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, 28 insertions, 0 deletions

diff --git a/io_uring/Makefile b/io_uring/Makefile
new file mode 100644
index 000000000..c54e328d1
--- /dev/null
+++ b/io_uring/Makefile
@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for io_uring
+
+ifdef CONFIG_GCOV_PROFILE_URING
+GCOV_PROFILE := y
+endif
+
+obj-$(CONFIG_IO_URING)		+= io_uring.o opdef.o kbuf.o rsrc.o notif.o \
+					tctx.o filetable.o rw.o poll.o \
+					tw.o wait.o eventfd.o uring_cmd.o \
+					openclose.o sqpoll.o xattr.o nop.o \
+					fs.o splice.o sync.o msg_ring.o \
+					advise.o openclose.o statx.o timeout.o \
+					cancel.o waitid.o register.o \
+					truncate.o memmap.o alloc_cache.o \
+					query.o loop.o
+
+obj-$(CONFIG_IO_URING_ZCRX)	+= zcrx.o
+obj-$(CONFIG_IO_WQ)		+= io-wq.o
+obj-$(CONFIG_FUTEX)		+= futex.o
+obj-$(CONFIG_EPOLL)		+= epoll.o
+obj-$(CONFIG_NET_RX_BUSY_POLL)	+= napi.o
+obj-$(CONFIG_NET) += net.o cmd_net.o
+obj-$(CONFIG_PROC_FS) += fdinfo.o
+obj-$(CONFIG_IO_URING_MOCK_FILE) += mock_file.o
+obj-$(CONFIG_IO_URING_BPF) += bpf_filter.o
+obj-$(CONFIG_IO_URING_BPF_OPS) += bpf-ops.o