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, 90 insertions, 0 deletions

diff --git a/net/ceph/ceph_strings.c b/net/ceph/ceph_strings.c
new file mode 100644
index 000000000..355fea272
--- /dev/null
+++ b/net/ceph/ceph_strings.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Ceph string constants
+ */
+#include <linux/module.h>
+#include <linux/ceph/types.h>
+
+const char *ceph_entity_type_name(int type)
+{
+	switch (type) {
+	case CEPH_ENTITY_TYPE_MDS: return "mds";
+	case CEPH_ENTITY_TYPE_OSD: return "osd";
+	case CEPH_ENTITY_TYPE_MON: return "mon";
+	case CEPH_ENTITY_TYPE_CLIENT: return "client";
+	case CEPH_ENTITY_TYPE_AUTH: return "auth";
+	default: return "unknown";
+	}
+}
+EXPORT_SYMBOL(ceph_entity_type_name);
+
+const char *ceph_auth_proto_name(int proto)
+{
+	switch (proto) {
+	case CEPH_AUTH_UNKNOWN:
+		return "unknown";
+	case CEPH_AUTH_NONE:
+		return "none";
+	case CEPH_AUTH_CEPHX:
+		return "cephx";
+	default:
+		return "???";
+	}
+}
+
+const char *ceph_con_mode_name(int mode)
+{
+	switch (mode) {
+	case CEPH_CON_MODE_UNKNOWN:
+		return "unknown";
+	case CEPH_CON_MODE_CRC:
+		return "crc";
+	case CEPH_CON_MODE_SECURE:
+		return "secure";
+	default:
+		return "???";
+	}
+}
+
+const char *ceph_osd_op_name(int op)
+{
+	switch (op) {
+#define GENERATE_CASE(op, opcode, str)	case CEPH_OSD_OP_##op: return (str);
+__CEPH_FORALL_OSD_OPS(GENERATE_CASE)
+#undef GENERATE_CASE
+	default:
+		return "???";
+	}
+}
+
+const char *ceph_osd_watch_op_name(int o)
+{
+	switch (o) {
+	case CEPH_OSD_WATCH_OP_UNWATCH:
+		return "unwatch";
+	case CEPH_OSD_WATCH_OP_WATCH:
+		return "watch";
+	case CEPH_OSD_WATCH_OP_RECONNECT:
+		return "reconnect";
+	case CEPH_OSD_WATCH_OP_PING:
+		return "ping";
+	default:
+		return "???";
+	}
+}
+
+const char *ceph_osd_state_name(int s)
+{
+	switch (s) {
+	case CEPH_OSD_EXISTS:
+		return "exists";
+	case CEPH_OSD_UP:
+		return "up";
+	case CEPH_OSD_AUTOOUT:
+		return "autoout";
+	case CEPH_OSD_NEW:
+		return "new";
+	default:
+		return "???";
+	}
+}