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

Daniel Borkmann says:

====================
pull-request: bpf 2021-08-19

We've added 3 non-merge commits during the last 3 day(s) which contain
a total of 3 files changed, 29 insertions(+), 6 deletions(-).

The main changes are:

1) Fix to clear zext_dst for dead instructions which was causing invalid program
   rejections on JITs with bpf_jit_needs_zext such as s390x, from Ilya Leoshkevich.

2) Fix RCU splat in bpf_get_current_{ancestor_,}cgroup_id() helpers when they are
   invoked from sleepable programs, from Yonghong Song.

* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
  selftests, bpf: Test that dead ldx_w insns are accepted
  bpf: Clear zext_dst of dead insns
  bpf: Add rcu_read_lock in bpf_get_current_[ancestor_]cgroup_id() helpers
====================

Link: https://lore.kernel.org/r/20210819144904.20069-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

kernel/bpf/helpers.c

@@ -353,9 +353,15 @@ const struct bpf_func_proto bpf_jiffies64_proto = {
 #ifdef CONFIG_CGROUPS
 BPF_CALL_0(bpf_get_current_cgroup_id)
 {
-	struct cgroup *cgrp = task_dfl_cgroup(current);
+	struct cgroup *cgrp;
+	u64 cgrp_id;
 
-	return cgroup_id(cgrp);
+	rcu_read_lock();
+	cgrp = task_dfl_cgroup(current);
+	cgrp_id = cgroup_id(cgrp);
+	rcu_read_unlock();
+
+	return cgrp_id;
 }
 
 const struct bpf_func_proto bpf_get_current_cgroup_id_proto = {
@@ -366,13 +372,17 @@ const struct bpf_func_proto bpf_get_current_cgroup_id_proto = {
 
 BPF_CALL_1(bpf_get_current_ancestor_cgroup_id, int, ancestor_level)
 {
-	struct cgroup *cgrp = task_dfl_cgroup(current);
+	struct cgroup *cgrp;
 	struct cgroup *ancestor;
+	u64 cgrp_id;
 
+	rcu_read_lock();
+	cgrp = task_dfl_cgroup(current);
 	ancestor = cgroup_ancestor(cgrp, ancestor_level);
-	if (!ancestor)
-		return 0;
-	return cgroup_id(ancestor);
+	cgrp_id = ancestor ? cgroup_id(ancestor) : 0;
+	rcu_read_unlock();
+
+	return cgrp_id;
 }
 
 const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto = {

kernel/bpf/verifier.c

@@ -11663,6 +11663,7 @@ static void sanitize_dead_code(struct bpf_verifier_env *env)
 		if (aux_data[i].seen)
 			continue;
 		memcpy(insn + i, &trap, sizeof(trap));
+		aux_data[i].zext_dst = false;
 	}
 }
 

tools/testing/selftests/bpf/verifier/dead_code.c

@@ -159,3 +159,15 @@
 	.result = ACCEPT,
 	.retval = 2,
 },
+{
+	"dead code: zero extension",
+	.insns = {
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4),
+	BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 1),
+	BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_10, -4),
+	BPF_EXIT_INSN(),
+	},
+	.result = ACCEPT,
+	.retval = 0,
+},