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/scsi/arm/msgqueue.c | 168 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 168 insertions(+) create mode 100644 drivers/scsi/arm/msgqueue.c (limited to 'drivers/scsi/arm/msgqueue.c') diff --git a/drivers/scsi/arm/msgqueue.c b/drivers/scsi/arm/msgqueue.c new file mode 100644 index 000000000..581158313 --- /dev/null +++ b/drivers/scsi/arm/msgqueue.c @@ -0,0 +1,168 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/drivers/acorn/scsi/msgqueue.c + * + * Copyright (C) 1997-1998 Russell King + * + * message queue handling + */ +#include +#include +#include +#include + +#include "msgqueue.h" + +/* + * Function: struct msgqueue_entry *mqe_alloc(MsgQueue_t *msgq) + * Purpose : Allocate a message queue entry + * Params : msgq - message queue to claim entry for + * Returns : message queue entry or NULL. + */ +static struct msgqueue_entry *mqe_alloc(MsgQueue_t *msgq) +{ + struct msgqueue_entry *mq; + + if ((mq = msgq->free) != NULL) + msgq->free = mq->next; + + return mq; +} + +/* + * Function: void mqe_free(MsgQueue_t *msgq, struct msgqueue_entry *mq) + * Purpose : free a message queue entry + * Params : msgq - message queue to free entry from + * mq - message queue entry to free + */ +static void mqe_free(MsgQueue_t *msgq, struct msgqueue_entry *mq) +{ + if (mq) { + mq->next = msgq->free; + msgq->free = mq; + } +} + +/* + * Function: void msgqueue_initialise(MsgQueue_t *msgq) + * Purpose : initialise a message queue + * Params : msgq - queue to initialise + */ +void msgqueue_initialise(MsgQueue_t *msgq) +{ + int i; + + msgq->qe = NULL; + msgq->free = &msgq->entries[0]; + + for (i = 0; i < NR_MESSAGES; i++) + msgq->entries[i].next = &msgq->entries[i + 1]; + + msgq->entries[NR_MESSAGES - 1].next = NULL; +} + + +/* + * Function: void msgqueue_free(MsgQueue_t *msgq) + * Purpose : free a queue + * Params : msgq - queue to free + */ +void msgqueue_free(MsgQueue_t *msgq) +{ +} + +/* + * Function: int msgqueue_msglength(MsgQueue_t *msgq) + * Purpose : calculate the total length of all messages on the message queue + * Params : msgq - queue to examine + * Returns : number of bytes of messages in queue + */ +int msgqueue_msglength(MsgQueue_t *msgq) +{ + struct msgqueue_entry *mq = msgq->qe; + int length = 0; + + for (mq = msgq->qe; mq; mq = mq->next) + length += mq->msg.length; + + return length; +} + +/* + * Function: struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno) + * Purpose : return a message + * Params : msgq - queue to obtain message from + * : msgno - message number + * Returns : pointer to message string, or NULL + */ +struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno) +{ + struct msgqueue_entry *mq; + + for (mq = msgq->qe; mq && msgno; mq = mq->next, msgno--); + + return mq ? &mq->msg : NULL; +} + +/* + * Function: int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...) + * Purpose : add a message onto a message queue + * Params : msgq - queue to add message on + * length - length of message + * ... - message bytes + * Returns : != 0 if successful + */ +int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...) +{ + struct msgqueue_entry *mq = mqe_alloc(msgq); + va_list ap; + + if (mq) { + struct msgqueue_entry **mqp; + int i; + + va_start(ap, length); + for (i = 0; i < length; i++) + mq->msg.msg[i] = va_arg(ap, unsigned int); + va_end(ap); + + mq->msg.length = length; + mq->msg.fifo = 0; + mq->next = NULL; + + mqp = &msgq->qe; + while (*mqp) + mqp = &(*mqp)->next; + + *mqp = mq; + } + + return mq != NULL; +} + +/* + * Function: void msgqueue_flush(MsgQueue_t *msgq) + * Purpose : flush all messages from message queue + * Params : msgq - queue to flush + */ +void msgqueue_flush(MsgQueue_t *msgq) +{ + struct msgqueue_entry *mq, *mqnext; + + for (mq = msgq->qe; mq; mq = mqnext) { + mqnext = mq->next; + mqe_free(msgq, mq); + } + msgq->qe = NULL; +} + +EXPORT_SYMBOL(msgqueue_initialise); +EXPORT_SYMBOL(msgqueue_free); +EXPORT_SYMBOL(msgqueue_msglength); +EXPORT_SYMBOL(msgqueue_getmsg); +EXPORT_SYMBOL(msgqueue_addmsg); +EXPORT_SYMBOL(msgqueue_flush); + +MODULE_AUTHOR("Russell King"); +MODULE_DESCRIPTION("SCSI message queue handling"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1