_unpriv = "R2 leaks addr into ctx",
+ .result_unpriv = REJECT,
+ .result = ACCEPT,
+ },
+ {
+ "leak pointer into map val",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+ BPF_FUNC_map_lookup_elem),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3),
+ BPF_MOV64_IMM(BPF_REG_3, 0),
+ BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_3, 0),
+ BPF_STX_XADD(BPF_DW, BPF_REG_0, BPF_REG_6, 0),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map1 = { 4 },
+ .errstr_unpriv = "R6 leaks addr into mem",
+ .result_unpriv = REJECT,
+ .result = ACCEPT,
+ },
+ {
"helper access to map: full range",
.insns = {
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),