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, 408 insertions, 0 deletions

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
new file mode 100644
index 000000000..df20bdfe1
--- /dev/null
+++ b/crypto/algif_skcipher.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * algif_skcipher: User-space interface for skcipher algorithms
+ *
+ * This file provides the user-space API for symmetric key ciphers.
+ *
+ * Copyright (c) 2010 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * The following concept of the memory management is used:
+ *
+ * The kernel maintains two SGLs, the TX SGL and the RX SGL. The TX SGL is
+ * filled by user space with the data submitted via sendmsg. Filling up the TX
+ * SGL does not cause a crypto operation -- the data will only be tracked by
+ * the kernel. Upon receipt of one recvmsg call, the caller must provide a
+ * buffer which is tracked with the RX SGL.
+ *
+ * During the processing of the recvmsg operation, the cipher request is
+ * allocated and prepared. As part of the recvmsg operation, the processed
+ * TX buffers are extracted from the TX SGL into a separate SGL.
+ *
+ * After the completion of the crypto operation, the RX SGL and the cipher
+ * request is released. The extracted TX SGL parts are released together with
+ * the RX SGL release.
+ */
+
+#include <crypto/scatterwalk.h>
+#include <crypto/skcipher.h>
+#include <crypto/if_alg.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/net.h>
+#include <net/sock.h>
+
+static int skcipher_sendmsg(struct socket *sock, struct msghdr *msg,
+			    size_t size)
+{
+	struct sock *sk = sock->sk;
+	struct alg_sock *ask = alg_sk(sk);
+	struct sock *psk = ask->parent;
+	struct alg_sock *pask = alg_sk(psk);
+	struct crypto_skcipher *tfm = pask->private;
+	unsigned ivsize = crypto_skcipher_ivsize(tfm);
+
+	return af_alg_sendmsg(sock, msg, size, ivsize);
+}
+
+static int algif_skcipher_export(struct sock *sk, struct skcipher_request *req)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct crypto_skcipher *tfm;
+	struct af_alg_ctx *ctx;
+	struct alg_sock *pask;
+	unsigned statesize;
+	struct sock *psk;
+	int err;
+
+	if (!(req->base.flags & CRYPTO_SKCIPHER_REQ_NOTFINAL))
+		return 0;
+
+	ctx = ask->private;
+	psk = ask->parent;
+	pask = alg_sk(psk);
+	tfm = pask->private;
+
+	statesize = crypto_skcipher_statesize(tfm);
+	ctx->state = sock_kmalloc(sk, statesize, GFP_ATOMIC);
+	if (!ctx->state)
+		return -ENOMEM;
+
+	err = crypto_skcipher_export(req, ctx->state);
+	if (err) {
+		sock_kzfree_s(sk, ctx->state, statesize);
+		ctx->state = NULL;
+	}
+
+	return err;
+}
+
+static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
+			     size_t ignored, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct alg_sock *ask = alg_sk(sk);
+	struct sock *psk = ask->parent;
+	struct alg_sock *pask = alg_sk(psk);
+	struct af_alg_ctx *ctx = ask->private;
+	struct crypto_skcipher *tfm = pask->private;
+	unsigned int bs = crypto_skcipher_chunksize(tfm);
+	struct af_alg_async_req *areq;
+	unsigned cflags = 0;
+	int err = 0;
+	size_t len = 0;
+
+	if (!ctx->init || (ctx->more && ctx->used < bs)) {
+		err = af_alg_wait_for_data(sk, flags, bs);
+		if (err)
+			return err;
+	}
+
+	/* Allocate cipher request for current operation. */
+	areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
+				     crypto_skcipher_reqsize(tfm));
+	if (IS_ERR(areq))
+		return PTR_ERR(areq);
+
+	/* convert iovecs of output buffers into RX SGL */
+	err = af_alg_get_rsgl(sk, msg, flags, areq, ctx->used, &len);
+	if (err)
+		goto free;
+
+	/*
+	 * If more buffers are to be expected to be processed, process only
+	 * full block size buffers.
+	 */
+	if (ctx->more || len < ctx->used) {
+		if (len < bs) {
+			err = -EINVAL;
+			goto free;
+		}
+
+		len -= len % bs;
+		cflags |= CRYPTO_SKCIPHER_REQ_NOTFINAL;
+	}
+
+	/*
+	 * Create a per request TX SGL for this request which tracks the
+	 * SG entries from the global TX SGL.
+	 */
+	areq->tsgl_entries = af_alg_count_tsgl(sk, len);
+	if (!areq->tsgl_entries)
+		areq->tsgl_entries = 1;
+	areq->tsgl = sock_kmalloc(sk, array_size(sizeof(*areq->tsgl),
+						 areq->tsgl_entries),
+				  GFP_KERNEL);
+	if (!areq->tsgl) {
+		err = -ENOMEM;
+		goto free;
+	}
+	sg_init_table(areq->tsgl, areq->tsgl_entries);
+	af_alg_pull_tsgl(sk, len, areq->tsgl);
+
+	/* Initialize the crypto operation */
+	skcipher_request_set_tfm(&areq->cra_u.skcipher_req, tfm);
+	skcipher_request_set_crypt(&areq->cra_u.skcipher_req, areq->tsgl,
+				   areq->first_rsgl.sgl.sgt.sgl, len, ctx->iv);
+
+	if (ctx->state) {
+		err = crypto_skcipher_import(&areq->cra_u.skcipher_req,
+					     ctx->state);
+		sock_kzfree_s(sk, ctx->state, crypto_skcipher_statesize(tfm));
+		ctx->state = NULL;
+		if (err)
+			goto free;
+		cflags |= CRYPTO_SKCIPHER_REQ_CONT;
+	}
+
+	skcipher_request_set_callback(&areq->cra_u.skcipher_req,
+				      cflags |
+				      CRYPTO_TFM_REQ_MAY_SLEEP |
+				      CRYPTO_TFM_REQ_MAY_BACKLOG,
+				      crypto_req_done, &ctx->wait);
+	err = crypto_wait_req(ctx->enc ?
+		crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
+		crypto_skcipher_decrypt(&areq->cra_u.skcipher_req),
+					 &ctx->wait);
+
+	if (!err)
+		err = algif_skcipher_export(
+			sk, &areq->cra_u.skcipher_req);
+
+free:
+	af_alg_free_resources(areq);
+
+	return err ? err : len;
+}
+
+static int skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
+			    size_t ignored, int flags)
+{
+	struct sock *sk = sock->sk;
+	int ret = 0;
+
+	lock_sock(sk);
+	while (msg_data_left(msg)) {
+		int err = _skcipher_recvmsg(sock, msg, ignored, flags);
+
+		/*
+		 * This error covers -EIOCBQUEUED which implies that we can
+		 * only handle one AIO request. If the caller wants to have
+		 * multiple AIO requests in parallel, he must make multiple
+		 * separate AIO calls.
+		 *
+		 * Also return the error if no data has been processed so far.
+		 */
+		if (err <= 0) {
+			if (err == -EIOCBQUEUED || !ret)
+				ret = err;
+			goto out;
+		}
+
+		ret += err;
+	}
+
+out:
+	af_alg_wmem_wakeup(sk);
+	release_sock(sk);
+	return ret;
+}
+
+static struct proto_ops algif_skcipher_ops = {
+	.family		=	PF_ALG,
+
+	.connect	=	sock_no_connect,
+	.socketpair	=	sock_no_socketpair,
+	.getname	=	sock_no_getname,
+	.ioctl		=	sock_no_ioctl,
+	.listen		=	sock_no_listen,
+	.shutdown	=	sock_no_shutdown,
+	.mmap		=	sock_no_mmap,
+	.bind		=	sock_no_bind,
+	.accept		=	sock_no_accept,
+
+	.release	=	af_alg_release,
+	.sendmsg	=	skcipher_sendmsg,
+	.recvmsg	=	skcipher_recvmsg,
+	.poll		=	af_alg_poll,
+};
+
+static int skcipher_check_key(struct socket *sock)
+{
+	int err = 0;
+	struct sock *psk;
+	struct alg_sock *pask;
+	struct crypto_skcipher *tfm;
+	struct sock *sk = sock->sk;
+	struct alg_sock *ask = alg_sk(sk);
+
+	lock_sock(sk);
+	if (!atomic_read(&ask->nokey_refcnt))
+		goto unlock_child;
+
+	psk = ask->parent;
+	pask = alg_sk(ask->parent);
+	tfm = pask->private;
+
+	err = -ENOKEY;
+	lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
+	if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
+		goto unlock;
+
+	atomic_dec(&pask->nokey_refcnt);
+	atomic_set(&ask->nokey_refcnt, 0);
+
+	err = 0;
+
+unlock:
+	release_sock(psk);
+unlock_child:
+	release_sock(sk);
+
+	return err;
+}
+
+static int skcipher_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
+				  size_t size)
+{
+	int err;
+
+	err = skcipher_check_key(sock);
+	if (err)
+		return err;
+
+	return skcipher_sendmsg(sock, msg, size);
+}
+
+static int skcipher_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
+				  size_t ignored, int flags)
+{
+	int err;
+
+	err = skcipher_check_key(sock);
+	if (err)
+		return err;
+
+	return skcipher_recvmsg(sock, msg, ignored, flags);
+}
+
+static struct proto_ops algif_skcipher_ops_nokey = {
+	.family		=	PF_ALG,
+
+	.connect	=	sock_no_connect,
+	.socketpair	=	sock_no_socketpair,
+	.getname	=	sock_no_getname,
+	.ioctl		=	sock_no_ioctl,
+	.listen		=	sock_no_listen,
+	.shutdown	=	sock_no_shutdown,
+	.mmap		=	sock_no_mmap,
+	.bind		=	sock_no_bind,
+	.accept		=	sock_no_accept,
+
+	.release	=	af_alg_release,
+	.sendmsg	=	skcipher_sendmsg_nokey,
+	.recvmsg	=	skcipher_recvmsg_nokey,
+	.poll		=	af_alg_poll,
+};
+
+static void *skcipher_bind(const char *name)
+{
+	return crypto_alloc_skcipher(name, 0, AF_ALG_CRYPTOAPI_MASK);
+}
+
+static void skcipher_release(void *private)
+{
+	crypto_free_skcipher(private);
+}
+
+static int skcipher_setkey(void *private, const u8 *key, unsigned int keylen)
+{
+	return crypto_skcipher_setkey(private, key, keylen);
+}
+
+static void skcipher_sock_destruct(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct af_alg_ctx *ctx = ask->private;
+	struct sock *psk = ask->parent;
+	struct alg_sock *pask = alg_sk(psk);
+	struct crypto_skcipher *tfm = pask->private;
+
+	af_alg_pull_tsgl(sk, ctx->used, NULL);
+	sock_kzfree_s(sk, ctx->iv, crypto_skcipher_ivsize(tfm));
+	if (ctx->state)
+		sock_kzfree_s(sk, ctx->state, crypto_skcipher_statesize(tfm));
+	sock_kfree_s(sk, ctx, ctx->len);
+	af_alg_release_parent(sk);
+}
+
+static int skcipher_accept_parent_nokey(void *private, struct sock *sk)
+{
+	struct af_alg_ctx *ctx;
+	struct alg_sock *ask = alg_sk(sk);
+	struct crypto_skcipher *tfm = private;
+	unsigned int len = sizeof(*ctx);
+
+	ctx = sock_kmalloc(sk, len, GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	memset(ctx, 0, len);
+
+	ctx->iv = sock_kmalloc(sk, crypto_skcipher_ivsize(tfm),
+			       GFP_KERNEL);
+	if (!ctx->iv) {
+		sock_kfree_s(sk, ctx, len);
+		return -ENOMEM;
+	}
+	memset(ctx->iv, 0, crypto_skcipher_ivsize(tfm));
+
+	INIT_LIST_HEAD(&ctx->tsgl_list);
+	ctx->len = len;
+	crypto_init_wait(&ctx->wait);
+
+	ask->private = ctx;
+
+	sk->sk_destruct = skcipher_sock_destruct;
+
+	return 0;
+}
+
+static int skcipher_accept_parent(void *private, struct sock *sk)
+{
+	struct crypto_skcipher *tfm = private;
+
+	if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
+		return -ENOKEY;
+
+	return skcipher_accept_parent_nokey(private, sk);
+}
+
+static const struct af_alg_type algif_type_skcipher = {
+	.bind		=	skcipher_bind,
+	.release	=	skcipher_release,
+	.setkey		=	skcipher_setkey,
+	.accept		=	skcipher_accept_parent,
+	.accept_nokey	=	skcipher_accept_parent_nokey,
+	.ops		=	&algif_skcipher_ops,
+	.ops_nokey	=	&algif_skcipher_ops_nokey,
+	.name		=	"skcipher",
+	.owner		=	THIS_MODULE
+};
+
+static int __init algif_skcipher_init(void)
+{
+	return af_alg_register_type(&algif_type_skcipher);
+}
+
+static void __exit algif_skcipher_exit(void)
+{
+	int err = af_alg_unregister_type(&algif_type_skcipher);
+	BUG_ON(err);
+}
+
+module_init(algif_skcipher_init);
+module_exit(algif_skcipher_exit);
+MODULE_DESCRIPTION("Userspace interface for skcipher algorithms");
+MODULE_LICENSE("GPL");