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, 203 insertions, 0 deletions

diff --git a/lib/objpool.c b/lib/objpool.c
new file mode 100644
index 000000000..d98fadf1d
--- /dev/null
+++ b/lib/objpool.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/objpool.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/atomic.h>
+#include <linux/irqflags.h>
+#include <linux/cpumask.h>
+#include <linux/log2.h>
+
+/*
+ * objpool: ring-array based lockless MPMC/FIFO queues
+ *
+ * Copyright: wuqiang.matt@bytedance.com,mhiramat@kernel.org
+ */
+
+/* initialize percpu objpool_slot */
+static int
+objpool_init_percpu_slot(struct objpool_head *pool,
+			 struct objpool_slot *slot,
+			 int nodes, void *context,
+			 objpool_init_obj_cb objinit)
+{
+	void *obj = (void *)&slot->entries[pool->capacity];
+	int i;
+
+	/* initialize elements of percpu objpool_slot */
+	slot->mask = pool->capacity - 1;
+
+	for (i = 0; i < nodes; i++) {
+		if (objinit) {
+			int rc = objinit(obj, context);
+			if (rc)
+				return rc;
+		}
+		slot->entries[slot->tail & slot->mask] = obj;
+		obj = obj + pool->obj_size;
+		slot->tail++;
+		slot->last = slot->tail;
+		pool->nr_objs++;
+	}
+
+	return 0;
+}
+
+/* allocate and initialize percpu slots */
+static int
+objpool_init_percpu_slots(struct objpool_head *pool, int nr_objs,
+			  void *context, objpool_init_obj_cb objinit)
+{
+	int i, cpu_count = 0;
+
+	for (i = 0; i < nr_cpu_ids; i++) {
+
+		struct objpool_slot *slot;
+		int nodes, size, rc;
+
+		/* skip the cpu node which could never be present */
+		if (!cpu_possible(i))
+			continue;
+
+		/* compute how many objects to be allocated with this slot */
+		nodes = nr_objs / pool->nr_possible_cpus;
+		if (cpu_count < (nr_objs % pool->nr_possible_cpus))
+			nodes++;
+		cpu_count++;
+
+		size = struct_size(slot, entries, pool->capacity) +
+			pool->obj_size * nodes;
+
+		/*
+		 * here we allocate percpu-slot & objs together in a single
+		 * allocation to make it more compact, taking advantage of
+		 * warm caches and TLB hits. in default vmalloc is used to
+		 * reduce the pressure of kernel slab system. as we know,
+		 * mimimal size of vmalloc is one page since vmalloc would
+		 * always align the requested size to page size.
+		 * but if vmalloc fails or it is not available (e.g. GFP_ATOMIC)
+		 * allocate percpu slot with kmalloc.
+		 */
+		slot = NULL;
+
+		if ((pool->gfp & (GFP_ATOMIC | GFP_KERNEL)) != GFP_ATOMIC)
+			slot = __vmalloc_node(size, sizeof(void *), pool->gfp,
+				cpu_to_node(i), __builtin_return_address(0));
+
+		if (!slot) {
+			slot = kmalloc_node(size, pool->gfp, cpu_to_node(i));
+			if (!slot)
+				return -ENOMEM;
+		}
+		memset(slot, 0, size);
+		pool->cpu_slots[i] = slot;
+
+		/* initialize the objpool_slot of cpu node i */
+		rc = objpool_init_percpu_slot(pool, slot, nodes, context, objinit);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+/* cleanup all percpu slots of the object pool */
+static void objpool_fini_percpu_slots(struct objpool_head *pool)
+{
+	int i;
+
+	if (!pool->cpu_slots)
+		return;
+
+	for (i = 0; i < nr_cpu_ids; i++)
+		kvfree(pool->cpu_slots[i]);
+	kfree(pool->cpu_slots);
+}
+
+/* initialize object pool and pre-allocate objects */
+int objpool_init(struct objpool_head *pool, int nr_objs, int object_size,
+		gfp_t gfp, void *context, objpool_init_obj_cb objinit,
+		objpool_fini_cb release)
+{
+	int rc, capacity, slot_size;
+
+	/* check input parameters */
+	if (nr_objs <= 0 || nr_objs > OBJPOOL_NR_OBJECT_MAX ||
+	    object_size <= 0 || object_size > OBJPOOL_OBJECT_SIZE_MAX)
+		return -EINVAL;
+
+	/* align up to unsigned long size */
+	object_size = ALIGN(object_size, sizeof(long));
+
+	/* calculate capacity of percpu objpool_slot */
+	capacity = roundup_pow_of_two(nr_objs);
+	if (!capacity)
+		return -EINVAL;
+
+	/* initialize objpool pool */
+	memset(pool, 0, sizeof(struct objpool_head));
+	pool->nr_possible_cpus = num_possible_cpus();
+	pool->obj_size = object_size;
+	pool->capacity = capacity;
+	pool->gfp = gfp & ~__GFP_ZERO;
+	pool->context = context;
+	pool->release = release;
+	slot_size = nr_cpu_ids * sizeof(struct objpool_slot *);
+	pool->cpu_slots = kzalloc(slot_size, pool->gfp);
+	if (!pool->cpu_slots)
+		return -ENOMEM;
+
+	/* initialize per-cpu slots */
+	rc = objpool_init_percpu_slots(pool, nr_objs, context, objinit);
+	if (rc)
+		objpool_fini_percpu_slots(pool);
+	else
+		refcount_set(&pool->ref, pool->nr_objs + 1);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(objpool_init);
+
+/* release whole objpool forcely */
+void objpool_free(struct objpool_head *pool)
+{
+	if (!pool->cpu_slots)
+		return;
+
+	/* release percpu slots */
+	objpool_fini_percpu_slots(pool);
+
+	/* call user's cleanup callback if provided */
+	if (pool->release)
+		pool->release(pool, pool->context);
+}
+EXPORT_SYMBOL_GPL(objpool_free);
+
+/* drop the allocated object, rather reclaim it to objpool */
+int objpool_drop(void *obj, struct objpool_head *pool)
+{
+	if (!obj || !pool)
+		return -EINVAL;
+
+	if (refcount_dec_and_test(&pool->ref)) {
+		objpool_free(pool);
+		return 0;
+	}
+
+	return -EAGAIN;
+}
+EXPORT_SYMBOL_GPL(objpool_drop);
+
+/* drop unused objects and defref objpool for releasing */
+void objpool_fini(struct objpool_head *pool)
+{
+	int count = 1; /* extra ref for objpool itself */
+
+	/* drop all remained objects from objpool */
+	while (objpool_pop(pool))
+		count++;
+
+	if (refcount_sub_and_test(count, &pool->ref))
+		objpool_free(pool);
+}
+EXPORT_SYMBOL_GPL(objpool_fini);