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, 34 insertions, 0 deletions

diff --git a/scripts/context-analysis-suppression.txt b/scripts/context-analysis-suppression.txt
new file mode 100644
index 000000000..1c51b6153
--- /dev/null
+++ b/scripts/context-analysis-suppression.txt
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# The suppressions file should only match common paths such as header files.
+# For individual subsytems use Makefile directive CONTEXT_ANALYSIS := [yn].
+#
+# The suppressions are ignored when CONFIG_WARN_CONTEXT_ANALYSIS_ALL is
+# selected.
+
+[thread-safety]
+src:*arch/*/include/*
+src:*include/acpi/*
+src:*include/asm-generic/*
+src:*include/linux/*
+src:*include/net/*
+
+# Opt-in headers:
+src:*include/linux/bit_spinlock.h=emit
+src:*include/linux/cleanup.h=emit
+src:*include/linux/kref.h=emit
+src:*include/linux/list*.h=emit
+src:*include/linux/local_lock*.h=emit
+src:*include/linux/lockdep.h=emit
+src:*include/linux/mutex*.h=emit
+src:*include/linux/rcupdate.h=emit
+src:*include/linux/refcount.h=emit
+src:*include/linux/rhashtable.h=emit
+src:*include/linux/rtmutex*.h=emit
+src:*include/linux/rwlock*.h=emit
+src:*include/linux/rwsem.h=emit
+src:*include/linux/sched*=emit
+src:*include/linux/seqlock*.h=emit
+src:*include/linux/spinlock*.h=emit
+src:*include/linux/srcu*.h=emit
+src:*include/linux/ww_mutex.h=emit