Commit 05b538c1 authored by Pavel Begunkov's avatar Pavel Begunkov
Browse files

io_uring: fix not locked access to fixed buf table 



We can look inside the fixed buffer table only while holding
->uring_lock, however in some cases we don't do the right async prep for
IORING_OP_{WRITE,READ}_FIXED ending up with NULL req->imu forcing making
an io-wq worker to try to resolve the fixed buffer without proper
locking.

Move req->imu setup into early req init paths, i.e. io_prep_rw(), which
is called unconditionally for rw requests and under uring_lock.

Fixes: 634d00df ("io_uring: add full-fledged dynamic buffers support")
Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
parent d11d31fc

fs/io_uring.c

+17 −17
Original line number Diff line number Diff line
@@ -3636,6 +3636,20 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe) 
	int ret;



	kiocb->ki_pos = READ_ONCE(sqe->off);

	/* used for fixed read/write too - just read unconditionally */

	req->buf_index = READ_ONCE(sqe->buf_index);



	if (req->opcode == IORING_OP_READ_FIXED ||

	    req->opcode == IORING_OP_WRITE_FIXED) {

		struct io_ring_ctx *ctx = req->ctx;

		u16 index;



		if (unlikely(req->buf_index >= ctx->nr_user_bufs))

			return -EFAULT;

		index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);

		req->imu = ctx->user_bufs[index];

		io_req_set_rsrc_node(req, ctx, 0);

	}



	ioprio = READ_ONCE(sqe->ioprio);

	if (ioprio) {
@@ -3648,12 +3662,9 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe) 
		kiocb->ki_ioprio = get_current_ioprio();

	}



	req->imu = NULL;

	req->rw.addr = READ_ONCE(sqe->addr);

	req->rw.len = READ_ONCE(sqe->len);

	req->rw.flags = READ_ONCE(sqe->rw_flags);

	/* used for fixed read/write too - just read unconditionally */

	req->buf_index = READ_ONCE(sqe->buf_index);

	return 0;

}
@@ -3785,20 +3796,9 @@ static int __io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter 
static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter,

			   unsigned int issue_flags)

{

	struct io_mapped_ubuf *imu = req->imu;

	u16 index, buf_index = req->buf_index;



	if (likely(!imu)) {

		struct io_ring_ctx *ctx = req->ctx;



		if (unlikely(buf_index >= ctx->nr_user_bufs))

	if (WARN_ON_ONCE(!req->imu))

		return -EFAULT;

		io_req_set_rsrc_node(req, ctx, issue_flags);

		index = array_index_nospec(buf_index, ctx->nr_user_bufs);

		imu = READ_ONCE(ctx->user_bufs[index]);

		req->imu = imu;

	}

	return __io_import_fixed(req, rw, iter, imu);

	return __io_import_fixed(req, rw, iter, req->imu);

}



static int io_buffer_add_list(struct io_ring_ctx *ctx,