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>

13 files changed, 65 insertions, 0 deletions

diff --git a/usr/dummy-include/endian.h b/usr/dummy-include/endian.h
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/usr/dummy-include/endian.h
diff --git a/usr/dummy-include/limits.h b/usr/dummy-include/limits.h
new file mode 100644
index 000000000..49b17c10c
--- /dev/null
+++ b/usr/dummy-include/limits.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _DUMMY_LIMITS_H
+#define _DUMMY_LIMITS_H
+
+#define INT_MAX ((int)(~0U >> 1))
+#define INT_MIN (-INT_MAX - 1)
+
+#endif /* _DUMMY_LIMITS_H */
diff --git a/usr/dummy-include/netinet/if_ether.h b/usr/dummy-include/netinet/if_ether.h
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/usr/dummy-include/netinet/if_ether.h
diff --git a/usr/dummy-include/netinet/in.h b/usr/dummy-include/netinet/in.h
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/usr/dummy-include/netinet/in.h
diff --git a/usr/dummy-include/stddef.h b/usr/dummy-include/stddef.h
new file mode 100644
index 000000000..525489daf
--- /dev/null
+++ b/usr/dummy-include/stddef.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _DUMMY_STDDEF_H
+#define _DUMMY_STDDEF_H
+
+#define offsetof(TYPE, MEMBER)	__builtin_offsetof(TYPE, MEMBER)
+
+#ifdef __cplusplus
+#define NULL 0
+#else
+#define NULL ((void *)0)
+#endif
+
+#endif /* _DUMMY_STDDEF_H */
diff --git a/usr/dummy-include/stdint.h b/usr/dummy-include/stdint.h
new file mode 100644
index 000000000..93b1962fd
--- /dev/null
+++ b/usr/dummy-include/stdint.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _DUMMY_STDINT_H
+#define _DUMMY_STDINT_H
+
+#include <linux/types.h>
+
+typedef	__u64	uint64_t;
+typedef	__u32	uint32_t;
+typedef	__u16	uint16_t;
+typedef	__u8	uint8_t;
+
+typedef	__s64	int64_t;
+typedef	__s32	int32_t;
+typedef	__s16	int16_t;
+typedef	__s8	int8_t;
+
+#endif /* _DUMMY_STDINT_H */
diff --git a/usr/dummy-include/string.h b/usr/dummy-include/string.h
new file mode 100644
index 000000000..e059808d3
--- /dev/null
+++ b/usr/dummy-include/string.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _DUMMY_STRING_H
+#define _DUMMY_STRING_H
+
+#include <stddef.h>
+
+#define memset(_s, _c, _n) __builtin_memset(_s, _c, _n)
+#define memcpy(_dest, _src, _n) __builtin_memcpy(_dest, _src, _n)
+
+#define strlen(_s) __builtin_strlen(_s)
+
+#endif /* _DUMMY_STRING_H */
diff --git a/usr/dummy-include/sys/ioctl.h b/usr/dummy-include/sys/ioctl.h
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/usr/dummy-include/sys/ioctl.h
diff --git a/usr/dummy-include/sys/socket.h b/usr/dummy-include/sys/socket.h
new file mode 100644
index 000000000..748751f9e
--- /dev/null
+++ b/usr/dummy-include/sys/socket.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _DUMMY_SYS_SOCKET_H
+#define _DUMMY_SYS_SOCKET_H
+
+#include <linux/socket.h>
+
+struct sockaddr {
+	__kernel_sa_family_t	sa_family;	/* address family, AF_xxx	*/
+	char			sa_data[14];	/* 14 bytes of protocol address	*/
+};
+
+#endif /* _DUMMY_SYS_SOCKET_H */
diff --git a/usr/dummy-include/sys/time.h b/usr/dummy-include/sys/time.h
new file mode 100644
index 000000000..9817b8afb
--- /dev/null
+++ b/usr/dummy-include/sys/time.h
@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/time.h>
diff --git a/usr/dummy-include/sys/types.h b/usr/dummy-include/sys/types.h
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/usr/dummy-include/sys/types.h
diff --git a/usr/dummy-include/time.h b/usr/dummy-include/time.h
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/usr/dummy-include/time.h
diff --git a/usr/dummy-include/unistd.h b/usr/dummy-include/unistd.h
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/usr/dummy-include/unistd.h