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author | Alexei Starovoitov <ast@kernel.org> | 2024-02-22 08:54:47 -0800 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2024-03-05 16:15:57 -0800 |
commit | 399eca1bd4fc14645dcdf19ee10adf5cde85aecf (patch) | |
tree | 9679deaf78e877789d754ee7f82f9d1b874e64fa | |
parent | 685f7d531264599b3f167f1e94bbd22f120e5fab (diff) | |
parent | 5c2bc5e2f81d3344095ae241032dde20a4ea2b48 (diff) |
Merge branch 'check-bpf_func_state-callback_depth-when-pruning-states'
Eduard Zingerman says:
====================
check bpf_func_state->callback_depth when pruning states
This patch-set fixes bug in states pruning logic hit in mailing list
discussion [0]. The details of the fix are in patch #1.
The main idea for the fix belongs to Yonghong Song,
mine contribution is merely in review and test cases.
There are some changes in verification performance:
File Program Insns (DIFF) States (DIFF)
------------------------- ------------- --------------- --------------
pyperf600_bpf_loop.bpf.o on_event +15 (+0.42%) +0 (+0.00%)
strobemeta_bpf_loop.bpf.o on_event +857 (+37.95%) +60 (+38.96%)
xdp_synproxy_kern.bpf.o syncookie_tc +2892 (+30.39%) +109 (+36.33%)
xdp_synproxy_kern.bpf.o syncookie_xdp +2892 (+30.01%) +109 (+36.09%)
(when tested on a subset of selftests identified by
selftests/bpf/veristat.cfg and Cilium bpf object files from [4])
Changelog:
v2 [2] -> v3:
- fixes for verifier.c commit message as suggested by Yonghong;
- patch-set re-rerouted to 'bpf' tree as suggested in [2];
- patch for test_tcp_custom_syncookie is sent separately to 'bpf-next' [3].
- veristat results updated using 'bpf' tree as baseline and clang 16.
v1 [1] -> v2:
- patch #2 commit message updated to better reflect verifier behavior
with regards to checkpoints tree (suggested by Yonghong);
- veristat results added (suggested by Andrii).
[0] https://lore.kernel.org/bpf/9b251840-7cb8-4d17-bd23-1fc8071d8eef@linux.dev/
[1] https://lore.kernel.org/bpf/20240212143832.28838-1-eddyz87@gmail.com/
[2] https://lore.kernel.org/bpf/20240216150334.31937-1-eddyz87@gmail.com/
[3] https://lore.kernel.org/bpf/20240222150300.14909-1-eddyz87@gmail.com/
[4] https://github.com/anakryiko/cilium
====================
Link: https://lore.kernel.org/r/20240222154121.6991-1-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
-rw-r--r-- | kernel/bpf/verifier.c | 3 | ||||
-rw-r--r-- | tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c | 70 |
2 files changed, 73 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b263f093ee76..ddea9567f755 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -16602,6 +16602,9 @@ static bool func_states_equal(struct bpf_verifier_env *env, struct bpf_func_stat { int i; + if (old->callback_depth > cur->callback_depth) + return false; + for (i = 0; i < MAX_BPF_REG; i++) if (!regsafe(env, &old->regs[i], &cur->regs[i], &env->idmap_scratch, exact)) diff --git a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c index 5905e036e0ea..a955a6358206 100644 --- a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c +++ b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c @@ -239,4 +239,74 @@ int bpf_loop_iter_limit_nested(void *unused) return 1000 * a + b + c; } +struct iter_limit_bug_ctx { + __u64 a; + __u64 b; + __u64 c; +}; + +static __naked void iter_limit_bug_cb(void) +{ + /* This is the same as C code below, but written + * in assembly to control which branches are fall-through. + * + * switch (bpf_get_prandom_u32()) { + * case 1: ctx->a = 42; break; + * case 2: ctx->b = 42; break; + * default: ctx->c = 42; break; + * } + */ + asm volatile ( + "r9 = r2;" + "call %[bpf_get_prandom_u32];" + "r1 = r0;" + "r2 = 42;" + "r0 = 0;" + "if r1 == 0x1 goto 1f;" + "if r1 == 0x2 goto 2f;" + "*(u64 *)(r9 + 16) = r2;" + "exit;" + "1: *(u64 *)(r9 + 0) = r2;" + "exit;" + "2: *(u64 *)(r9 + 8) = r2;" + "exit;" + : + : __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +SEC("tc") +__failure +__flag(BPF_F_TEST_STATE_FREQ) +int iter_limit_bug(struct __sk_buff *skb) +{ + struct iter_limit_bug_ctx ctx = { 7, 7, 7 }; + + bpf_loop(2, iter_limit_bug_cb, &ctx, 0); + + /* This is the same as C code below, + * written in assembly to guarantee checks order. + * + * if (ctx.a == 42 && ctx.b == 42 && ctx.c == 7) + * asm volatile("r1 /= 0;":::"r1"); + */ + asm volatile ( + "r1 = *(u64 *)%[ctx_a];" + "if r1 != 42 goto 1f;" + "r1 = *(u64 *)%[ctx_b];" + "if r1 != 42 goto 1f;" + "r1 = *(u64 *)%[ctx_c];" + "if r1 != 7 goto 1f;" + "r1 /= 0;" + "1:" + : + : [ctx_a]"m"(ctx.a), + [ctx_b]"m"(ctx.b), + [ctx_c]"m"(ctx.c) + : "r1" + ); + return 0; +} + char _license[] SEC("license") = "GPL"; |