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, 60 insertions, 0 deletions

diff --git a/drivers/crypto/caam/dpseci-debugfs.c b/drivers/crypto/caam/dpseci-debugfs.c
new file mode 100644
index 000000000..020a9d8a8
--- /dev/null
+++ b/drivers/crypto/caam/dpseci-debugfs.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
+/* Copyright 2019 NXP */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/debugfs.h>
+#include "dpseci-debugfs.h"
+
+static int dpseci_dbg_fqs_show(struct seq_file *file, void *offset)
+{
+	struct dpaa2_caam_priv *priv = file->private;
+	u32 fqid, fcnt, bcnt;
+	int i, err;
+
+	seq_printf(file, "FQ stats for %s:\n", dev_name(priv->dev));
+	seq_printf(file, "%s%16s%16s\n",
+		   "Rx-VFQID",
+		   "Pending frames",
+		   "Pending bytes");
+
+	for (i = 0; i <  priv->num_pairs; i++) {
+		fqid = priv->rx_queue_attr[i].fqid;
+		err = dpaa2_io_query_fq_count(NULL, fqid, &fcnt, &bcnt);
+		if (err)
+			continue;
+
+		seq_printf(file, "%5d%16u%16u\n", fqid, fcnt, bcnt);
+	}
+
+	seq_printf(file, "%s%16s%16s\n",
+		   "Tx-VFQID",
+		   "Pending frames",
+		   "Pending bytes");
+
+	for (i = 0; i <  priv->num_pairs; i++) {
+		fqid = priv->tx_queue_attr[i].fqid;
+		err = dpaa2_io_query_fq_count(NULL, fqid, &fcnt, &bcnt);
+		if (err)
+			continue;
+
+		seq_printf(file, "%5d%16u%16u\n", fqid, fcnt, bcnt);
+	}
+
+	return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(dpseci_dbg_fqs);
+
+void dpaa2_dpseci_debugfs_init(struct dpaa2_caam_priv *priv)
+{
+	priv->dfs_root = debugfs_create_dir(dev_name(priv->dev), NULL);
+
+	debugfs_create_file("fq_stats", 0444, priv->dfs_root, priv,
+			    &dpseci_dbg_fqs_fops);
+}
+
+void dpaa2_dpseci_debugfs_exit(struct dpaa2_caam_priv *priv)
+{
+	debugfs_remove_recursive(priv->dfs_root);
+}