From: Aichun Li liaichun@huawei.com
mainline inclusion from mainline-v5.11-rc5 commit c04c0d2b968ac45d6ef020316808ef6c82325a82 category: bugfix bugzilla: 47241 CVE: NA
-------------------
Large verifier speed improvements allow to increase verifier complexity limit. Now regardless of the program composition and its size it takes little time for the verifier to hit insn_processed limit. On typical x86 machine non-debug kernel processes 1M instructions in 1/10 of a second. (before these speed improvements specially crafted programs could be hitting multi-second verification times) Full kasan kernel with debug takes ~1 second for the same 1M insns. Hence bump the BPF_COMPLEXITY_LIMIT_INSNS limit to 1M. Also increase the number of instructions per program from 4k to internal BPF_COMPLEXITY_LIMIT_INSNS limit. 4k limit was confusing to users, since small programs with hundreds of insns could be hitting BPF_COMPLEXITY_LIMIT_INSNS limit. Sometimes adding more insns and bpf_trace_printk debug statements would make the verifier accept the program while removing code would make the verifier reject it. Some user space application started to add #define MAX_FOO to their programs and do: MAX_FOO=100; again: compile with MAX_FOO; try to load; if (fails_to_load) { reduce MAX_FOO; goto again; } to be able to fit maximum amount of processing into single program. Other users artificially split their single program into a set of programs and use all 32 iterations of tail_calls to increase compute limits. And the most advanced folks used unlimited tc-bpf filter list to execute many bpf programs. Essentially the users managed to workaround 4k insn limit. This patch removes the limit for root programs from uapi. BPF_COMPLEXITY_LIMIT_INSNS is the kernel internal limit and success to load the program no longer depends on program size, but on 'smartness' of the verifier only. The verifier will continue to get smarter with every kernel release.
Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net
Signed-off-by: Aichun Li liaichun@huawei.com Reviewed-by: Yue Haibing yuehaibing@huawei.com Reviewed-by: Di Zhu zhudi21@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- include/linux/bpf.h | 1 + kernel/bpf/syscall.c | 3 ++- kernel/bpf/verifier.c | 1 - 3 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 0cc25af3457ff..432c4cf2a418d 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -328,6 +328,7 @@ struct bpf_array { }; };
+#define BPF_COMPLEXITY_LIMIT_INSNS 1000000 /* yes. 1M insns */ #define MAX_TAIL_CALL_CNT 32
struct bpf_event_entry { diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 80bffe7943f9d..fc0628d133166 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1399,7 +1399,8 @@ static int bpf_prog_load(union bpf_attr *attr) /* eBPF programs must be GPL compatible to use GPL-ed functions */ is_gpl = license_is_gpl_compatible(license);
- if (attr->insn_cnt == 0 || attr->insn_cnt > BPF_MAXINSNS) + if (attr->insn_cnt == 0 || + attr->insn_cnt > (capable(CAP_SYS_ADMIN) ? BPF_COMPLEXITY_LIMIT_INSNS : BPF_MAXINSNS)) return -E2BIG;
if (type == BPF_PROG_TYPE_KPROBE && diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 91b6e91a9765d..f6b7920917f92 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -154,7 +154,6 @@ struct bpf_verifier_stack_elem { struct bpf_verifier_stack_elem *next; };
-#define BPF_COMPLEXITY_LIMIT_INSNS 131072 #define BPF_COMPLEXITY_LIMIT_STACK 1024 #define BPF_COMPLEXITY_LIMIT_STATES 64