ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faultsgrafted

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 <xiqi2@huawei.com>

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) <ljs@kernel.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Qi Xi <xiqi2@huawei.com>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 43 insertions, 0 deletions

diff --git a/drivers/block/Makefile b/drivers/block/Makefile
new file mode 100644
index 000000000..2d8096eb8
--- /dev/null
+++ b/drivers/block/Makefile
@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the kernel block device drivers.
+#
+# 12 June 2000, Christoph Hellwig <hch@infradead.org>
+# Rewritten to use lists instead of if-statements.
+# 
+
+# needed for trace events
+ccflags-y				+= -I$(src)
+
+obj-$(CONFIG_MAC_FLOPPY)	+= swim3.o
+obj-$(CONFIG_BLK_DEV_SWIM)	+= swim_mod.o
+obj-$(CONFIG_BLK_DEV_FD)	+= floppy.o
+obj-$(CONFIG_AMIGA_FLOPPY)	+= amiflop.o
+obj-$(CONFIG_PS3_DISK)		+= ps3disk.o
+obj-$(CONFIG_PS3_VRAM)		+= ps3vram.o
+obj-$(CONFIG_ATARI_FLOPPY)	+= ataflop.o
+obj-$(CONFIG_AMIGA_Z2RAM)	+= z2ram.o
+obj-$(CONFIG_N64CART)		+= n64cart.o
+obj-$(CONFIG_BLK_DEV_RAM)	+= brd.o
+obj-$(CONFIG_BLK_DEV_LOOP)	+= loop.o
+obj-$(CONFIG_SUNVDC)		+= sunvdc.o
+
+obj-$(CONFIG_BLK_DEV_NBD)	+= nbd.o
+obj-$(CONFIG_VIRTIO_BLK)	+= virtio_blk.o
+
+obj-$(CONFIG_XEN_BLKDEV_FRONTEND)	+= xen-blkfront.o
+obj-$(CONFIG_XEN_BLKDEV_BACKEND)	+= xen-blkback/
+obj-$(CONFIG_BLK_DEV_DRBD)     += drbd/
+obj-$(CONFIG_BLK_DEV_RBD)     += rbd.o
+obj-$(CONFIG_BLK_DEV_PCIESSD_MTIP32XX)	+= mtip32xx/
+
+obj-$(CONFIG_ZRAM) += zram/
+obj-$(CONFIG_BLK_DEV_RNBD)	+= rnbd/
+
+obj-$(CONFIG_BLK_DEV_NULL_BLK)	+= null_blk/
+obj-$(CONFIG_BLK_DEV_RUST_NULL) += rnull/
+
+obj-$(CONFIG_BLK_DEV_UBLK)			+= ublk_drv.o
+obj-$(CONFIG_BLK_DEV_ZONED_LOOP) += zloop.o
+
+swim_mod-y	:= swim.o swim_asm.o