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, 68 insertions, 0 deletions

diff --git a/drivers/video/logo/logo.c b/drivers/video/logo/logo.c
new file mode 100644
index 000000000..91535f884
--- /dev/null
+++ b/drivers/video/logo/logo.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ *  Linux logo to be displayed on boot
+ *
+ *  Copyright (C) 1996 Larry Ewing (lewing@isc.tamu.edu)
+ *  Copyright (C) 1996,1998 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
+ *  Copyright (C) 2001 Greg Banks <gnb@alphalink.com.au>
+ *  Copyright (C) 2001 Jan-Benedict Glaw <jbglaw@lug-owl.de>
+ *  Copyright (C) 2003 Geert Uytterhoeven <geert@linux-m68k.org>
+ */
+
+#include <linux/linux_logo.h>
+#include <linux/stddef.h>
+#include <linux/module.h>
+
+#ifdef CONFIG_M68K
+#include <asm/setup.h>
+#endif
+
+static bool nologo;
+module_param(nologo, bool, 0);
+MODULE_PARM_DESC(nologo, "Disables startup logo");
+
+/*
+ * Logos are located in the initdata, and will be freed in kernel_init.
+ * Use late_init to mark the logos as freed to prevent any further use.
+ */
+
+static bool logos_freed;
+
+static int __init fb_logo_late_init(void)
+{
+	logos_freed = true;
+	return 0;
+}
+
+late_initcall_sync(fb_logo_late_init);
+
+/* logo's are marked __initdata. Use __ref to tell
+ * modpost that it is intended that this function uses data
+ * marked __initdata.
+ */
+const struct linux_logo * __ref fb_find_logo(int depth)
+{
+	const struct linux_logo *logo = NULL;
+
+	if (nologo || logos_freed)
+		return NULL;
+
+#ifdef CONFIG_LOGO_LINUX_MONO
+	if (depth >= 1)
+		logo = &logo_linux_mono;
+#endif
+	
+#ifdef CONFIG_LOGO_LINUX_VGA16
+	if (depth >= 4)
+		logo = &logo_linux_vga16;
+#endif
+	
+#ifdef CONFIG_LOGO_LINUX_CLUT224
+	if (depth >= 8)
+		logo = &logo_linux_clut224;
+#endif
+
+	return logo;
+}
+EXPORT_SYMBOL_GPL(fb_find_logo);