[PATCH V2 net 2/3] ARM: net: handle negative offsets in BPF JIT.
flat view
STALE4112d
From: Nicolas Schichan <hidden>
Date: 2015-07-21 12:14:32
Also in:
linux-arm-kernel, lkml
Subsystem:
arm port, bpf jit for arm, bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Russell King, Puranjay Mohan, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
Previously, the JIT would reject negative offsets known during code
generation and mishandle negative offsets provided at runtime.
Fix that by calling bpf_internal_load_pointer_neg_helper()
appropriately in the jit_get_skb_{b,h,w} slow path helpers and by forcing
the execution flow to the slow path helpers when the offset is
negative.
Signed-off-by: Nicolas Schichan <redacted>
---
arch/arm/net/bpf_jit_32.c | 47 ++++++++++++++++++++++++++++++++++++++---------
1 file changed, 38 insertions(+), 9 deletions(-)
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 21f5ace..d9b2524 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c@@ -74,32 +74,52 @@ struct jit_ctx { int bpf_jit_enable __read_mostly; -static u64 jit_get_skb_b(struct sk_buff *skb, unsigned offset) +static inline int call_neg_helper(struct sk_buff *skb, int offset, void *ret, + unsigned int size) +{ + void *ptr = bpf_internal_load_pointer_neg_helper(skb, offset, size); + + if (!ptr) + return -EFAULT; + memcpy(ret, ptr, size); + return 0; +} + +static u64 jit_get_skb_b(struct sk_buff *skb, int offset) { u8 ret; int err; - err = skb_copy_bits(skb, offset, &ret, 1); + if (offset < 0) + err = call_neg_helper(skb, offset, &ret, 1); + else + err = skb_copy_bits(skb, offset, &ret, 1); return (u64)err << 32 | ret; } -static u64 jit_get_skb_h(struct sk_buff *skb, unsigned offset) +static u64 jit_get_skb_h(struct sk_buff *skb, int offset) { u16 ret; int err; - err = skb_copy_bits(skb, offset, &ret, 2); + if (offset < 0) + err = call_neg_helper(skb, offset, &ret, 2); + else + err = skb_copy_bits(skb, offset, &ret, 2); return (u64)err << 32 | ntohs(ret); } -static u64 jit_get_skb_w(struct sk_buff *skb, unsigned offset) +static u64 jit_get_skb_w(struct sk_buff *skb, int offset) { u32 ret; int err; - err = skb_copy_bits(skb, offset, &ret, 4); + if (offset < 0) + err = call_neg_helper(skb, offset, &ret, 4); + else + err = skb_copy_bits(skb, offset, &ret, 4); return (u64)err << 32 | ntohl(ret); }
@@ -536,9 +556,6 @@ static int build_body(struct jit_ctx *ctx) case BPF_LD | BPF_B | BPF_ABS: load_order = 0; load: - /* the interpreter will deal with the negative K */ - if ((int)k < 0) - return -ENOTSUPP; emit_mov_i(r_off, k, ctx); load_common: ctx->seen |= SEEN_DATA | SEEN_CALL;
@@ -553,6 +570,18 @@ load_common: condt = ARM_COND_HI; } + /* + * test for negative offset, only if we are + * currently scheduled to take the fast + * path. this will update the flags so that + * the slowpath instruction are ignored if the + * offset is negative. + * + * for loard_order == 0 the HI condition will + * make loads at offset 0 take the slow path too. + */ + _emit(condt, ARM_CMP_I(r_off, 0), ctx); + _emit(condt, ARM_ADD_R(r_scratch, r_off, r_skb_data), ctx);
--
1.9.1