From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965905AbcA0TNu (ORCPT ); Wed, 27 Jan 2016 14:13:50 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:55095 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965722AbcA0TH3 (ORCPT ); Wed, 27 Jan 2016 14:07:29 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Rabin Vincent , Daniel Borkmann , Alexei Starovoitov , "David S. Miller" Subject: [PATCH 4.1 070/127] net: filter: make JITs zero A for SKF_AD_ALU_XOR_X Date: Wed, 27 Jan 2016 10:13:54 -0800 Message-Id: <20160127180809.156946534@linuxfoundation.org> X-Mailer: git-send-email 2.7.0 In-Reply-To: <20160127180805.624425994@linuxfoundation.org> References: <20160127180805.624425994@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Rabin Vincent [ Upstream commit 55795ef5469290f89f04e12e662ded604909e462 ] The SKF_AD_ALU_XOR_X ancillary is not like the other ancillary data instructions since it XORs A with X while all the others replace A with some loaded value. All the BPF JITs fail to clear A if this is used as the first instruction in a filter. This was found using american fuzzy lop. Add a helper to determine if A needs to be cleared given the first instruction in a filter, and use this in the JITs. Except for ARM, the rest have only been compile-tested. Fixes: 3480593131e0 ("net: filter: get rid of BPF_S_* enum") Signed-off-by: Rabin Vincent Acked-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- arch/arm/net/bpf_jit_32.c | 16 +--------------- arch/mips/net/bpf_jit.c | 16 +--------------- arch/powerpc/net/bpf_jit_comp.c | 13 ++----------- arch/sparc/net/bpf_jit_comp.c | 17 ++--------------- include/linux/filter.h | 19 +++++++++++++++++++ 5 files changed, 25 insertions(+), 56 deletions(-) --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -162,19 +162,6 @@ static inline int mem_words_used(struct return fls(ctx->seen & SEEN_MEM); } -static inline bool is_load_to_a(u16 inst) -{ - switch (inst) { - case BPF_LD | BPF_W | BPF_LEN: - case BPF_LD | BPF_W | BPF_ABS: - case BPF_LD | BPF_H | BPF_ABS: - case BPF_LD | BPF_B | BPF_ABS: - return true; - default: - return false; - } -} - static void jit_fill_hole(void *area, unsigned int size) { u32 *ptr; @@ -186,7 +173,6 @@ static void jit_fill_hole(void *area, un static void build_prologue(struct jit_ctx *ctx) { u16 reg_set = saved_regs(ctx); - u16 first_inst = ctx->skf->insns[0].code; u16 off; #ifdef CONFIG_FRAME_POINTER @@ -216,7 +202,7 @@ static void build_prologue(struct jit_ct emit(ARM_MOV_I(r_X, 0), ctx); /* do not leak kernel data to userspace */ - if ((first_inst != (BPF_RET | BPF_K)) && !(is_load_to_a(first_inst))) + if (bpf_needs_clear_a(&ctx->skf->insns[0])) emit(ARM_MOV_I(r_A, 0), ctx); /* stack space for the BPF_MEM words */ --- a/arch/mips/net/bpf_jit.c +++ b/arch/mips/net/bpf_jit.c @@ -556,19 +556,6 @@ static inline u16 align_sp(unsigned int return num; } -static bool is_load_to_a(u16 inst) -{ - switch (inst) { - case BPF_LD | BPF_W | BPF_LEN: - case BPF_LD | BPF_W | BPF_ABS: - case BPF_LD | BPF_H | BPF_ABS: - case BPF_LD | BPF_B | BPF_ABS: - return true; - default: - return false; - } -} - static void save_bpf_jit_regs(struct jit_ctx *ctx, unsigned offset) { int i = 0, real_off = 0; @@ -686,7 +673,6 @@ static unsigned int get_stack_depth(stru static void build_prologue(struct jit_ctx *ctx) { - u16 first_inst = ctx->skf->insns[0].code; int sp_off; /* Calculate the total offset for the stack pointer */ @@ -700,7 +686,7 @@ static void build_prologue(struct jit_ct emit_jit_reg_move(r_X, r_zero, ctx); /* Do not leak kernel data to userspace */ - if ((first_inst != (BPF_RET | BPF_K)) && !(is_load_to_a(first_inst))) + if (bpf_needs_clear_a(&ctx->skf->insns[0])) emit_jit_reg_move(r_A, r_zero, ctx); } --- a/arch/powerpc/net/bpf_jit_comp.c +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -78,18 +78,9 @@ static void bpf_jit_build_prologue(struc PPC_LI(r_X, 0); } - switch (filter[0].code) { - case BPF_RET | BPF_K: - case BPF_LD | BPF_W | BPF_LEN: - case BPF_LD | BPF_W | BPF_ABS: - case BPF_LD | BPF_H | BPF_ABS: - case BPF_LD | BPF_B | BPF_ABS: - /* first instruction sets A register (or is RET 'constant') */ - break; - default: - /* make sure we dont leak kernel information to user */ + /* make sure we dont leak kernel information to user */ + if (bpf_needs_clear_a(&filter[0])) PPC_LI(r_A, 0); - } } static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) --- a/arch/sparc/net/bpf_jit_comp.c +++ b/arch/sparc/net/bpf_jit_comp.c @@ -420,22 +420,9 @@ void bpf_jit_compile(struct bpf_prog *fp } emit_reg_move(O7, r_saved_O7); - switch (filter[0].code) { - case BPF_RET | BPF_K: - case BPF_LD | BPF_W | BPF_LEN: - case BPF_LD | BPF_W | BPF_ABS: - case BPF_LD | BPF_H | BPF_ABS: - case BPF_LD | BPF_B | BPF_ABS: - /* The first instruction sets the A register (or is - * a "RET 'constant'") - */ - break; - default: - /* Make sure we dont leak kernel information to the - * user. - */ + /* Make sure we dont leak kernel information to the user. */ + if (bpf_needs_clear_a(&filter[0])) emit_clear(r_A); /* A = 0 */ - } for (i = 0; i < flen; i++) { unsigned int K = filter[i].k; --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -428,6 +428,25 @@ static inline void bpf_jit_free(struct b #define BPF_ANC BIT(15) +static inline bool bpf_needs_clear_a(const struct sock_filter *first) +{ + switch (first->code) { + case BPF_RET | BPF_K: + case BPF_LD | BPF_W | BPF_LEN: + return false; + + case BPF_LD | BPF_W | BPF_ABS: + case BPF_LD | BPF_H | BPF_ABS: + case BPF_LD | BPF_B | BPF_ABS: + if (first->k == SKF_AD_OFF + SKF_AD_ALU_XOR_X) + return true; + return false; + + default: + return true; + } +} + static inline u16 bpf_anc_helper(const struct sock_filter *ftest) { BUG_ON(ftest->code & BPF_ANC);