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, 148 insertions, 0 deletions

diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
new file mode 100644
index 000000000..e104a651c
--- /dev/null
+++ b/drivers/md/dm-verity.h
@@ -0,0 +1,148 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ * Copyright (C) 2015 Google, Inc.
+ *
+ * Author: Mikulas Patocka <mpatocka@redhat.com>
+ *
+ * Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
+ */
+
+#ifndef DM_VERITY_H
+#define DM_VERITY_H
+
+#include <linux/dm-io.h>
+#include <linux/dm-bufio.h>
+#include <linux/device-mapper.h>
+#include <linux/interrupt.h>
+#include <crypto/hash.h>
+#include <crypto/sha2.h>
+
+#define DM_VERITY_MAX_LEVELS		63
+
+enum verity_mode {
+	DM_VERITY_MODE_EIO,
+	DM_VERITY_MODE_LOGGING,
+	DM_VERITY_MODE_RESTART,
+	DM_VERITY_MODE_PANIC
+};
+
+enum verity_block_type {
+	DM_VERITY_BLOCK_TYPE_DATA,
+	DM_VERITY_BLOCK_TYPE_METADATA
+};
+
+struct dm_verity_fec;
+
+struct dm_verity {
+	struct dm_dev *data_dev;
+	struct dm_dev *hash_dev;
+	struct dm_target *ti;
+	struct dm_bufio_client *bufio;
+	char *alg_name;
+	struct crypto_shash *shash_tfm;
+	u8 *root_digest;	/* digest of the root block */
+	u8 *salt;		/* salt: its size is salt_size */
+	union {
+		struct sha256_ctx *sha256;	/* for use_sha256_lib=1 */
+		u8 *shash;			/* for use_sha256_lib=0 */
+	} initial_hashstate; /* salted initial state, if version >= 1 */
+	u8 *zero_digest;	/* digest for a zero block */
+#ifdef CONFIG_SECURITY
+	u8 *root_digest_sig;	/* signature of the root digest */
+	unsigned int sig_size;	/* root digest signature size */
+#endif /* CONFIG_SECURITY */
+	unsigned int salt_size;
+	sector_t hash_start;	/* index of first hash block on hash_dev */
+	sector_t hash_end;	/* 1 + index of last hash block on hash dev */
+	sector_t data_blocks;	/* the number of data blocks */
+	unsigned char data_dev_block_bits;	/* log2(data blocksize) */
+	unsigned char hash_dev_block_bits;	/* log2(hash blocksize) */
+	unsigned char hash_per_block_bits;	/* log2(hashes in hash block) */
+	unsigned char levels;	/* the number of tree levels */
+	unsigned char version;
+	bool hash_failed:1;	/* set if hash of any block failed */
+	bool use_bh_wq:1;	/* try to verify in BH wq before normal work-queue */
+	bool use_sha256_lib:1;	/* use SHA-256 library instead of generic crypto API */
+	bool use_sha256_finup_2x:1; /* use interleaved hashing optimization */
+	unsigned int digest_size;	/* digest size for the current hash algorithm */
+	enum verity_mode mode;	/* mode for handling verification errors */
+	enum verity_mode error_mode;/* mode for handling I/O errors */
+	atomic_t corrupted_errs;/* Number of errors for corrupted blocks */
+
+	struct workqueue_struct *verify_wq;
+
+	/* starting blocks for each tree level. 0 is the lowest level. */
+	sector_t hash_level_block[DM_VERITY_MAX_LEVELS];
+
+	struct dm_verity_fec *fec;	/* forward error correction */
+	unsigned long *validated_blocks; /* bitset blocks validated */
+
+	char *signature_key_desc; /* signature keyring reference */
+
+	struct dm_io_client *io;
+	mempool_t recheck_pool;
+};
+
+struct pending_block {
+	void *data;
+	sector_t blkno;
+	u8 want_digest[HASH_MAX_DIGESTSIZE];
+	u8 real_digest[HASH_MAX_DIGESTSIZE];
+};
+
+struct dm_verity_io {
+	struct dm_verity *v;
+
+	/* original value of bio->bi_end_io */
+	bio_end_io_t *orig_bi_end_io;
+
+	struct bvec_iter iter;
+
+	sector_t block;
+	unsigned int n_blocks;
+	bool in_bh;
+	bool had_mismatch;
+
+#ifdef CONFIG_DM_VERITY_FEC
+	struct dm_verity_fec_io *fec_io;
+#endif
+
+	struct work_struct work;
+
+	u8 tmp_digest[HASH_MAX_DIGESTSIZE];
+
+	/*
+	 * This is the queue of data blocks that are pending verification.  When
+	 * the crypto layer supports interleaved hashing, we allow multiple
+	 * blocks to be queued up in order to utilize it.  This can improve
+	 * performance significantly vs. sequential hashing of each block.
+	 */
+	int num_pending;
+	struct pending_block pending_blocks[2];
+
+	/*
+	 * Temporary space for hashing.  Either sha256 or shash is used,
+	 * depending on the value of use_sha256_lib.  If shash is used,
+	 * then this field is variable-length, with total size
+	 * sizeof(struct shash_desc) + crypto_shash_descsize(shash_tfm).
+	 * For this reason, this field must be the end of the struct.
+	 */
+	union {
+		struct sha256_ctx sha256;
+		struct shash_desc shash;
+	} hash_ctx;
+};
+
+extern int verity_hash(struct dm_verity *v, struct dm_verity_io *io,
+		       const u8 *data, size_t len, u8 *digest);
+
+extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
+				 sector_t block, u8 *digest, bool *is_zero);
+
+extern bool dm_is_verity_target(struct dm_target *ti);
+extern int dm_verity_get_mode(struct dm_target *ti);
+extern int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest,
+				     unsigned int *digest_size);
+
+#endif /* DM_VERITY_H */