openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 159 insertions, 0 deletions

diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
new file mode 100644
index 000000000..98ae8ef51
--- /dev/null
+++ b/io_uring/rsrc.h
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef IOU_RSRC_H
+#define IOU_RSRC_H
+
+#include <linux/io_uring_types.h>
+#include <linux/lockdep.h>
+
+#define IO_VEC_CACHE_SOFT_CAP		256
+
+enum {
+	IORING_RSRC_FILE		= 0,
+	IORING_RSRC_BUFFER		= 1,
+};
+
+struct io_rsrc_node {
+	unsigned char			type;
+	int				refs;
+
+	u64 tag;
+	union {
+		unsigned long file_ptr;
+		struct io_mapped_ubuf *buf;
+	};
+};
+
+enum {
+	IO_IMU_DEST	= 1 << ITER_DEST,
+	IO_IMU_SOURCE	= 1 << ITER_SOURCE,
+};
+
+enum {
+	IO_REGBUF_F_KBUF		= 1,
+};
+
+struct io_mapped_ubuf {
+	u64		ubuf;
+	size_t		len;
+	unsigned int	nr_bvecs;
+	unsigned int    folio_shift;
+	refcount_t	refs;
+	u8		flags;
+	u8		dir;
+	void		(*release)(void *);
+	void		*priv;
+	struct bio_vec	bvec[] __counted_by(nr_bvecs);
+};
+
+struct io_imu_folio_data {
+	/* Head folio can be partially included in the fixed buf */
+	unsigned int	nr_pages_head;
+	/* For non-head/tail folios, has to be fully included */
+	unsigned int	nr_pages_mid;
+	unsigned int	folio_shift;
+	unsigned int	nr_folios;
+	unsigned long	first_folio_page_idx;
+};
+
+bool io_rsrc_cache_init(struct io_ring_ctx *ctx);
+void io_rsrc_cache_free(struct io_ring_ctx *ctx);
+struct io_rsrc_node *io_rsrc_node_alloc(struct io_ring_ctx *ctx, int type);
+void io_free_rsrc_node(struct io_ring_ctx *ctx, struct io_rsrc_node *node);
+void io_rsrc_data_free(struct io_ring_ctx *ctx, struct io_rsrc_data *data);
+int io_rsrc_data_alloc(struct io_rsrc_data *data, unsigned nr);
+
+struct io_rsrc_node *io_find_buf_node(struct io_kiocb *req,
+				      unsigned issue_flags);
+int io_import_reg_buf(struct io_kiocb *req, struct iov_iter *iter,
+			u64 buf_addr, size_t len, int ddir,
+			unsigned issue_flags);
+int io_import_reg_vec(int ddir, struct iov_iter *iter,
+			struct io_kiocb *req, struct iou_vec *vec,
+			unsigned nr_iovs, unsigned issue_flags);
+int io_prep_reg_iovec(struct io_kiocb *req, struct iou_vec *iv,
+			const struct iovec __user *uvec, size_t uvec_segs);
+
+int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg);
+int io_sqe_buffers_unregister(struct io_ring_ctx *ctx);
+int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
+			    unsigned int nr_args, u64 __user *tags);
+int io_sqe_files_unregister(struct io_ring_ctx *ctx);
+int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
+			  unsigned nr_args, u64 __user *tags);
+
+int io_register_files_update(struct io_ring_ctx *ctx, void __user *arg,
+			     unsigned nr_args);
+int io_register_rsrc_update(struct io_ring_ctx *ctx, void __user *arg,
+			    unsigned size, unsigned type);
+int io_register_rsrc(struct io_ring_ctx *ctx, void __user *arg,
+			unsigned int size, unsigned int type);
+int io_validate_user_buf_range(u64 uaddr, u64 ulen);
+
+bool io_check_coalesce_buffer(struct page **page_array, int nr_pages,
+			      struct io_imu_folio_data *data);
+
+static inline struct io_rsrc_node *io_rsrc_node_lookup(struct io_rsrc_data *data,
+						       unsigned int index)
+{
+	if (index < data->nr)
+		return data->nodes[array_index_nospec(index, data->nr)];
+	return NULL;
+}
+
+static inline void io_put_rsrc_node(struct io_ring_ctx *ctx, struct io_rsrc_node *node)
+{
+	lockdep_assert_held(&ctx->uring_lock);
+	if (!--node->refs)
+		io_free_rsrc_node(ctx, node);
+}
+
+static inline bool io_reset_rsrc_node(struct io_ring_ctx *ctx,
+				      struct io_rsrc_data *data,
+				      unsigned int index)
+{
+	struct io_rsrc_node *node;
+
+	if (index >= data->nr)
+		return false;
+	index = array_index_nospec(index, data->nr);
+	node = data->nodes[index];
+	if (!node)
+		return false;
+	io_put_rsrc_node(ctx, node);
+	data->nodes[index] = NULL;
+	return true;
+}
+
+int io_files_update(struct io_kiocb *req, unsigned int issue_flags);
+int io_files_update_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+
+int __io_account_mem(struct user_struct *user, unsigned long nr_pages);
+int io_account_mem(struct user_struct *user, struct mm_struct *mm_account,
+		   unsigned long nr_pages);
+void io_unaccount_mem(struct user_struct *user, struct mm_struct *mm_account,
+		      unsigned long nr_pages);
+
+static inline void __io_unaccount_mem(struct user_struct *user,
+				      unsigned long nr_pages)
+{
+	atomic_long_sub(nr_pages, &user->locked_vm);
+}
+
+void io_vec_free(struct iou_vec *iv);
+int io_vec_realloc(struct iou_vec *iv, unsigned nr_entries);
+
+static inline void io_vec_reset_iovec(struct iou_vec *iv,
+				      struct iovec *iovec, unsigned nr)
+{
+	io_vec_free(iv);
+	iv->iovec = iovec;
+	iv->nr = nr;
+}
+
+static inline void io_alloc_cache_vec_kasan(struct iou_vec *iv)
+{
+	if (IS_ENABLED(CONFIG_KASAN))
+		io_vec_free(iv);
+}
+
+#endif