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

Daniel Borkmann says:

====================
pull-request: bpf 2018-06-08

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

The main changes are:

1) Fix in the BPF verifier to reject modified ctx pointers on helper
   functions, from Daniel.

2) Fix in BPF kselftests for get_cgroup_id_user() helper to only
   record the cgroup id for a provided pid in order to reduce test
   failures from processes interferring with the test, from Yonghong.

3) Fix a crash in AF_XDP's mem accounting when the process owning
   the sock has CAP_IPC_LOCK capabilities set, from Daniel.

4) Fix an issue for AF_XDP on 32 bit machines where XDP_UMEM_PGOFF_*_RING
   defines need ULL suffixes and use loff_t type as they are otherwise
   truncated, from Geert.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 17 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d6403b5166f4..cced0c1e63e2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1617,6 +1617,30 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 }
 #endif
 
+static int check_ctx_reg(struct bpf_verifier_env *env,
+			 const struct bpf_reg_state *reg, int regno)
+{
+	/* Access to ctx or passing it to a helper is only allowed in
+	 * its original, unmodified form.
+	 */
+
+	if (reg->off) {
+		verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n",
+			regno, reg->off);
+		return -EACCES;
+	}
+
+	if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
+		char tn_buf[48];
+
+		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
+		verbose(env, "variable ctx access var_off=%s disallowed\n", tn_buf);
+		return -EACCES;
+	}
+
+	return 0;
+}
+
 /* truncate register to smaller size (in bytes)
  * must be called with size < BPF_REG_SIZE
  */
@@ -1686,24 +1710,11 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 			verbose(env, "R%d leaks addr into ctx\n", value_regno);
 			return -EACCES;
 		}
-		/* ctx accesses must be at a fixed offset, so that we can
-		 * determine what type of data were returned.
-		 */
-		if (reg->off) {
-			verbose(env,
-				"dereference of modified ctx ptr R%d off=%d+%d, ctx+const is allowed, ctx+const+const is not\n",
-				regno, reg->off, off - reg->off);
-			return -EACCES;
-		}
-		if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
-			char tn_buf[48];
 
-			tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
-			verbose(env,
-				"variable ctx access var_off=%s off=%d size=%d",
-				tn_buf, off, size);
-			return -EACCES;
-		}
+		err = check_ctx_reg(env, reg, regno);
+		if (err < 0)
+			return err;
+
 		err = check_ctx_access(env, insn_idx, off, size, t, &reg_type);
 		if (!err && t == BPF_READ && value_regno >= 0) {
 			/* ctx access returns either a scalar, or a
@@ -1984,6 +1995,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 		expected_type = PTR_TO_CTX;
 		if (type != expected_type)
 			goto err_type;
+		err = check_ctx_reg(env, reg, regno);
+		if (err < 0)
+			return err;
 	} else if (arg_type_is_mem_ptr(arg_type)) {
 		expected_type = PTR_TO_STACK;
 		/* One exception here. In case function allows for NULL to be