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

Daniel Borkmann says:

====================
pull-request: bpf 2020-01-07

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

We've added 2 non-merge commits during the last 1 day(s) which contain
a total of 2 files changed, 16 insertions(+), 4 deletions(-).

The main changes are:

1) Fix a use-after-free in cgroup BPF due to auto-detachment, from Roman Gushchin.

2) Fix skb out-of-bounds access in ld_abs/ind instruction, from Daniel Borkmann.
====================

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

kernel/bpf/cgroup.c

@@ -35,8 +35,8 @@ void cgroup_bpf_offline(struct cgroup *cgrp)
  */
 static void cgroup_bpf_release(struct work_struct *work)
 {
-	struct cgroup *cgrp = container_of(work, struct cgroup,
-					   bpf.release_work);
+	struct cgroup *p, *cgrp = container_of(work, struct cgroup,
+					       bpf.release_work);
 	enum bpf_cgroup_storage_type stype;
 	struct bpf_prog_array *old_array;
 	unsigned int type;
@@ -65,6 +65,9 @@ static void cgroup_bpf_release(struct work_struct *work)
 
 	mutex_unlock(&cgroup_mutex);
 
+	for (p = cgroup_parent(cgrp); p; p = cgroup_parent(p))
+		cgroup_bpf_put(p);
+
 	percpu_ref_exit(&cgrp->bpf.refcnt);
 	cgroup_put(cgrp);
 }
@@ -199,13 +202,17 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
  */
 #define	NR ARRAY_SIZE(cgrp->bpf.effective)
 	struct bpf_prog_array *arrays[NR] = {};
+	struct cgroup *p;
 	int ret, i;
 
 	ret = percpu_ref_init(&cgrp->bpf.refcnt, cgroup_bpf_release_fn, 0,
 			      GFP_KERNEL);
 	if (ret)
 		return ret;
 
+	for (p = cgroup_parent(cgrp); p; p = cgroup_parent(p))
+		cgroup_bpf_get(p);
+
 	for (i = 0; i < NR; i++)
 		INIT_LIST_HEAD(&cgrp->bpf.progs[i]);
 

kernel/bpf/verifier.c

@@ -6264,6 +6264,7 @@ static bool may_access_skb(enum bpf_prog_type type)
 static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 {
 	struct bpf_reg_state *regs = cur_regs(env);
+	static const int ctx_reg = BPF_REG_6;
 	u8 mode = BPF_MODE(insn->code);
 	int i, err;
 
@@ -6297,7 +6298,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	}
 
 	/* check whether implicit source operand (register R6) is readable */
-	err = check_reg_arg(env, BPF_REG_6, SRC_OP);
+	err = check_reg_arg(env, ctx_reg, SRC_OP);
 	if (err)
 		return err;
 
@@ -6316,7 +6317,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 		return -EINVAL;
 	}
 
-	if (regs[BPF_REG_6].type != PTR_TO_CTX) {
+	if (regs[ctx_reg].type != PTR_TO_CTX) {
 		verbose(env,
 			"at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
 		return -EINVAL;
@@ -6329,6 +6330,10 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 			return err;
 	}
 
+	err = check_ctx_reg(env, &regs[ctx_reg], ctx_reg);
+	if (err < 0)
+		return err;
+
 	/* reset caller saved regs to unreadable */
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		mark_reg_not_init(env, regs, caller_saved[i]);