From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set, a user fault may trigger show_pte() without any lock. If another thread in the same process concurrently calls munmap(), the page table pages may be freed while show_pte() is still traversing them, causing a use-after-free in show_pte(). If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table of PMD are freed when show_pte() is running. Acquire mmap_write_lock() around show_pte() for user faults to fix the contention. For user faults, additionally restrict that show_pte() is called only when the addr is a user-space address (addr < TASK_SIZE). This is because the lock of tsk->mm only protects the virtual memory of user address space, furthermore, dumping the page tables of a kernel-space address for user faults is unnecessary and may have security implications. Keep everything unchanged for kernel faults, because the kernel is already in the "oops" state, acquiring a lock may risk a deadlock. Co-developed-by: Qi Xi Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults") Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com Acked-by: Lorenzo Stoakes (ARM) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- drivers/firewire/uapi-test.c | 90 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 drivers/firewire/uapi-test.c (limited to 'drivers/firewire/uapi-test.c') diff --git a/drivers/firewire/uapi-test.c b/drivers/firewire/uapi-test.c new file mode 100644 index 000000000..bc3f10a2e --- /dev/null +++ b/drivers/firewire/uapi-test.c @@ -0,0 +1,90 @@ +// SPDX-License-Identifier: GPL-2.0-only +// +// uapi_test.c - An application of Kunit to check layout of structures exposed to user space for +// FireWire subsystem. +// +// Copyright (c) 2023 Takashi Sakamoto + +#include +#include + +// Known issue added at v2.6.27 kernel. +static void structure_layout_event_response(struct kunit *test) +{ +#if defined(CONFIG_X86_32) + // 4 bytes alignment for aggregate type including 8 bytes storage types. + KUNIT_EXPECT_EQ(test, 20, sizeof(struct fw_cdev_event_response)); +#else + // 8 bytes alignment for aggregate type including 8 bytes storage types. + KUNIT_EXPECT_EQ(test, 24, sizeof(struct fw_cdev_event_response)); +#endif + + KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_response, closure)); + KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_response, type)); + KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_response, rcode)); + KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_response, length)); + KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_response, data)); +} + +// Added at v6.5. +static void structure_layout_event_request3(struct kunit *test) +{ + KUNIT_EXPECT_EQ(test, 56, sizeof(struct fw_cdev_event_request3)); + + KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_request3, closure)); + KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_request3, type)); + KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_request3, tcode)); + KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_request3, offset)); + KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_request3, source_node_id)); + KUNIT_EXPECT_EQ(test, 28, offsetof(struct fw_cdev_event_request3, destination_node_id)); + KUNIT_EXPECT_EQ(test, 32, offsetof(struct fw_cdev_event_request3, card)); + KUNIT_EXPECT_EQ(test, 36, offsetof(struct fw_cdev_event_request3, generation)); + KUNIT_EXPECT_EQ(test, 40, offsetof(struct fw_cdev_event_request3, handle)); + KUNIT_EXPECT_EQ(test, 44, offsetof(struct fw_cdev_event_request3, length)); + KUNIT_EXPECT_EQ(test, 48, offsetof(struct fw_cdev_event_request3, tstamp)); + KUNIT_EXPECT_EQ(test, 56, offsetof(struct fw_cdev_event_request3, data)); +} + +// Added at v6.5. +static void structure_layout_event_response2(struct kunit *test) +{ + KUNIT_EXPECT_EQ(test, 32, sizeof(struct fw_cdev_event_response2)); + + KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_response2, closure)); + KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_response2, type)); + KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_response2, rcode)); + KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_response2, length)); + KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_response2, request_tstamp)); + KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_response2, response_tstamp)); + KUNIT_EXPECT_EQ(test, 32, offsetof(struct fw_cdev_event_response2, data)); +} + +// Added at v6.5. +static void structure_layout_event_phy_packet2(struct kunit *test) +{ + KUNIT_EXPECT_EQ(test, 24, sizeof(struct fw_cdev_event_phy_packet2)); + + KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_phy_packet2, closure)); + KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_phy_packet2, type)); + KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_phy_packet2, rcode)); + KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_phy_packet2, length)); + KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_phy_packet2, tstamp)); + KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_phy_packet2, data)); +} + +static struct kunit_case structure_layout_test_cases[] = { + KUNIT_CASE(structure_layout_event_response), + KUNIT_CASE(structure_layout_event_request3), + KUNIT_CASE(structure_layout_event_response2), + KUNIT_CASE(structure_layout_event_phy_packet2), + {} +}; + +static struct kunit_suite structure_layout_test_suite = { + .name = "firewire-uapi-structure-layout", + .test_cases = structure_layout_test_cases, +}; +kunit_test_suite(structure_layout_test_suite); + +MODULE_DESCRIPTION("FireWire UAPI unit test suite"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1