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, 28 insertions, 0 deletions

diff --git a/include/net/ipconfig.h b/include/net/ipconfig.h
new file mode 100644
index 000000000..8276897d0
--- /dev/null
+++ b/include/net/ipconfig.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  Copyright (C) 1997 Martin Mares
+ *
+ *  Automatic IP Layer Configuration
+ */
+
+/* The following are initdata: */
+
+#include <linux/types.h>
+
+extern int ic_proto_enabled;	/* Protocols enabled (see IC_xxx) */
+extern int ic_set_manually;	/* IPconfig parameters set manually */
+
+extern __be32 ic_myaddr;		/* My IP address */
+extern __be32 ic_gateway;		/* Gateway IP address */
+
+extern __be32 ic_servaddr;		/* Boot server IP address */
+
+extern __be32 root_server_addr;	/* Address of NFS server */
+extern u8 root_server_path[];	/* Path to mount as root */
+
+
+/* bits in ic_proto_{enabled,used} */
+#define IC_PROTO	0xFF	/* Protocols mask: */
+#define IC_BOOTP	0x01	/*   BOOTP (or DHCP, see below) */
+#define IC_RARP		0x02	/*   RARP */
+#define IC_USE_DHCP    0x100	/* If on, use DHCP instead of BOOTP */