Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 776 insertions, 0 deletions

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
new file mode 100644
index 000000000..7c309173d
--- /dev/null
+++ b/io_uring/kbuf.c
@@ -0,0 +1,776 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/poll.h>
+#include <linux/uio.h>
+#include <linux/vmalloc.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring.h"
+#include "opdef.h"
+#include "kbuf.h"
+#include "memmap.h"
+
+/* BIDs are addressed by a 16-bit field in a CQE */
+#define MAX_BIDS_PER_BGID (1 << 16)
+
+/* Mapped buffer ring, return io_uring_buf from head */
+#define io_ring_head_to_buf(br, head, mask)	(&(br)->bufs[(head) & (mask)])
+
+struct io_provide_buf {
+	struct file			*file;
+	__u64				addr;
+	__u32				len;
+	__u32				bgid;
+	__u32				nbufs;
+	__u16				bid;
+};
+
+static bool io_kbuf_inc_commit(struct io_buffer_list *bl, int len)
+{
+	/* No data consumed, return false early to avoid consuming the buffer */
+	if (!len)
+		return false;
+
+	while (len) {
+		struct io_uring_buf *buf;
+		u32 buf_len, this_len;
+
+		buf = io_ring_head_to_buf(bl->buf_ring, bl->head, bl->mask);
+		buf_len = READ_ONCE(buf->len);
+		this_len = min_t(u32, len, buf_len);
+		buf_len -= this_len;
+		/* Stop looping for invalid buffer length of 0 */
+		if (buf_len > bl->min_left_sub_one || !this_len) {
+			WRITE_ONCE(buf->addr, READ_ONCE(buf->addr) + this_len);
+			WRITE_ONCE(buf->len, buf_len);
+			return false;
+		}
+		WRITE_ONCE(buf->len, 0);
+		bl->head++;
+		len -= this_len;
+	}
+	return true;
+}
+
+bool io_kbuf_commit(struct io_kiocb *req,
+		    struct io_buffer_list *bl, int len, int nr)
+{
+	if (unlikely(!(req->flags & REQ_F_BUFFERS_COMMIT)))
+		return true;
+
+	req->flags &= ~REQ_F_BUFFERS_COMMIT;
+
+	if (unlikely(len < 0))
+		return true;
+	if (bl->flags & IOBL_INC)
+		return io_kbuf_inc_commit(bl, len);
+	bl->head += nr;
+	return true;
+}
+
+static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
+							unsigned int bgid)
+{
+	lockdep_assert_held(&ctx->uring_lock);
+
+	return xa_load(&ctx->io_bl_xa, bgid);
+}
+
+static int io_buffer_add_list(struct io_ring_ctx *ctx,
+			      struct io_buffer_list *bl, unsigned int bgid)
+{
+	/*
+	 * Store buffer group ID and finally mark the list as visible.
+	 * The normal lookup doesn't care about the visibility as we're
+	 * always under the ->uring_lock, but lookups from mmap do.
+	 */
+	bl->bgid = bgid;
+	guard(mutex)(&ctx->mmap_lock);
+	return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
+}
+
+void io_kbuf_drop_legacy(struct io_kiocb *req)
+{
+	if (WARN_ON_ONCE(!(req->flags & REQ_F_BUFFER_SELECTED)))
+		return;
+	req->flags &= ~REQ_F_BUFFER_SELECTED;
+	kfree(req->kbuf);
+	req->kbuf = NULL;
+}
+
+bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_buffer_list *bl;
+	struct io_buffer *buf;
+
+	io_ring_submit_lock(ctx, issue_flags);
+
+	buf = req->kbuf;
+	bl = io_buffer_get_list(ctx, buf->bgid);
+	/*
+	 * If the buffer list was upgraded to a ring-based one, or removed,
+	 * while the request was in-flight in io-wq, drop it.
+	 */
+	if (bl && !(bl->flags & IOBL_BUF_RING)) {
+		list_add(&buf->list, &bl->buf_list);
+		bl->nbufs++;
+	} else {
+		kfree(buf);
+	}
+	req->flags &= ~REQ_F_BUFFER_SELECTED;
+	req->kbuf = NULL;
+
+	io_ring_submit_unlock(ctx, issue_flags);
+	return true;
+}
+
+static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
+					      struct io_buffer_list *bl)
+{
+	if (!list_empty(&bl->buf_list)) {
+		struct io_buffer *kbuf;
+
+		kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
+		list_del(&kbuf->list);
+		bl->nbufs--;
+		if (*len == 0 || *len > kbuf->len)
+			*len = kbuf->len;
+		if (list_empty(&bl->buf_list))
+			req->flags |= REQ_F_BL_EMPTY;
+		req->flags |= REQ_F_BUFFER_SELECTED;
+		req->kbuf = kbuf;
+		req->buf_index = kbuf->bid;
+		return u64_to_user_ptr(kbuf->addr);
+	}
+	return NULL;
+}
+
+static int io_provided_buffers_select(struct io_kiocb *req, size_t *len,
+				      struct io_buffer_list *bl,
+				      struct iovec *iov)
+{
+	void __user *buf;
+
+	buf = io_provided_buffer_select(req, len, bl);
+	if (unlikely(!buf))
+		return -ENOBUFS;
+
+	iov[0].iov_base = buf;
+	iov[0].iov_len = *len;
+	return 1;
+}
+
+static bool io_should_commit(struct io_kiocb *req, unsigned int issue_flags)
+{
+	/*
+	* If we came in unlocked, we have no choice but to consume the
+	* buffer here, otherwise nothing ensures that the buffer won't
+	* get used by others. This does mean it'll be pinned until the
+	* IO completes, coming in unlocked means we're being called from
+	* io-wq context and there may be further retries in async hybrid
+	* mode. For the locked case, the caller must call commit when
+	* the transfer completes (or if we get -EAGAIN and must poll of
+	* retry).
+	*/
+	if (issue_flags & IO_URING_F_UNLOCKED)
+		return true;
+
+	/* uring_cmd commits kbuf upfront, no need to auto-commit */
+	if (!io_file_can_poll(req) && !io_is_uring_cmd(req))
+		return true;
+	return false;
+}
+
+static struct io_br_sel io_ring_buffer_select(struct io_kiocb *req, size_t *len,
+					      struct io_buffer_list *bl,
+					      unsigned int issue_flags)
+{
+	struct io_uring_buf_ring *br = bl->buf_ring;
+	__u16 tail, head = bl->head;
+	struct io_br_sel sel = { };
+	struct io_uring_buf *buf;
+	u32 buf_len;
+
+	tail = smp_load_acquire(&br->tail);
+	if (unlikely(tail == head))
+		return sel;
+
+	if (head + 1 == tail)
+		req->flags |= REQ_F_BL_EMPTY;
+
+	buf = io_ring_head_to_buf(br, head, bl->mask);
+	buf_len = READ_ONCE(buf->len);
+	if (*len == 0 || *len > buf_len)
+		*len = buf_len;
+	sel.addr = u64_to_user_ptr(READ_ONCE(buf->addr));
+	if (unlikely(!access_ok(sel.addr, *len))) {
+		sel.addr = NULL;
+		return sel;
+	}
+	req->flags |= REQ_F_BUFFER_RING | REQ_F_BUFFERS_COMMIT;
+	req->buf_index = READ_ONCE(buf->bid);
+	sel.buf_list = bl;
+
+	if (io_should_commit(req, issue_flags)) {
+		if (!io_kbuf_commit(req, sel.buf_list, *len, 1))
+			req->flags |= REQ_F_BUF_MORE;
+		sel.buf_list = NULL;
+	}
+	return sel;
+}
+
+struct io_br_sel io_buffer_select(struct io_kiocb *req, size_t *len,
+				  unsigned buf_group, unsigned int issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_br_sel sel = { };
+	struct io_buffer_list *bl;
+
+	io_ring_submit_lock(ctx, issue_flags);
+
+	bl = io_buffer_get_list(ctx, buf_group);
+	if (likely(bl)) {
+		if (bl->flags & IOBL_BUF_RING)
+			sel = io_ring_buffer_select(req, len, bl, issue_flags);
+		else
+			sel.addr = io_provided_buffer_select(req, len, bl);
+	}
+	io_ring_submit_unlock(ctx, issue_flags);
+	return sel;
+}
+
+/* cap it at a reasonable 256, will be one page even for 4K */
+#define PEEK_MAX_IMPORT		256
+
+static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
+				struct io_buffer_list *bl)
+{
+	struct io_uring_buf_ring *br = bl->buf_ring;
+	struct iovec *org_iovs = arg->iovs;
+	struct iovec *iov = arg->iovs;
+	int nr_iovs = arg->nr_iovs;
+	__u16 nr_avail, tail, head;
+	struct io_uring_buf *buf;
+
+	tail = smp_load_acquire(&br->tail);
+	head = bl->head;
+	nr_avail = min_t(__u16, tail - head, UIO_MAXIOV);
+	if (unlikely(!nr_avail))
+		return -ENOBUFS;
+
+	/* MAX_RW_COUNT is the universal Linux per-call IO maximum */
+	arg->max_len = min_t(size_t, arg->max_len, MAX_RW_COUNT);
+
+	buf = io_ring_head_to_buf(br, head, bl->mask);
+	if (arg->max_len) {
+		u32 len = READ_ONCE(buf->len);
+		size_t needed;
+
+		if (unlikely(!len))
+			return -ENOBUFS;
+		needed = (arg->max_len + len - 1) / len;
+		needed = min_not_zero(needed, (size_t) PEEK_MAX_IMPORT);
+		if (nr_avail > needed)
+			nr_avail = needed;
+	}
+
+	/*
+	 * only alloc a bigger array if we know we have data to map, eg not
+	 * a speculative peek operation.
+	 */
+	if (arg->mode & KBUF_MODE_EXPAND && nr_avail > nr_iovs && arg->max_len) {
+		iov = kmalloc_objs(struct iovec, nr_avail);
+		if (unlikely(!iov))
+			return -ENOMEM;
+		arg->iovs = iov;
+		nr_iovs = nr_avail;
+	} else if (nr_avail < nr_iovs) {
+		nr_iovs = nr_avail;
+	}
+
+	/* set it to max, if not set, so we can use it unconditionally */
+	if (!arg->max_len)
+		arg->max_len = MAX_RW_COUNT;
+
+	req->buf_index = READ_ONCE(buf->bid);
+	do {
+		u32 len = READ_ONCE(buf->len);
+
+		/* truncate end piece, if needed, for non partial buffers */
+		if (len > arg->max_len) {
+			len = arg->max_len;
+			if (!(bl->flags & IOBL_INC)) {
+				arg->partial_map = 1;
+				if (iov != arg->iovs)
+					break;
+			}
+		}
+
+		iov->iov_base = u64_to_user_ptr(READ_ONCE(buf->addr));
+		iov->iov_len = len;
+		if (unlikely(!access_ok(iov->iov_base, len))) {
+			if (arg->iovs != org_iovs)
+				kfree(arg->iovs);
+			return -EFAULT;
+		}
+		iov++;
+
+		arg->out_len += len;
+		arg->max_len -= len;
+		if (!arg->max_len)
+			break;
+
+		buf = io_ring_head_to_buf(br, ++head, bl->mask);
+	} while (--nr_iovs);
+
+	if (arg->iovs != org_iovs && (arg->mode & KBUF_MODE_FREE))
+		kfree(org_iovs);
+
+	if (head == tail)
+		req->flags |= REQ_F_BL_EMPTY;
+
+	req->flags |= REQ_F_BUFFER_RING;
+	return iov - arg->iovs;
+}
+
+int io_buffers_select(struct io_kiocb *req, struct buf_sel_arg *arg,
+		      struct io_br_sel *sel, unsigned int issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	int ret = -ENOENT;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	sel->buf_list = io_buffer_get_list(ctx, arg->buf_group);
+	if (unlikely(!sel->buf_list))
+		goto out_unlock;
+
+	if (sel->buf_list->flags & IOBL_BUF_RING) {
+		ret = io_ring_buffers_peek(req, arg, sel->buf_list);
+		/*
+		 * Don't recycle these buffers if we need to go through poll.
+		 * Nobody else can use them anyway, and holding on to provided
+		 * buffers for a send/write operation would happen on the app
+		 * side anyway with normal buffers. Besides, we already
+		 * committed them, they cannot be put back in the queue.
+		 */
+		if (ret > 0) {
+			req->flags |= REQ_F_BUFFERS_COMMIT | REQ_F_BL_NO_RECYCLE;
+			if (!io_kbuf_commit(req, sel->buf_list, arg->out_len, ret))
+				req->flags |= REQ_F_BUF_MORE;
+		}
+	} else {
+		ret = io_provided_buffers_select(req, &arg->out_len, sel->buf_list, arg->iovs);
+	}
+out_unlock:
+	if (issue_flags & IO_URING_F_UNLOCKED) {
+		sel->buf_list = NULL;
+		mutex_unlock(&ctx->uring_lock);
+	}
+	return ret;
+}
+
+int io_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
+		    struct io_br_sel *sel)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_buffer_list *bl;
+	int ret;
+
+	lockdep_assert_held(&ctx->uring_lock);
+
+	bl = io_buffer_get_list(ctx, arg->buf_group);
+	if (unlikely(!bl))
+		return -ENOENT;
+
+	if (bl->flags & IOBL_BUF_RING) {
+		ret = io_ring_buffers_peek(req, arg, bl);
+		if (ret > 0)
+			req->flags |= REQ_F_BUFFERS_COMMIT;
+		sel->buf_list = bl;
+		return ret;
+	}
+
+	/* don't support multiple buffer selections for legacy */
+	sel->buf_list = NULL;
+	return io_provided_buffers_select(req, &arg->max_len, bl, arg->iovs);
+}
+
+static inline bool __io_put_kbuf_ring(struct io_kiocb *req,
+				      struct io_buffer_list *bl, int len, int nr)
+{
+	bool ret = true;
+
+	if (bl)
+		ret = io_kbuf_commit(req, bl, len, nr);
+	if (ret && (req->flags & REQ_F_BUF_MORE))
+		ret = false;
+
+	req->flags &= ~(REQ_F_BUFFER_RING | REQ_F_BUF_MORE);
+	return ret;
+}
+
+unsigned int __io_put_kbufs(struct io_kiocb *req, struct io_buffer_list *bl,
+			    int len, int nbufs)
+{
+	unsigned int ret;
+
+	ret = IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);
+
+	if (unlikely(!(req->flags & REQ_F_BUFFER_RING))) {
+		io_kbuf_drop_legacy(req);
+		return ret;
+	}
+
+	if (!__io_put_kbuf_ring(req, bl, len, nbufs))
+		ret |= IORING_CQE_F_BUF_MORE;
+	return ret;
+}
+
+static int io_remove_buffers_legacy(struct io_ring_ctx *ctx,
+				    struct io_buffer_list *bl,
+				    unsigned long nbufs)
+{
+	unsigned long i = 0;
+	struct io_buffer *nxt;
+
+	/* protects io_buffers_cache */
+	lockdep_assert_held(&ctx->uring_lock);
+	WARN_ON_ONCE(bl->flags & IOBL_BUF_RING);
+
+	for (i = 0; i < nbufs && !list_empty(&bl->buf_list); i++) {
+		nxt = list_first_entry(&bl->buf_list, struct io_buffer, list);
+		list_del(&nxt->list);
+		bl->nbufs--;
+		kfree(nxt);
+		cond_resched();
+	}
+	return i;
+}
+
+static void io_put_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
+{
+	if (bl->flags & IOBL_BUF_RING)
+		io_free_region(ctx->user, &bl->region);
+	else
+		io_remove_buffers_legacy(ctx, bl, -1U);
+
+	kfree(bl);
+}
+
+void io_destroy_buffers(struct io_ring_ctx *ctx)
+{
+	struct io_buffer_list *bl;
+
+	while (1) {
+		unsigned long index = 0;
+
+		scoped_guard(mutex, &ctx->mmap_lock) {
+			bl = xa_find(&ctx->io_bl_xa, &index, ULONG_MAX, XA_PRESENT);
+			if (bl)
+				xa_erase(&ctx->io_bl_xa, bl->bgid);
+		}
+		if (!bl)
+			break;
+		io_put_bl(ctx, bl);
+	}
+}
+
+static void io_destroy_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
+{
+	scoped_guard(mutex, &ctx->mmap_lock)
+		WARN_ON_ONCE(xa_erase(&ctx->io_bl_xa, bl->bgid) != bl);
+	io_put_bl(ctx, bl);
+}
+
+int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
+	u64 tmp;
+
+	if (sqe->rw_flags || sqe->addr || sqe->len || sqe->off ||
+	    sqe->splice_fd_in)
+		return -EINVAL;
+
+	tmp = READ_ONCE(sqe->fd);
+	if (!tmp || tmp > MAX_BIDS_PER_BGID)
+		return -EINVAL;
+
+	memset(p, 0, sizeof(*p));
+	p->nbufs = tmp;
+	p->bgid = READ_ONCE(sqe->buf_group);
+	return 0;
+}
+
+int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	unsigned long size, tmp_check;
+	struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
+	u64 tmp;
+
+	if (sqe->rw_flags || sqe->splice_fd_in)
+		return -EINVAL;
+
+	tmp = READ_ONCE(sqe->fd);
+	if (!tmp || tmp > MAX_BIDS_PER_BGID)
+		return -E2BIG;
+	p->nbufs = tmp;
+	p->addr = READ_ONCE(sqe->addr);
+	p->len = READ_ONCE(sqe->len);
+	if (!p->len)
+		return -EINVAL;
+
+	if (check_mul_overflow((unsigned long)p->len, (unsigned long)p->nbufs,
+				&size))
+		return -EOVERFLOW;
+	if (check_add_overflow((unsigned long)p->addr, size, &tmp_check))
+		return -EOVERFLOW;
+	if (!access_ok(u64_to_user_ptr(p->addr), size))
+		return -EFAULT;
+
+	p->bgid = READ_ONCE(sqe->buf_group);
+	tmp = READ_ONCE(sqe->off);
+	if (tmp > USHRT_MAX)
+		return -E2BIG;
+	if (tmp + p->nbufs > MAX_BIDS_PER_BGID)
+		return -EINVAL;
+	p->bid = tmp;
+	return 0;
+}
+
+static int io_add_buffers(struct io_ring_ctx *ctx, struct io_provide_buf *pbuf,
+			  struct io_buffer_list *bl)
+{
+	struct io_buffer *buf;
+	u64 addr = pbuf->addr;
+	int ret = -ENOMEM, i, bid = pbuf->bid;
+
+	for (i = 0; i < pbuf->nbufs; i++) {
+		/*
+		 * Nonsensical to have more than MAX_BIDS_PER_BGID buffers in a
+		 * buffer list, as the application then has no way of knowing
+		 * which duplicate bid refers to what buffer.
+		 */
+		if (bl->nbufs == MAX_BIDS_PER_BGID) {
+			ret = -EOVERFLOW;
+			break;
+		}
+		buf = kmalloc_obj(*buf, GFP_KERNEL_ACCOUNT);
+		if (!buf)
+			break;
+
+		list_add_tail(&buf->list, &bl->buf_list);
+		bl->nbufs++;
+		buf->addr = addr;
+		buf->len = min_t(__u32, pbuf->len, MAX_RW_COUNT);
+		buf->bid = bid;
+		buf->bgid = pbuf->bgid;
+		addr += pbuf->len;
+		bid++;
+		cond_resched();
+	}
+
+	return i ? 0 : ret;
+}
+
+static int __io_manage_buffers_legacy(struct io_kiocb *req,
+					struct io_buffer_list *bl)
+{
+	struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
+	int ret;
+
+	if (!bl) {
+		if (req->opcode != IORING_OP_PROVIDE_BUFFERS)
+			return -ENOENT;
+		bl = kzalloc_obj(*bl, GFP_KERNEL_ACCOUNT);
+		if (!bl)
+			return -ENOMEM;
+
+		INIT_LIST_HEAD(&bl->buf_list);
+		ret = io_buffer_add_list(req->ctx, bl, p->bgid);
+		if (ret) {
+			kfree(bl);
+			return ret;
+		}
+	}
+	/* can't use provide/remove buffers command on mapped buffers */
+	if (bl->flags & IOBL_BUF_RING)
+		return -EINVAL;
+	if (req->opcode == IORING_OP_PROVIDE_BUFFERS)
+		return io_add_buffers(req->ctx, p, bl);
+	return io_remove_buffers_legacy(req->ctx, bl, p->nbufs);
+}
+
+int io_manage_buffers_legacy(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_buffer_list *bl;
+	int ret;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	bl = io_buffer_get_list(ctx, p->bgid);
+	ret = __io_manage_buffers_legacy(req, bl);
+	io_ring_submit_unlock(ctx, issue_flags);
+
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
+{
+	struct io_uring_buf_reg reg;
+	struct io_buffer_list *bl;
+	struct io_uring_region_desc rd;
+	struct io_uring_buf_ring *br;
+	unsigned long mmap_offset;
+	unsigned long ring_size;
+	int ret;
+
+	lockdep_assert_held(&ctx->uring_lock);
+
+	if (copy_from_user(&reg, arg, sizeof(reg)))
+		return -EFAULT;
+	if (!mem_is_zero(reg.resv, sizeof(reg.resv)))
+		return -EINVAL;
+	if (reg.flags & ~(IOU_PBUF_RING_MMAP | IOU_PBUF_RING_INC))
+		return -EINVAL;
+	if (!is_power_of_2(reg.ring_entries))
+		return -EINVAL;
+	/* cannot disambiguate full vs empty due to head/tail size */
+	if (reg.ring_entries >= 65536)
+		return -EINVAL;
+
+	/* minimum left byte count is a property of incremental buffers */
+	if (!(reg.flags & IOU_PBUF_RING_INC) && reg.min_left)
+		return -EINVAL;
+
+	bl = io_buffer_get_list(ctx, reg.bgid);
+	if (bl) {
+		/* if mapped buffer ring OR classic exists, don't allow */
+		if (bl->flags & IOBL_BUF_RING || !list_empty(&bl->buf_list))
+			return -EEXIST;
+		io_destroy_bl(ctx, bl);
+	}
+
+	bl = kzalloc_obj(*bl, GFP_KERNEL_ACCOUNT);
+	if (!bl)
+		return -ENOMEM;
+
+	mmap_offset = (unsigned long)reg.bgid << IORING_OFF_PBUF_SHIFT;
+	ring_size = flex_array_size(br, bufs, reg.ring_entries);
+
+	memset(&rd, 0, sizeof(rd));
+	rd.size = PAGE_ALIGN(ring_size);
+	if (!(reg.flags & IOU_PBUF_RING_MMAP)) {
+		rd.user_addr = reg.ring_addr;
+		rd.flags |= IORING_MEM_REGION_TYPE_USER;
+	}
+	ret = io_create_region(ctx, &bl->region, &rd, mmap_offset);
+	if (ret)
+		goto fail;
+	br = io_region_get_ptr(&bl->region);
+
+#ifdef SHM_COLOUR
+	/*
+	 * On platforms that have specific aliasing requirements, SHM_COLOUR
+	 * is set and we must guarantee that the kernel and user side align
+	 * nicely. We cannot do that if IOU_PBUF_RING_MMAP isn't set and
+	 * the application mmap's the provided ring buffer. Fail the request
+	 * if we, by chance, don't end up with aligned addresses. The app
+	 * should use IOU_PBUF_RING_MMAP instead, and liburing will handle
+	 * this transparently.
+	 */
+	if (!(reg.flags & IOU_PBUF_RING_MMAP) &&
+	    ((reg.ring_addr | (unsigned long)br) & (SHM_COLOUR - 1))) {
+		ret = -EINVAL;
+		goto fail;
+	}
+#endif
+
+	bl->mask = reg.ring_entries - 1;
+	bl->flags |= IOBL_BUF_RING;
+	bl->buf_ring = br;
+	if (reg.min_left)
+		bl->min_left_sub_one = reg.min_left - 1;
+	if (reg.flags & IOU_PBUF_RING_INC)
+		bl->flags |= IOBL_INC;
+	ret = io_buffer_add_list(ctx, bl, reg.bgid);
+	if (!ret)
+		return 0;
+fail:
+	io_free_region(ctx->user, &bl->region);
+	kfree(bl);
+	return ret;
+}
+
+int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
+{
+	struct io_uring_buf_reg reg;
+	struct io_buffer_list *bl;
+
+	lockdep_assert_held(&ctx->uring_lock);
+
+	if (copy_from_user(&reg, arg, sizeof(reg)))
+		return -EFAULT;
+	if (!mem_is_zero(reg.resv, sizeof(reg.resv)) || reg.flags)
+		return -EINVAL;
+
+	bl = io_buffer_get_list(ctx, reg.bgid);
+	if (!bl)
+		return -ENOENT;
+	if (!(bl->flags & IOBL_BUF_RING))
+		return -EINVAL;
+
+	scoped_guard(mutex, &ctx->mmap_lock)
+		xa_erase(&ctx->io_bl_xa, bl->bgid);
+
+	io_put_bl(ctx, bl);
+	return 0;
+}
+
+int io_register_pbuf_status(struct io_ring_ctx *ctx, void __user *arg)
+{
+	struct io_uring_buf_status buf_status;
+	struct io_buffer_list *bl;
+
+	if (copy_from_user(&buf_status, arg, sizeof(buf_status)))
+		return -EFAULT;
+	if (!mem_is_zero(buf_status.resv, sizeof(buf_status.resv)))
+		return -EINVAL;
+
+	bl = io_buffer_get_list(ctx, buf_status.buf_group);
+	if (!bl)
+		return -ENOENT;
+	if (!(bl->flags & IOBL_BUF_RING))
+		return -EINVAL;
+
+	buf_status.head = bl->head;
+	if (copy_to_user(arg, &buf_status, sizeof(buf_status)))
+		return -EFAULT;
+
+	return 0;
+}
+
+struct io_mapped_region *io_pbuf_get_region(struct io_ring_ctx *ctx,
+					    unsigned int bgid)
+{
+	struct io_buffer_list *bl;
+
+	lockdep_assert_held(&ctx->mmap_lock);
+
+	bl = xa_load(&ctx->io_bl_xa, bgid);
+	if (!bl || !(bl->flags & IOBL_BUF_RING))
+		return NULL;
+	return &bl->region;
+}