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| author |   Eduard Zingerman <eddyz87@gmail.com> | 2022-06-24 05:06:13 +0300 |
|---|---|---|
| committer |   Daniel Borkmann <daniel@iogearbox.net> | 2022-06-24 16:51:00 +0200 |
| commit | 41188e9e9defa1678abbf860ad7f6dd1ba48ad1c (patch) | |
| tree | 5dce891137cb76dba82aeaae93a6d3d990e6f75a | |
| parent | bpf: Fix for use-after-free bug in inline_bpf_loop (diff) | |
| download | wireguard-linux-41188e9e9defa1678abbf860ad7f6dd1ba48ad1c.tar.xz wireguard-linux-41188e9e9defa1678abbf860ad7f6dd1ba48ad1c.zip | |
selftest/bpf: Test for use-after-free bug fix in inline_bpf_loop
This test verifies that bpf_loop() inlining works as expected when
address of `env->prog` is updated. This address is updated upon BPF
program reallocation.
Reallocation is handled by bpf_prog_realloc(), which reuses old memory
if page boundary is not crossed. The value of `len` in the test is
chosen to cross this boundary on bpf_loop() patching.
Verify that the use-after-free bug in inline_bpf_loop() reported by
Dan Carpenter is fixed.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220624020613.548108-3-eddyz87@gmail.com
| -rw-r--r-- | tools/testing/selftests/bpf/test_verifier.c | 39 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/verifier/bpf_loop_inline.c | 11 |
2 files changed, 50 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 7fe897c66d81..f9d553fbf68a 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -425,6 +425,45 @@ static void bpf_fill_torturous_jumps(struct bpf_test *self) } } +static void bpf_fill_big_prog_with_loop_1(struct bpf_test *self) +{ + struct bpf_insn *insn = self->fill_insns; + /* This test was added to catch a specific use after free + * error, which happened upon BPF program reallocation. + * Reallocation is handled by core.c:bpf_prog_realloc, which + * reuses old memory if page boundary is not crossed. The + * value of `len` is chosen to cross this boundary on bpf_loop + * patching. + */ + const int len = getpagesize() - 25; + int callback_load_idx; + int callback_idx; + int i = 0; + + insn[i++] = BPF_ALU64_IMM(BPF_MOV, BPF_REG_1, 1); + callback_load_idx = i; + insn[i++] = BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, + BPF_REG_2, BPF_PSEUDO_FUNC, 0, + 777 /* filled below */); + insn[i++] = BPF_RAW_INSN(0, 0, 0, 0, 0); + insn[i++] = BPF_ALU64_IMM(BPF_MOV, BPF_REG_3, 0); + insn[i++] = BPF_ALU64_IMM(BPF_MOV, BPF_REG_4, 0); + insn[i++] = BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_loop); + + while (i < len - 3) + insn[i++] = BPF_ALU64_IMM(BPF_MOV, BPF_REG_0, 0); + insn[i++] = BPF_EXIT_INSN(); + + callback_idx = i; + insn[i++] = BPF_ALU64_IMM(BPF_MOV, BPF_REG_0, 0); + insn[i++] = BPF_EXIT_INSN(); + + insn[callback_load_idx].imm = callback_idx - callback_load_idx - 1; + self->func_info[1].insn_off = callback_idx; + self->prog_len = i; + assert(i == len); +} + /* BPF_SK_LOOKUP contains 13 instructions, if you need to fix up maps */ #define BPF_SK_LOOKUP(func) \ /* struct bpf_sock_tuple tuple = {} */ \ diff --git a/tools/testing/selftests/bpf/verifier/bpf_loop_inline.c b/tools/testing/selftests/bpf/verifier/bpf_loop_inline.c index 232da07c93b5..2d0023659d88 100644 --- a/tools/testing/selftests/bpf/verifier/bpf_loop_inline.c +++ b/tools/testing/selftests/bpf/verifier/bpf_loop_inline.c @@ -244,6 +244,17 @@ .func_info_cnt = 3, BTF_TYPES }, +{ + "inline bpf_loop call in a big program", + .insns = {}, + .fill_helper = bpf_fill_big_prog_with_loop_1, + .expected_insns = { PSEUDO_CALL_INSN() }, + .unexpected_insns = { HELPER_CALL_INSN() }, + .result = ACCEPT, + .func_info = { { 0, MAIN_TYPE }, { 16, CALLBACK_TYPE } }, + .func_info_cnt = 2, + BTF_TYPES +}, #undef HELPER_CALL_INSN #undef PSEUDO_CALL_INSN |