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Message-Id: <1453672883-2708-124-git-send-email-luis.henriques@canonical.com>
Date: Sun, 24 Jan 2016 22:01:18 +0000
From: Luis Henriques <luis.henriques@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Rabin Vincent <rabin@....in>,
"David S . Miller" <davem@...emloft.net>,
Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 123/128] net: filter: make JITs zero A for SKF_AD_ALU_XOR_X
3.16.7-ckt23 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Rabin Vincent <rabin@....in>
commit 55795ef5469290f89f04e12e662ded604909e462 upstream.
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 <rabin@....in>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
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(-)
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 75ee31c95ff3..4a7fe29635ea 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -161,23 +161,9 @@ static inline int mem_words_used(struct jit_ctx *ctx)
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 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
@@ -207,7 +193,7 @@ static void build_prologue(struct jit_ctx *ctx)
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 */
diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 965f1c116cc5..32751a0bba58 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -566,19 +566,6 @@ static inline u16 align_sp(unsigned int num)
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;
@@ -703,7 +690,6 @@ static unsigned int get_stack_depth(struct jit_ctx *ctx)
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 */
@@ -717,7 +703,7 @@ static void build_prologue(struct jit_ctx *ctx)
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);
}
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 82e82cadcde5..6a1c7ecfdd2c 100644
--- 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(struct sk_filter *fp, u32 *image,
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)
diff --git a/arch/sparc/net/bpf_jit_comp.c b/arch/sparc/net/bpf_jit_comp.c
index 8d4152f94c5a..ae966f86dcec 100644
--- 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 sk_filter *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;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index a7e3c48d73a7..02f857260bcb 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -373,6 +373,25 @@ void bpf_int_jit_compile(struct sk_filter *fp);
#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);
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