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, 51 insertions, 0 deletions

diff --git a/include/sound/util_mem.h b/include/sound/util_mem.h
new file mode 100644
index 000000000..01310e089
--- /dev/null
+++ b/include/sound/util_mem.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __SOUND_UTIL_MEM_H
+#define __SOUND_UTIL_MEM_H
+
+#include <linux/mutex.h>
+/*
+ *  Copyright (C) 2000 Takashi Iwai <tiwai@suse.de>
+ *
+ *  Generic memory management routines for soundcard memory allocation
+ */
+
+/*
+ * memory block
+ */
+struct snd_util_memblk {
+	unsigned int size;		/* size of this block */
+	unsigned int offset;		/* zero-offset of this block */
+	struct list_head list;		/* link */
+};
+
+#define snd_util_memblk_argptr(blk)	(void*)((char*)(blk) + sizeof(struct snd_util_memblk))
+
+/*
+ * memory management information
+ */
+struct snd_util_memhdr {
+	unsigned int size;		/* size of whole data */
+	struct list_head block;		/* block linked-list header */
+	int nblocks;			/* # of allocated blocks */
+	unsigned int used;		/* used memory size */
+	int block_extra_size;		/* extra data size of chunk */
+	struct mutex block_mutex;	/* lock */
+};
+
+/*
+ * prototypes
+ */
+struct snd_util_memhdr *snd_util_memhdr_new(int memsize);
+void snd_util_memhdr_free(struct snd_util_memhdr *hdr);
+struct snd_util_memblk *snd_util_mem_alloc(struct snd_util_memhdr *hdr, int size);
+int snd_util_mem_free(struct snd_util_memhdr *hdr, struct snd_util_memblk *blk);
+int snd_util_mem_avail(struct snd_util_memhdr *hdr);
+
+/* functions without mutex */
+struct snd_util_memblk *__snd_util_mem_alloc(struct snd_util_memhdr *hdr, int size);
+void __snd_util_mem_free(struct snd_util_memhdr *hdr, struct snd_util_memblk *blk);
+struct snd_util_memblk *__snd_util_memblk_new(struct snd_util_memhdr *hdr,
+					      unsigned int units,
+					      struct list_head *prev);
+
+#endif /* __SOUND_UTIL_MEM_H */