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 --- sound/firewire/packets-buffer.c | 77 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) create mode 100644 sound/firewire/packets-buffer.c (limited to 'sound/firewire/packets-buffer.c') diff --git a/sound/firewire/packets-buffer.c b/sound/firewire/packets-buffer.c new file mode 100644 index 000000000..2093a5fbd --- /dev/null +++ b/sound/firewire/packets-buffer.c @@ -0,0 +1,77 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * helpers for managing a buffer for many packets + * + * Copyright (c) Clemens Ladisch + */ + +#include +#include +#include +#include "packets-buffer.h" + +/** + * iso_packets_buffer_init - allocates the memory for packets + * @b: the buffer structure to initialize + * @unit: the device at the other end of the stream + * @count: the number of packets + * @packet_size: the (maximum) size of a packet, in bytes + * @direction: %DMA_TO_DEVICE or %DMA_FROM_DEVICE + */ +int iso_packets_buffer_init(struct iso_packets_buffer *b, struct fw_unit *unit, + unsigned int count, unsigned int packet_size, + enum dma_data_direction direction) +{ + unsigned int packets_per_page, pages; + unsigned int i, page_index, offset_in_page; + void *p; + int err; + + b->packets = kmalloc_objs(*b->packets, count); + if (!b->packets) { + err = -ENOMEM; + goto error; + } + + packet_size = L1_CACHE_ALIGN(packet_size); + packets_per_page = PAGE_SIZE / packet_size; + if (WARN_ON(!packets_per_page)) { + err = -EINVAL; + goto err_packets; + } + pages = DIV_ROUND_UP(count, packets_per_page); + + err = fw_iso_buffer_init(&b->iso_buffer, fw_parent_device(unit)->card, + pages, direction); + if (err < 0) + goto err_packets; + + for (i = 0; i < count; ++i) { + page_index = i / packets_per_page; + p = page_address(b->iso_buffer.pages[page_index]); + offset_in_page = (i % packets_per_page) * packet_size; + b->packets[i].buffer = p + offset_in_page; + b->packets[i].offset = page_index * PAGE_SIZE + offset_in_page; + } + + return 0; + +err_packets: + kfree(b->packets); +error: + return err; +} +EXPORT_SYMBOL(iso_packets_buffer_init); + +/** + * iso_packets_buffer_destroy - frees packet buffer resources + * @b: the buffer structure to free + * @unit: the device at the other end of the stream + */ +void iso_packets_buffer_destroy(struct iso_packets_buffer *b, + struct fw_unit *unit) +{ + fw_iso_buffer_destroy(&b->iso_buffer, fw_parent_device(unit)->card); + kfree(b->packets); +} +EXPORT_SYMBOL(iso_packets_buffer_destroy); -- cgit v1.3.1