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, 85 insertions, 0 deletions

diff --git a/include/crypto/gcm.h b/include/crypto/gcm.h
new file mode 100644
index 000000000..1d5f39ff1
--- /dev/null
+++ b/include/crypto/gcm.h
@@ -0,0 +1,85 @@
+#ifndef _CRYPTO_GCM_H
+#define _CRYPTO_GCM_H
+
+#include <linux/errno.h>
+
+#include <crypto/aes.h>
+#include <crypto/gf128hash.h>
+
+#define GCM_AES_IV_SIZE 12
+#define GCM_RFC4106_IV_SIZE 8
+#define GCM_RFC4543_IV_SIZE 8
+
+/*
+ * validate authentication tag for GCM
+ */
+static inline int crypto_gcm_check_authsize(unsigned int authsize)
+{
+	switch (authsize) {
+	case 4:
+	case 8:
+	case 12:
+	case 13:
+	case 14:
+	case 15:
+	case 16:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * validate authentication tag for RFC4106
+ */
+static inline int crypto_rfc4106_check_authsize(unsigned int authsize)
+{
+	switch (authsize) {
+	case 8:
+	case 12:
+	case 16:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * validate assoclen for RFC4106/RFC4543
+ */
+static inline int crypto_ipsec_check_assoclen(unsigned int assoclen)
+{
+	switch (assoclen) {
+	case 16:
+	case 20:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+struct aesgcm_ctx {
+	struct ghash_key	ghash_key;
+	struct aes_enckey	aes_key;
+	unsigned int		authsize;
+};
+
+int aesgcm_expandkey(struct aesgcm_ctx *ctx, const u8 *key,
+		     unsigned int keysize, unsigned int authsize);
+
+void aesgcm_encrypt(const struct aesgcm_ctx *ctx, u8 *dst, const u8 *src,
+		    int crypt_len, const u8 *assoc, int assoc_len,
+		    const u8 iv[GCM_AES_IV_SIZE], u8 *authtag);
+
+bool __must_check aesgcm_decrypt(const struct aesgcm_ctx *ctx, u8 *dst,
+				 const u8 *src, int crypt_len, const u8 *assoc,
+				 int assoc_len, const u8 iv[GCM_AES_IV_SIZE],
+				 const u8 *authtag);
+
+#endif