Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Daniel Borkmann says:

====================
pull-request: bpf 2018-01-18

The following pull-request contains BPF updates for your *net* tree.

The main changes are:

1) Fix a divide by zero due to wrong if (src_reg == 0) check in
64-bit mode. Properly handle this in interpreter and mask it
also generically in verifier to guard against similar checks
in JITs, from Eric and Alexei.

2) Fix a bug in arm64 JIT when tail calls are involved and progs
have different stack sizes, from Daniel.

3) Reject stores into BPF context that are not expected BPF_STX |
BPF_MEM variant, from Daniel.

4) Mark dst reg as unknown on {s,u}bounds adjustments when the
src reg has derived bounds from dead branches, from Daniel.
====================

Signed-off-by: David S. Miller <[e-mail]>

arch/arm64/net/bpf_jit_comp.c

···
 /* Stack must be multiples of 16B */
 #define STACK_ALIGN(sz) (((sz) + 15) & ~15)
 
-#define PROLOGUE_OFFSET 8
+/* Tail call offset to jump into */
+#define PROLOGUE_OFFSET 7
 
 static int build_prologue(struct jit_ctx *ctx)
 {
···
 	/* Initialize tail_call_cnt */
 	emit(A64_MOVZ(1, tcc, 0, 0), ctx);
 
-	/* 4 byte extra for skb_copy_bits buffer */
-	ctx->stack_size = prog->aux->stack_depth + 4;
-	ctx->stack_size = STACK_ALIGN(ctx->stack_size);
-
-	/* Set up function call stack */
-	emit(A64_SUB_I(1, A64_SP, A64_SP, ctx->stack_size), ctx);
-
 	cur_offset = ctx->idx - idx0;
 	if (cur_offset != PROLOGUE_OFFSET) {
 		pr_err_once("PROLOGUE_OFFSET = %d, expected %d!\n",
 			    cur_offset, PROLOGUE_OFFSET);
 		return -1;
 	}
+
+	/* 4 byte extra for skb_copy_bits buffer */
+	ctx->stack_size = prog->aux->stack_depth + 4;
+	ctx->stack_size = STACK_ALIGN(ctx->stack_size);
+
+	/* Set up function call stack */
+	emit(A64_SUB_I(1, A64_SP, A64_SP, ctx->stack_size), ctx);
 	return 0;
 }
 
···
 	emit(A64_LDR64(prg, tmp, prg), ctx);
 	emit(A64_CBZ(1, prg, jmp_offset), ctx);
 
-	/* goto *(prog->bpf_func + prologue_size); */
+	/* goto *(prog->bpf_func + prologue_offset); */
 	off = offsetof(struct bpf_prog, bpf_func);
 	emit_a64_mov_i64(tmp, off, ctx);
 	emit(A64_LDR64(tmp, prg, tmp), ctx);
 	emit(A64_ADD_I(1, tmp, tmp, sizeof(u32) * PROLOGUE_OFFSET), ctx);
+	emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_size), ctx);
 	emit(A64_BR(tmp), ctx);
 
 	/* out: */

kernel/bpf/core.c

···
 		DST = tmp;
 		CONT;
 	ALU_MOD_X:
-		if (unlikely(SRC == 0))
+		if (unlikely((u32)SRC == 0))
 			return 0;
 		tmp = (u32) DST;
 		DST = do_div(tmp, (u32) SRC);
···
 		DST = div64_u64(DST, SRC);
 		CONT;
 	ALU_DIV_X:
-		if (unlikely(SRC == 0))
+		if (unlikely((u32)SRC == 0))
 			return 0;
 		tmp = (u32) DST;
 		do_div(tmp, (u32) SRC);

kernel/bpf/verifier.c

···
 	return __is_pointer_value(env->allow_ptr_leaks, cur_regs(env) + regno);
 }
 
+static bool is_ctx_reg(struct bpf_verifier_env *env, int regno)
+{
+	const struct bpf_reg_state *reg = cur_regs(env) + regno;
+
+	return reg->type == PTR_TO_CTX;
+}
+
 static int check_pkt_ptr_alignment(struct bpf_verifier_env *env,
 				   const struct bpf_reg_state *reg,
 				   int off, int size, bool strict)
···
 
 	if (is_pointer_value(env, insn->src_reg)) {
 		verbose(env, "R%d leaks addr into mem\n", insn->src_reg);
+		return -EACCES;
+	}
+
+	if (is_ctx_reg(env, insn->dst_reg)) {
+		verbose(env, "BPF_XADD stores into R%d context is not allowed\n",
+			insn->dst_reg);
 		return -EACCES;
 	}
 
···
 
 	dst_reg = &regs[dst];
 
-	if (WARN_ON_ONCE(known && (smin_val != smax_val))) {
-		print_verifier_state(env, env->cur_state);
-		verbose(env,
-			"verifier internal error: known but bad sbounds\n");
-		return -EINVAL;
-	}
-	if (WARN_ON_ONCE(known && (umin_val != umax_val))) {
-		print_verifier_state(env, env->cur_state);
-		verbose(env,
-			"verifier internal error: known but bad ubounds\n");
-		return -EINVAL;
+	if ((known && (smin_val != smax_val || umin_val != umax_val)) ||
+	    smin_val > smax_val || umin_val > umax_val) {
+		/* Taint dst register if offset had invalid bounds derived from
+		 * e.g. dead branches.
+		 */
+		__mark_reg_unknown(dst_reg);
+		return 0;
 	}
 
 	if (BPF_CLASS(insn->code) != BPF_ALU64) {
···
 	umax_val = src_reg.umax_value;
 	src_known = tnum_is_const(src_reg.var_off);
 	dst_known = tnum_is_const(dst_reg->var_off);
+
+	if ((src_known && (smin_val != smax_val || umin_val != umax_val)) ||
+	    smin_val > smax_val || umin_val > umax_val) {
+		/* Taint dst register if offset had invalid bounds derived from
+		 * e.g. dead branches.
+		 */
+		__mark_reg_unknown(dst_reg);
+		return 0;
+	}
 
 	if (!src_known &&
 	    opcode != BPF_ADD && opcode != BPF_SUB && opcode != BPF_AND) {
···
 			if (err)
 				return err;
 
+			if (is_ctx_reg(env, insn->dst_reg)) {
+				verbose(env, "BPF_ST stores into R%d context is not allowed\n",
+					insn->dst_reg);
+				return -EACCES;
+			}
+
 			/* check that memory (dst_reg + off) is writeable */
 			err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
 					       BPF_SIZE(insn->code), BPF_WRITE,
···
 	int i, cnt, delta = 0;
 
 	for (i = 0; i < insn_cnt; i++, insn++) {
+		if (insn->code == (BPF_ALU | BPF_MOD | BPF_X) ||
+		    insn->code == (BPF_ALU | BPF_DIV | BPF_X)) {
+			/* due to JIT bugs clear upper 32-bits of src register
+			 * before div/mod operation
+			 */
+			insn_buf[0] = BPF_MOV32_REG(insn->src_reg, insn->src_reg);
+			insn_buf[1] = *insn;
+			cnt = 2;
+			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
+			if (!new_prog)
+				return -ENOMEM;
+
+			delta    += cnt - 1;
+			env->prog = prog = new_prog;
+			insn      = new_prog->insnsi + i + delta;
+			continue;
+		}
+
 		if (insn->code != (BPF_JMP | BPF_CALL))
 			continue;
 

net/core/filter.c

···
 			    convert_bpf_extensions(fp, &insn))
 				break;
 
+			if (fp->code == (BPF_ALU | BPF_DIV | BPF_X) ||
+			    fp->code == (BPF_ALU | BPF_MOD | BPF_X))
+				*insn++ = BPF_MOV32_REG(BPF_REG_X, BPF_REG_X);
+
 			*insn = BPF_RAW_INSN(fp->code, BPF_REG_A, BPF_REG_X, 0, fp->k);
 			break;
 

tools/testing/selftests/bpf/test_verifier.c

···
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	},
 	{
+		"context stores via ST",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_ST_MEM(BPF_DW, BPF_REG_1, offsetof(struct __sk_buff, mark), 0),
+			BPF_EXIT_INSN(),
+		},
+		.errstr = "BPF_ST stores into R1 context is not allowed",
+		.result = REJECT,
+		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+	},
+	{
+		"context stores via XADD",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_W, BPF_REG_1,
+				     BPF_REG_0, offsetof(struct __sk_buff, mark), 0),
+			BPF_EXIT_INSN(),
+		},
+		.errstr = "BPF_XADD stores into R1 context is not allowed",
+		.result = REJECT,
+		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+	},
+	{
 		"direct packet access: test1",
 		.insns = {
 			BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1,
···
 		.fixup_map1 = { 2 },
 		.errstr_unpriv = "R2 leaks addr into mem",
 		.result_unpriv = REJECT,
-		.result = ACCEPT,
+		.result = REJECT,
+		.errstr = "BPF_XADD stores into R1 context is not allowed",
 	},
 	{
 		"leak pointer into ctx 2",
···
 		},
 		.errstr_unpriv = "R10 leaks addr into mem",
 		.result_unpriv = REJECT,
-		.result = ACCEPT,
+		.result = REJECT,
+		.errstr = "BPF_XADD stores into R1 context is not allowed",
 	},
 	{
 		"leak pointer into ctx 3",
···
 			BPF_JMP_IMM(BPF_JA, 0, 0, -7),
 		},
 		.fixup_map1 = { 4 },
-		.errstr = "unbounded min value",
+		.errstr = "R0 invalid mem access 'inv'",
 		.result = REJECT,
 	},
 	{
···
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_XDP,
 		.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
+	},
+	{
+		"check deducing bounds from const, 1",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 1, 0),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		},
+		.result = REJECT,
+		.errstr = "R0 tried to subtract pointer from scalar",
+	},
+	{
+		"check deducing bounds from const, 2",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 1, 1),
+			BPF_EXIT_INSN(),
+			BPF_JMP_IMM(BPF_JSLE, BPF_REG_0, 1, 1),
+			BPF_EXIT_INSN(),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_0),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+	},
+	{
+		"check deducing bounds from const, 3",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_IMM(BPF_JSLE, BPF_REG_0, 0, 0),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		},
+		.result = REJECT,
+		.errstr = "R0 tried to subtract pointer from scalar",
+	},
+	{
+		"check deducing bounds from const, 4",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_IMM(BPF_JSLE, BPF_REG_0, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_0),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+	},
+	{
+		"check deducing bounds from const, 5",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 1),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		},
+		.result = REJECT,
+		.errstr = "R0 tried to subtract pointer from scalar",
+	},
+	{
+		"check deducing bounds from const, 6",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		},
+		.result = REJECT,
+		.errstr = "R0 tried to subtract pointer from scalar",
+	},
+	{
+		"check deducing bounds from const, 7",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, ~0),
+			BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 0),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_0),
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+				    offsetof(struct __sk_buff, mark)),
+			BPF_EXIT_INSN(),
+		},
+		.result = REJECT,
+		.errstr = "dereference of modified ctx ptr",
+	},
+	{
+		"check deducing bounds from const, 8",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, ~0),
+			BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 1),
+			BPF_ALU64_REG(BPF_ADD, BPF_REG_1, BPF_REG_0),
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+				    offsetof(struct __sk_buff, mark)),
+			BPF_EXIT_INSN(),
+		},
+		.result = REJECT,
+		.errstr = "dereference of modified ctx ptr",
+	},
+	{
+		"check deducing bounds from const, 9",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 0),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		},
+		.result = REJECT,
+		.errstr = "R0 tried to subtract pointer from scalar",
+	},
+	{
+		"check deducing bounds from const, 10",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_IMM(BPF_JSLE, BPF_REG_0, 0, 0),
+			/* Marks reg as unknown. */
+			BPF_ALU64_IMM(BPF_NEG, BPF_REG_0, 0),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		},
+		.result = REJECT,
+		.errstr = "math between ctx pointer and register with unbounded min value is not allowed",
 	},
 	{
 		"bpf_exit with invalid return code. test1",