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, 235 insertions, 0 deletions

diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
new file mode 100644
index 000000000..0755bc39b
--- /dev/null
+++ b/include/asm-generic/sections.h
@@ -0,0 +1,235 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_SECTIONS_H_
+#define _ASM_GENERIC_SECTIONS_H_
+
+/* References to section boundaries */
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+/*
+ * Usage guidelines:
+ * _text, _data: architecture specific, don't use them in arch-independent code
+ * [_stext, _etext]: contains .text.* sections, may also contain .rodata.*
+ *                   and/or .init.* sections
+ * [_sdata, _edata]: contains .data.* sections, may also contain .rodata.*
+ *                   and/or .init.* sections.
+ * [__start_rodata, __end_rodata]: contains .rodata.* sections
+ * [__start_ro_after_init, __end_ro_after_init]:
+ *		     contains .data..ro_after_init section
+ * [__init_begin, __init_end]: contains .init.* sections, but .init.text.*
+ *                   may be out of this range on some architectures.
+ * [_sinittext, _einittext]: contains .init.text.* sections
+ * [__bss_start, __bss_stop]: contains BSS sections
+ *
+ * Following global variables are optional and may be unavailable on some
+ * architectures and/or kernel configurations.
+ *	_text, _data
+ *	__kprobes_text_start, __kprobes_text_end
+ *	__entry_text_start, __entry_text_end
+ *	__ctors_start, __ctors_end
+ *	__irqentry_text_start, __irqentry_text_end
+ *	__softirqentry_text_start, __softirqentry_text_end
+ *	__start_opd, __end_opd
+ */
+extern char _text[], _stext[], _etext[];
+extern char _data[], _sdata[], _edata[];
+extern char __bss_start[], __bss_stop[];
+extern char __init_begin[], __init_end[];
+extern char _sinittext[], _einittext[];
+extern char __start_ro_after_init[], __end_ro_after_init[];
+extern char _end[];
+extern char __per_cpu_start[], __per_cpu_end[];
+extern char __kprobes_text_start[], __kprobes_text_end[];
+extern char __entry_text_start[], __entry_text_end[];
+extern char __start_rodata[], __end_rodata[];
+extern char __irqentry_text_start[], __irqentry_text_end[];
+extern char __softirqentry_text_start[], __softirqentry_text_end[];
+extern char __start_once[], __end_once[];
+
+/* Start and end of .ctors section - used for constructor calls. */
+extern char __ctors_start[], __ctors_end[];
+
+/* Start and end of .opd section - used for function descriptors. */
+extern char __start_opd[], __end_opd[];
+
+/* Start and end of instrumentation protected text section */
+extern char __noinstr_text_start[], __noinstr_text_end[];
+
+extern __visible const void __nosave_begin, __nosave_end;
+
+/* Function descriptor handling (if any).  Override in asm/sections.h */
+#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr);
+void *dereference_kernel_function_descriptor(void *ptr);
+#else
+#define dereference_function_descriptor(p) ((void *)(p))
+#define dereference_kernel_function_descriptor(p) ((void *)(p))
+
+/* An address is simply the address of the function. */
+typedef struct {
+	unsigned long addr;
+} func_desc_t;
+#endif
+
+static inline bool have_function_descriptors(void)
+{
+	return IS_ENABLED(CONFIG_HAVE_FUNCTION_DESCRIPTORS);
+}
+
+/**
+ * memory_contains - checks if an object is contained within a memory region
+ * @begin: virtual address of the beginning of the memory region
+ * @end: virtual address of the end of the memory region
+ * @virt: virtual address of the memory object
+ * @size: size of the memory object
+ *
+ * Returns: true if the object specified by @virt and @size is entirely
+ * contained within the memory region defined by @begin and @end, false
+ * otherwise.
+ */
+static inline bool memory_contains(void *begin, void *end, void *virt,
+				   size_t size)
+{
+	return virt >= begin && virt + size <= end;
+}
+
+/**
+ * memory_intersects - checks if the region occupied by an object intersects
+ *                     with another memory region
+ * @begin: virtual address of the beginning of the memory region
+ * @end: virtual address of the end of the memory region
+ * @virt: virtual address of the memory object
+ * @size: size of the memory object
+ *
+ * Returns: true if an object's memory region, specified by @virt and @size,
+ * intersects with the region specified by @begin and @end, false otherwise.
+ */
+static inline bool memory_intersects(void *begin, void *end, void *virt,
+				     size_t size)
+{
+	void *vend = virt + size;
+
+	if (virt < end && vend > begin)
+		return true;
+
+	return false;
+}
+
+/**
+ * init_section_contains - checks if an object is contained within the init
+ *                         section
+ * @virt: virtual address of the memory object
+ * @size: size of the memory object
+ *
+ * Returns: true if the object specified by @virt and @size is entirely
+ * contained within the init section, false otherwise.
+ */
+static inline bool init_section_contains(void *virt, size_t size)
+{
+	return memory_contains(__init_begin, __init_end, virt, size);
+}
+
+/**
+ * init_section_intersects - checks if the region occupied by an object
+ *                           intersects with the init section
+ * @virt: virtual address of the memory object
+ * @size: size of the memory object
+ *
+ * Returns: true if an object's memory region, specified by @virt and @size,
+ * intersects with the init section, false otherwise.
+ */
+static inline bool init_section_intersects(void *virt, size_t size)
+{
+	return memory_intersects(__init_begin, __init_end, virt, size);
+}
+
+/**
+ * is_kernel_core_data - checks if the pointer address is located in the
+ *			 .data or .bss section
+ *
+ * @addr: address to check
+ *
+ * Returns: true if the address is located in .data or .bss, false otherwise.
+ * Note: On some archs it may return true for core RODATA, and false
+ *       for others. But will always be true for core RW data.
+ */
+static inline bool is_kernel_core_data(unsigned long addr)
+{
+	if (addr >= (unsigned long)_sdata && addr < (unsigned long)_edata)
+		return true;
+
+	if (addr >= (unsigned long)__bss_start &&
+	    addr < (unsigned long)__bss_stop)
+		return true;
+
+	return false;
+}
+
+/**
+ * is_kernel_rodata - checks if the pointer address is located in the
+ *                    .rodata section
+ *
+ * @addr: address to check
+ *
+ * Returns: true if the address is located in .rodata, false otherwise.
+ */
+static inline bool is_kernel_rodata(unsigned long addr)
+{
+	return addr >= (unsigned long)__start_rodata &&
+	       addr < (unsigned long)__end_rodata;
+}
+
+static inline bool is_kernel_ro_after_init(unsigned long addr)
+{
+	return addr >= (unsigned long)__start_ro_after_init &&
+	       addr < (unsigned long)__end_ro_after_init;
+}
+/**
+ * is_kernel_inittext - checks if the pointer address is located in the
+ *                      .init.text section
+ *
+ * @addr: address to check
+ *
+ * Returns: true if the address is located in .init.text, false otherwise.
+ */
+static inline bool is_kernel_inittext(unsigned long addr)
+{
+	return addr >= (unsigned long)_sinittext &&
+	       addr < (unsigned long)_einittext;
+}
+
+/**
+ * __is_kernel_text - checks if the pointer address is located in the
+ *                    .text section
+ *
+ * @addr: address to check
+ *
+ * Returns: true if the address is located in .text, false otherwise.
+ * Note: an internal helper, only check the range of _stext to _etext.
+ */
+static inline bool __is_kernel_text(unsigned long addr)
+{
+	return addr >= (unsigned long)_stext &&
+	       addr < (unsigned long)_etext;
+}
+
+/**
+ * __is_kernel - checks if the pointer address is located in the kernel range
+ *
+ * @addr: address to check
+ *
+ * Returns: true if the address is located in the kernel range, false otherwise.
+ * Note: an internal helper, check the range of _stext to _end,
+ *       and range from __init_begin to __init_end, which can be outside
+ *       of the _stext to _end range.
+ */
+static inline bool __is_kernel(unsigned long addr)
+{
+	return ((addr >= (unsigned long)_stext &&
+	         addr < (unsigned long)_end) ||
+		(addr >= (unsigned long)__init_begin &&
+		 addr < (unsigned long)__init_end));
+}
+
+#endif /* _ASM_GENERIC_SECTIONS_H_ */