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, 115 insertions, 0 deletions

diff --git a/include/uapi/rdma/ionic-abi.h b/include/uapi/rdma/ionic-abi.h
new file mode 100644
index 000000000..7b589d3e9
--- /dev/null
+++ b/include/uapi/rdma/ionic-abi.h
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Copyright (C) 2018-2025, Advanced Micro Devices, Inc */
+
+#ifndef IONIC_ABI_H
+#define IONIC_ABI_H
+
+#include <linux/types.h>
+
+#define IONIC_ABI_VERSION	1
+
+#define IONIC_EXPDB_64		1
+#define IONIC_EXPDB_128		2
+#define IONIC_EXPDB_256		4
+#define IONIC_EXPDB_512		8
+
+#define IONIC_EXPDB_SQ		1
+#define IONIC_EXPDB_RQ		2
+
+#define IONIC_CMB_ENABLE	1
+#define IONIC_CMB_REQUIRE	2
+#define IONIC_CMB_EXPDB		4
+#define IONIC_CMB_WC		8
+#define IONIC_CMB_UC		16
+
+struct ionic_ctx_req {
+	__u32 rsvd[2];
+};
+
+struct ionic_ctx_resp {
+	__u32 rsvd;
+	__u32 page_shift;
+
+	__aligned_u64 dbell_offset;
+
+	__u16 version;
+	__u8 qp_opcodes;
+	__u8 admin_opcodes;
+
+	__u8 sq_qtype;
+	__u8 rq_qtype;
+	__u8 cq_qtype;
+	__u8 admin_qtype;
+
+	__u8 max_stride;
+	__u8 max_spec;
+	__u8 udma_count;
+	__u8 expdb_mask;
+	__u8 expdb_qtypes;
+
+	__u8 rsvd2[3];
+};
+
+struct ionic_qdesc {
+	__aligned_u64 addr;
+	__u32 size;
+	__u16 mask;
+	__u8 depth_log2;
+	__u8 stride_log2;
+};
+
+struct ionic_ah_resp {
+	__u32 ahid;
+	__u32 pad;
+};
+
+struct ionic_cq_req {
+	struct ionic_qdesc cq[2];
+	__u8 udma_mask;
+	__u8 rsvd[7];
+};
+
+struct ionic_cq_resp {
+	__u32 cqid[2];
+	__u8 udma_mask;
+	__u8 rsvd[7];
+};
+
+struct ionic_qp_req {
+	struct ionic_qdesc sq;
+	struct ionic_qdesc rq;
+	__u8 sq_spec;
+	__u8 rq_spec;
+	__u8 sq_cmb;
+	__u8 rq_cmb;
+	__u8 udma_mask;
+	__u8 rsvd[3];
+};
+
+struct ionic_qp_resp {
+	__u32 qpid;
+	__u8 sq_cmb;
+	__u8 rq_cmb;
+	__u8 udma_idx;
+	__u8 rsvd[1];
+	__aligned_u64 sq_cmb_offset;
+	__aligned_u64 rq_cmb_offset;
+};
+
+struct ionic_srq_req {
+	struct ionic_qdesc rq;
+	__u8 rq_spec;
+	__u8 rq_cmb;
+	__u8 udma_mask;
+	__u8 rsvd[5];
+};
+
+struct ionic_srq_resp {
+	__u32 qpid;
+	__u8 rq_cmb;
+	__u8 udma_idx;
+	__u8 rsvd[2];
+	__aligned_u64 rq_cmb_offset;
+};
+
+#endif /* IONIC_ABI_H */