selftests/bpf: Test packet range of pointers sharing an idgrafted

Add tests where two packet pointers share an id and tightening one
pointer's umax from its var_off would put it less than their constant
distance from the other's umax: with an index & 0x38 capped at 50, the
base pointer keeps umax 50, so the pointer 8 bytes further on must keep
umax 58, even though its known bits allow at most 56.

These refused a valid program or accepted an out-of-bounds access before
the fix:

- check the advanced copy, load through the base: valid, was refused;
- check the base, load the byte at base + 1 through a copy advanced by
  8: was accepted;
- check base + 4, load 4 bytes at base + 2 through base + 8: reads two
  bytes past the checked range, was accepted;
- the same as the second with data_meta pointers checked against data:
  was accepted.

These pass with and without the fix and cover nearby paths:

- subtract an unknown scalar from a checked pointer and load below it
  (the range is kept across a new id);
- reach a load through two paths whose checks cover 8 and 7 bytes after
  the loaded pointer; the second path must not be pruned by the first;
- spill a copy of a pointer, check the pointer, fill the copy and load
  one byte past the checked range: the load is refused, and the copy
  has the range of the check.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/lib/raid/raid6/algos.h b/lib/raid/raid6/algos.h
new file mode 100644
index 000000000..43f636be1
--- /dev/null
+++ b/lib/raid/raid6/algos.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright 2003 H. Peter Anvin - All Rights Reserved
+ */
+#ifndef _PQ_IMPL_H
+#define _PQ_IMPL_H
+
+#include <linux/init.h>
+#include <linux/raid/pq_tables.h>
+
+/* Routine choices */
+struct raid6_calls {
+	const char *name;
+	void (*gen_syndrome)(int disks, size_t bytes, void **ptrs);
+	void (*xor_syndrome)(int disks, int start, int stop, size_t bytes,
+			void **ptrs);
+};
+
+struct raid6_recov_calls {
+	const char *name;
+	void (*data2)(int disks, size_t bytes, int faila, int failb,
+			void **ptrs);
+	void (*datap)(int disks, size_t bytes, int faila, void **ptrs);
+};
+
+void __init raid6_algo_add(const struct raid6_calls *algo);
+void __init raid6_algo_add_default(void);
+void __init raid6_recov_algo_add(const struct raid6_recov_calls *algo);
+
+/* for the kunit test */
+const struct raid6_calls *raid6_algo_find(unsigned int idx);
+const struct raid6_recov_calls *raid6_recov_algo_find(unsigned int idx);
+
+/* generic implementations */
+extern const struct raid6_calls raid6_intx1;
+extern const struct raid6_calls raid6_intx2;
+extern const struct raid6_calls raid6_intx4;
+extern const struct raid6_calls raid6_intx8;
+extern const struct raid6_recov_calls raid6_recov_intx1;
+
+#endif /* _PQ_IMPL_H */