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, 117 insertions, 0 deletions

diff --git a/drivers/usb/gadget/functions.c b/drivers/usb/gadget/functions.c
new file mode 100644
index 000000000..70e31c40e
--- /dev/null
+++ b/drivers/usb/gadget/functions.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/err.h>
+
+#include <linux/usb/composite.h>
+
+static LIST_HEAD(func_list);
+static DEFINE_MUTEX(func_lock);
+
+static struct usb_function_instance *try_get_usb_function_instance(const char *name)
+{
+	struct usb_function_driver *fd;
+	struct usb_function_instance *fi;
+
+	fi = ERR_PTR(-ENOENT);
+	mutex_lock(&func_lock);
+	list_for_each_entry(fd, &func_list, list) {
+
+		if (strcmp(name, fd->name))
+			continue;
+
+		if (!try_module_get(fd->mod)) {
+			fi = ERR_PTR(-EBUSY);
+			break;
+		}
+		fi = fd->alloc_inst();
+		if (IS_ERR(fi))
+			module_put(fd->mod);
+		else
+			fi->fd = fd;
+		break;
+	}
+	mutex_unlock(&func_lock);
+	return fi;
+}
+
+struct usb_function_instance *usb_get_function_instance(const char *name)
+{
+	struct usb_function_instance *fi;
+	int ret;
+
+	fi = try_get_usb_function_instance(name);
+	if (!IS_ERR(fi))
+		return fi;
+	ret = PTR_ERR(fi);
+	if (ret != -ENOENT)
+		return fi;
+	ret = request_module("usbfunc:%s", name);
+	if (ret < 0)
+		return ERR_PTR(ret);
+	return try_get_usb_function_instance(name);
+}
+EXPORT_SYMBOL_GPL(usb_get_function_instance);
+
+struct usb_function *usb_get_function(struct usb_function_instance *fi)
+{
+	struct usb_function *f;
+
+	f = fi->fd->alloc_func(fi);
+	if (IS_ERR(f))
+		return f;
+	f->fi = fi;
+	return f;
+}
+EXPORT_SYMBOL_GPL(usb_get_function);
+
+void usb_put_function_instance(struct usb_function_instance *fi)
+{
+	struct module *mod;
+
+	if (!fi || !fi->fd)
+		return;
+
+	mod = fi->fd->mod;
+	fi->free_func_inst(fi);
+	module_put(mod);
+}
+EXPORT_SYMBOL_GPL(usb_put_function_instance);
+
+void usb_put_function(struct usb_function *f)
+{
+	if (!f)
+		return;
+
+	f->free_func(f);
+}
+EXPORT_SYMBOL_GPL(usb_put_function);
+
+int usb_function_register(struct usb_function_driver *newf)
+{
+	struct usb_function_driver *fd;
+	int ret;
+
+	ret = -EEXIST;
+
+	mutex_lock(&func_lock);
+	list_for_each_entry(fd, &func_list, list) {
+		if (!strcmp(fd->name, newf->name))
+			goto out;
+	}
+	ret = 0;
+	list_add_tail(&newf->list, &func_list);
+out:
+	mutex_unlock(&func_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(usb_function_register);
+
+void usb_function_unregister(struct usb_function_driver *fd)
+{
+	mutex_lock(&func_lock);
+	list_del(&fd->list);
+	mutex_unlock(&func_lock);
+}
+EXPORT_SYMBOL_GPL(usb_function_unregister);