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authorAlexei Starovoitov <ast@kernel.org>2018-12-03 22:46:06 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-12-04 17:22:02 +0100
commitceefbc96fa5c5b975d87bf8e89ba8416f6b764d9 (patch)
tree46ba4c3e98ffb4eb565dfce9b0bb2fda5ef35ead /kernel
parent4f7b3e82589e0de723780198ec7983e427144c0a (diff)
downloadlinux-ceefbc96fa5c5b975d87bf8e89ba8416f6b764d9.tar.bz2
bpf: add per-insn complexity limit
malicious bpf program may try to force the verifier to remember a lot of distinct verifier states. Put a limit to number of per-insn 'struct bpf_verifier_state'. Note that hitting the limit doesn't reject the program. It potentially makes the verifier do more steps to analyze the program. It means that malicious programs will hit BPF_COMPLEXITY_LIMIT_INSNS sooner instead of spending cpu time walking long link list. The limit of BPF_COMPLEXITY_LIMIT_STATES==64 affects cilium progs with slight increase in number of "steps" it takes to successfully verify the programs: before after bpf_lb-DLB_L3.o 1940 1940 bpf_lb-DLB_L4.o 3089 3089 bpf_lb-DUNKNOWN.o 1065 1065 bpf_lxc-DDROP_ALL.o 28052 | 28162 bpf_lxc-DUNKNOWN.o 35487 | 35541 bpf_netdev.o 10864 10864 bpf_overlay.o 6643 6643 bpf_lcx_jit.o 38437 38437 But it also makes malicious program to be rejected in 0.4 seconds vs 6.5 Hence apply this limit to unprivileged programs only. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Edward Cree <ecree@solarflare.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 55a49703f423..fc760d00a38c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -175,6 +175,7 @@ struct bpf_verifier_stack_elem {
#define BPF_COMPLEXITY_LIMIT_INSNS 131072
#define BPF_COMPLEXITY_LIMIT_STACK 1024
+#define BPF_COMPLEXITY_LIMIT_STATES 64
#define BPF_MAP_PTR_UNPRIV 1UL
#define BPF_MAP_PTR_POISON ((void *)((0xeB9FUL << 1) + \
@@ -5047,7 +5048,7 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
struct bpf_verifier_state_list *new_sl;
struct bpf_verifier_state_list *sl;
struct bpf_verifier_state *cur = env->cur_state, *new;
- int i, j, err;
+ int i, j, err, states_cnt = 0;
sl = env->explored_states[insn_idx];
if (!sl)
@@ -5074,8 +5075,12 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
return 1;
}
sl = sl->next;
+ states_cnt++;
}
+ if (!env->allow_ptr_leaks && states_cnt > BPF_COMPLEXITY_LIMIT_STATES)
+ return 0;
+
/* there were no equivalent states, remember current one.
* technically the current state is not proven to be safe yet,
* but it will either reach outer most bpf_exit (which means it's safe)