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, 87 insertions, 0 deletions

diff --git a/crypto/842.c b/crypto/842.c
new file mode 100644
index 000000000..4007e87be
--- /dev/null
+++ b/crypto/842.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Cryptographic API for the 842 software compression algorithm.
+ *
+ * Copyright (C) IBM Corporation, 2011-2015
+ *
+ * Original Authors: Robert Jennings <rcj@linux.vnet.ibm.com>
+ *                   Seth Jennings <sjenning@linux.vnet.ibm.com>
+ *
+ * Rewrite: Dan Streetman <ddstreet@ieee.org>
+ *
+ * This is the software implementation of compression and decompression using
+ * the 842 format.  This uses the software 842 library at lib/842/ which is
+ * only a reference implementation, and is very, very slow as compared to other
+ * software compressors.  You probably do not want to use this software
+ * compression.  If you have access to the PowerPC 842 compression hardware, you
+ * want to use the 842 hardware compression interface, which is at:
+ * drivers/crypto/nx/nx-842-crypto.c
+ */
+
+#include <crypto/internal/scompress.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/sw842.h>
+
+static void *crypto842_alloc_ctx(void)
+{
+	void *ctx;
+
+	ctx = kmalloc(SW842_MEM_COMPRESS, GFP_KERNEL);
+	if (!ctx)
+		return ERR_PTR(-ENOMEM);
+
+	return ctx;
+}
+
+static void crypto842_free_ctx(void *ctx)
+{
+	kfree(ctx);
+}
+
+static int crypto842_scompress(struct crypto_scomp *tfm,
+			       const u8 *src, unsigned int slen,
+			       u8 *dst, unsigned int *dlen, void *ctx)
+{
+	return sw842_compress(src, slen, dst, dlen, ctx);
+}
+
+static int crypto842_sdecompress(struct crypto_scomp *tfm,
+				 const u8 *src, unsigned int slen,
+				 u8 *dst, unsigned int *dlen, void *ctx)
+{
+	return sw842_decompress(src, slen, dst, dlen);
+}
+
+static struct scomp_alg scomp = {
+	.streams		= {
+		.alloc_ctx	= crypto842_alloc_ctx,
+		.free_ctx	= crypto842_free_ctx,
+	},
+	.compress		= crypto842_scompress,
+	.decompress		= crypto842_sdecompress,
+	.base			= {
+		.cra_name	= "842",
+		.cra_driver_name = "842-scomp",
+		.cra_priority	 = 100,
+		.cra_module	 = THIS_MODULE,
+	}
+};
+
+static int __init crypto842_mod_init(void)
+{
+	return crypto_register_scomp(&scomp);
+}
+module_init(crypto842_mod_init);
+
+static void __exit crypto842_mod_exit(void)
+{
+	crypto_unregister_scomp(&scomp);
+}
+module_exit(crypto842_mod_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("842 Software Compression Algorithm");
+MODULE_ALIAS_CRYPTO("842");
+MODULE_ALIAS_CRYPTO("842-generic");
+MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");