From f4b16fce7a5a1ec8069b1f577476bdc1d2688cd1 Mon Sep 17 00:00:00 2001 From: Zi Shen Lim Date: Wed, 18 Nov 2015 00:56:02 -0800 Subject: [PATCH] arm64: bpf: fix buffer pointer During code review, I noticed we were passing a bad buffer pointer to bpf_load_pointer helper function called by jitted code. Point to the buffer allocated by JIT, so we don't silently corrupt other parts of the stack. Signed-off-by: Zi Shen Lim Acked-by: Yang Shi Signed-off-by: David S. Miller --- arch/arm64/net/bpf_jit_comp.c | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index d6a53ef2350b..7cf032bebf8c 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -139,6 +139,12 @@ static inline int epilogue_offset(const struct jit_ctx *ctx) /* Stack must be multiples of 16B */ #define STACK_ALIGN(sz) (((sz) + 15) & ~15) +#define _STACK_SIZE \ + (MAX_BPF_STACK \ + + 4 /* extra for skb_copy_bits buffer */) + +#define STACK_SIZE STACK_ALIGN(_STACK_SIZE) + static void build_prologue(struct jit_ctx *ctx) { const u8 r6 = bpf2a64[BPF_REG_6]; @@ -150,10 +156,6 @@ static void build_prologue(struct jit_ctx *ctx) const u8 rx = bpf2a64[BPF_REG_X]; const u8 tmp1 = bpf2a64[TMP_REG_1]; const u8 tmp2 = bpf2a64[TMP_REG_2]; - int stack_size = MAX_BPF_STACK; - - stack_size += 4; /* extra for skb_copy_bits buffer */ - stack_size = STACK_ALIGN(stack_size); /* * BPF prog stack layout @@ -165,12 +167,13 @@ static void build_prologue(struct jit_ctx *ctx) * | ... | callee saved registers * +-----+ * | | x25/x26 - * BPF fp register => -80:+-----+ + * BPF fp register => -80:+-----+ <= (BPF_FP) * | | * | ... | BPF prog stack * | | - * | | - * current A64_SP => +-----+ + * +-----+ <= (BPF_FP - MAX_BPF_STACK) + * |RSVD | JIT scratchpad + * current A64_SP => +-----+ <= (BPF_FP - STACK_SIZE) * | | * | ... | Function call stack * | | @@ -196,7 +199,7 @@ static void build_prologue(struct jit_ctx *ctx) emit(A64_MOV(1, fp, A64_SP), ctx); /* Set up function call stack */ - emit(A64_SUB_I(1, A64_SP, A64_SP, stack_size), ctx); + emit(A64_SUB_I(1, A64_SP, A64_SP, STACK_SIZE), ctx); /* Clear registers A and X */ emit_a64_mov_i64(ra, 0, ctx); @@ -213,13 +216,9 @@ static void build_epilogue(struct jit_ctx *ctx) const u8 fp = bpf2a64[BPF_REG_FP]; const u8 tmp1 = bpf2a64[TMP_REG_1]; const u8 tmp2 = bpf2a64[TMP_REG_2]; - int stack_size = MAX_BPF_STACK; - - stack_size += 4; /* extra for skb_copy_bits buffer */ - stack_size = STACK_ALIGN(stack_size); /* We're done with BPF stack */ - emit(A64_ADD_I(1, A64_SP, A64_SP, stack_size), ctx); + emit(A64_ADD_I(1, A64_SP, A64_SP, STACK_SIZE), ctx); /* Restore fs (x25) and x26 */ emit(A64_POP(fp, A64_R(26), A64_SP), ctx); @@ -658,7 +657,7 @@ emit_cond_jmp: return -EINVAL; } emit_a64_mov_i64(r3, size, ctx); - emit(A64_ADD_I(1, r4, fp, MAX_BPF_STACK), ctx); + emit(A64_SUB_I(1, r4, fp, STACK_SIZE), ctx); emit_a64_mov_i64(r5, (unsigned long)bpf_load_pointer, ctx); emit(A64_PUSH(A64_FP, A64_LR, A64_SP), ctx); emit(A64_MOV(1, A64_FP, A64_SP), ctx); -- 2.20.1