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, 78 insertions, 0 deletions

diff --git a/include/scsi/iser.h b/include/scsi/iser.h
new file mode 100644
index 000000000..07a83bfa2
--- /dev/null
+++ b/include/scsi/iser.h
@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2015 Mellanox Technologies. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *	- Redistributions of source code must retain the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer.
+ *
+ *	- Redistributions in binary form must reproduce the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer in the documentation and/or other materials
+ *	  provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef ISCSI_ISER_H
+#define ISCSI_ISER_H
+
+#define ISER_ZBVA_NOT_SUP		0x80
+#define ISER_SEND_W_INV_NOT_SUP		0x40
+#define ISERT_ZBVA_NOT_USED		0x80
+#define ISERT_SEND_W_INV_NOT_USED	0x40
+
+#define ISCSI_CTRL	0x10
+#define ISER_HELLO	0x20
+#define ISER_HELLORPLY	0x30
+
+#define ISER_VER	0x10
+#define ISER_WSV	0x08
+#define ISER_RSV	0x04
+
+/**
+ * struct iser_cm_hdr - iSER CM header (from iSER Annex A12)
+ *
+ * @flags:        flags support (zbva, send_w_inv)
+ * @rsvd:         reserved
+ */
+struct iser_cm_hdr {
+	u8      flags;
+	u8      rsvd[3];
+} __packed;
+
+/**
+ * struct iser_ctrl - iSER header of iSCSI control PDU
+ *
+ * @flags:        opcode and read/write valid bits
+ * @rsvd:         reserved
+ * @write_stag:   write rkey
+ * @write_va:     write virtual address
+ * @read_stag:    read rkey
+ * @read_va:      read virtual address
+ */
+struct iser_ctrl {
+	u8      flags;
+	u8      rsvd[3];
+	__be32  write_stag;
+	__be64  write_va;
+	__be32  read_stag;
+	__be64  read_va;
+} __packed;
+
+#endif /* ISCSI_ISER_H */