Jens Axboe <axboe@xxxxxxxxx> writes:
> For buffer registration (or updates), a userspace iovec is copied in
> and updated. If the application is within a compat syscall, then the
> iovec type is compat_iovec rather than iovec. However, the type used
> in __io_sqe_buffers_update() and io_sqe_buffers_register() is always
> struct iovec, and hence the source is incremented by the size of a
> non-compat iovec in the loop. This misses every other iovec in the
> source, and will run into garbage half way through the copies and
> return -EFAULT to the application.
>
> Maintain the source address separately and assign to our user vec
> pointer, so that copies always happen from the right source address.
>
> Fixes: f4eaf8eda89e ("io_uring/rsrc: Drop io_copy_iov in favor of iovec API")
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Thanks for the fix, Jens. please take:
Reviewed-by: Gabriel Krisman Bertazi <krisman@xxxxxxx>
>
> ---
>
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index a860516bf448..b38d0ef41ef1 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -394,10 +394,11 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
> struct io_uring_rsrc_update2 *up,
> unsigned int nr_args)
> {
> - struct iovec __user *uvec = u64_to_user_ptr(up->data);
> u64 __user *tags = u64_to_user_ptr(up->tags);
> struct iovec fast_iov, *iov;
> struct page *last_hpage = NULL;
> + struct iovec __user *uvec;
> + u64 user_data = up->data;
> __u32 done;
> int i, err;
>
> @@ -410,7 +411,8 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
> struct io_mapped_ubuf *imu;
> u64 tag = 0;
>
> - iov = iovec_from_user(&uvec[done], 1, 1, &fast_iov, ctx->compat);
> + uvec = u64_to_user_ptr(user_data);
> + iov = iovec_from_user(uvec, 1, 1, &fast_iov, ctx->compat);
> if (IS_ERR(iov)) {
> err = PTR_ERR(iov);
> break;
> @@ -443,6 +445,10 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
>
> ctx->user_bufs[i] = imu;
> *io_get_tag_slot(ctx->buf_data, i) = tag;
> + if (ctx->compat)
> + user_data += sizeof(struct compat_iovec);
> + else
> + user_data += sizeof(struct iovec);
> }
> return done ? done : err;
> }
> @@ -949,7 +955,7 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
> struct page *last_hpage = NULL;
> struct io_rsrc_data *data;
> struct iovec fast_iov, *iov = &fast_iov;
> - const struct iovec __user *uvec = (struct iovec * __user) arg;
> + const struct iovec __user *uvec;
> int i, ret;
>
> BUILD_BUG_ON(IORING_MAX_REG_BUFFERS >= (1u << 16));
> @@ -972,7 +978,8 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
>
> for (i = 0; i < nr_args; i++, ctx->nr_user_bufs++) {
> if (arg) {
> - iov = iovec_from_user(&uvec[i], 1, 1, &fast_iov, ctx->compat);
> + uvec = (struct iovec * __user) arg;
> + iov = iovec_from_user(uvec, 1, 1, &fast_iov, ctx->compat);
> if (IS_ERR(iov)) {
> ret = PTR_ERR(iov);
> break;
> @@ -980,6 +987,10 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
> ret = io_buffer_validate(iov);
> if (ret)
> break;
> + if (ctx->compat)
> + arg += sizeof(struct compat_iovec);
> + else
> + arg += sizeof(struct iovec);
> }
>
> if (!iov->iov_base && *io_get_tag_slot(data, i)) {
--
Gabriel Krisman Bertazi
