selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 96 insertions, 0 deletions

diff --git a/usr/include/headers_check.pl b/usr/include/headers_check.pl
new file mode 100755
index 000000000..6cd6eb652
--- /dev/null
+++ b/usr/include/headers_check.pl
@@ -0,0 +1,96 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+# headers_check.pl execute a number of trivial consistency checks
+#
+# Usage: headers_check.pl dir [files...]
+# dir:   dir to look for included files
+# files: list of files to check
+#
+# The script reads the supplied files line by line and:
+#
+# 1) for each include statement it checks if the
+#    included file actually exists.
+#    Only include files located in asm* and linux* are checked.
+#    The rest are assumed to be system include files.
+#
+# 2) It is checked that prototypes does not use "extern"
+#
+# 3) Check for leaked CONFIG_ symbols
+
+use warnings;
+use strict;
+use File::Basename;
+
+my ($dir, @files) = @ARGV;
+
+my $ret = 0;
+my $line;
+my $lineno = 0;
+my $filename;
+
+foreach my $file (@files) {
+	$filename = $file;
+
+	open(my $fh, '<', $filename)
+		or die "$filename: $!\n";
+	$lineno = 0;
+	while ($line = <$fh>) {
+		$lineno++;
+		&check_include();
+		&check_asm_types();
+		&check_declarations();
+	}
+	close $fh;
+}
+exit $ret;
+
+sub check_include
+{
+	if ($line =~ m/^\s*#\s*include\s+<((asm|linux).*)>/) {
+		my $inc = $1;
+		my $found;
+		$found = stat($dir . "/" . $inc);
+		if (!$found) {
+			printf STDERR "$filename:$lineno: included file '$inc' is not exported\n";
+			$ret = 1;
+		}
+	}
+}
+
+sub check_declarations
+{
+	# soundcard.h is what it is
+	if ($line =~ m/^void seqbuf_dump\(void\);/) {
+		return;
+	}
+	# drm headers are being C++ friendly
+	if ($line =~ m/^extern "C"/) {
+		return;
+	}
+	if ($line =~ m/^(\s*extern|unsigned|char|short|int|long|void)\b/) {
+		printf STDERR "$filename:$lineno: " .
+			      "userspace cannot reference function or " .
+			      "variable defined in the kernel\n";
+		$ret = 1;
+	}
+}
+
+my $linux_asm_types;
+sub check_asm_types
+{
+	if ($filename =~ /types.h|int-l64.h|int-ll64.h/o) {
+		return;
+	}
+	if ($lineno == 1) {
+		$linux_asm_types = 0;
+	} elsif ($linux_asm_types >= 1) {
+		return;
+	}
+	if ($line =~ m/^\s*#\s*include\s+<asm\/types.h>/) {
+		$linux_asm_types = 1;
+		printf STDERR "$filename:$lineno: " .
+		"include of <linux/types.h> is preferred over <asm/types.h>\n";
+		$ret = 1;
+	}
+}