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, 68 insertions, 0 deletions

diff --git a/include/net/tls_prot.h b/include/net/tls_prot.h
new file mode 100644
index 000000000..68a407564
--- /dev/null
+++ b/include/net/tls_prot.h
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates.
+ *
+ * TLS Protocol definitions
+ *
+ * From https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml
+ */
+
+#ifndef _TLS_PROT_H
+#define _TLS_PROT_H
+
+/*
+ * TLS Record protocol: ContentType
+ */
+enum {
+	TLS_RECORD_TYPE_CHANGE_CIPHER_SPEC = 20,
+	TLS_RECORD_TYPE_ALERT = 21,
+	TLS_RECORD_TYPE_HANDSHAKE = 22,
+	TLS_RECORD_TYPE_DATA = 23,
+	TLS_RECORD_TYPE_HEARTBEAT = 24,
+	TLS_RECORD_TYPE_TLS12_CID = 25,
+	TLS_RECORD_TYPE_ACK = 26,
+};
+
+/*
+ * TLS Alert protocol: AlertLevel
+ */
+enum {
+	TLS_ALERT_LEVEL_WARNING = 1,
+	TLS_ALERT_LEVEL_FATAL = 2,
+};
+
+/*
+ * TLS Alert protocol: AlertDescription
+ */
+enum {
+	TLS_ALERT_DESC_CLOSE_NOTIFY = 0,
+	TLS_ALERT_DESC_UNEXPECTED_MESSAGE = 10,
+	TLS_ALERT_DESC_BAD_RECORD_MAC = 20,
+	TLS_ALERT_DESC_RECORD_OVERFLOW = 22,
+	TLS_ALERT_DESC_HANDSHAKE_FAILURE = 40,
+	TLS_ALERT_DESC_BAD_CERTIFICATE = 42,
+	TLS_ALERT_DESC_UNSUPPORTED_CERTIFICATE = 43,
+	TLS_ALERT_DESC_CERTIFICATE_REVOKED = 44,
+	TLS_ALERT_DESC_CERTIFICATE_EXPIRED = 45,
+	TLS_ALERT_DESC_CERTIFICATE_UNKNOWN = 46,
+	TLS_ALERT_DESC_ILLEGAL_PARAMETER = 47,
+	TLS_ALERT_DESC_UNKNOWN_CA = 48,
+	TLS_ALERT_DESC_ACCESS_DENIED = 49,
+	TLS_ALERT_DESC_DECODE_ERROR = 50,
+	TLS_ALERT_DESC_DECRYPT_ERROR = 51,
+	TLS_ALERT_DESC_TOO_MANY_CIDS_REQUESTED	= 52,
+	TLS_ALERT_DESC_PROTOCOL_VERSION = 70,
+	TLS_ALERT_DESC_INSUFFICIENT_SECURITY = 71,
+	TLS_ALERT_DESC_INTERNAL_ERROR = 80,
+	TLS_ALERT_DESC_INAPPROPRIATE_FALLBACK = 86,
+	TLS_ALERT_DESC_USER_CANCELED = 90,
+	TLS_ALERT_DESC_MISSING_EXTENSION = 109,
+	TLS_ALERT_DESC_UNSUPPORTED_EXTENSION = 110,
+	TLS_ALERT_DESC_UNRECOGNIZED_NAME = 112,
+	TLS_ALERT_DESC_BAD_CERTIFICATE_STATUS_RESPONSE = 113,
+	TLS_ALERT_DESC_UNKNOWN_PSK_IDENTITY = 115,
+	TLS_ALERT_DESC_CERTIFICATE_REQUIRED = 116,
+	TLS_ALERT_DESC_NO_APPLICATION_PROTOCOL = 120,
+};
+
+#endif /* _TLS_PROT_H */