On 04/05/2020 16:53, Xiaoguang Wang wrote:
> If copy_to_user() in io_uring_setup() failed, we'll leak many kernel
> resources, which could be reproduced by using mprotect to set params
At least it recycles everything upon killing the process, so that's rather not
notifying a user about a successfully installed fd. Good catch
> to PROT_READ. To fix this issue, refactor io_uring_create() a bit to
> let it return 'struct io_ring_ctx *', then when copy_to_user() failed,
> we can free kernel resource properly.
>
> Signed-off-by: Xiaoguang Wang <xiaoguang.wang@xxxxxxxxxxxxxxxxx>
> ---
> fs/io_uring.c | 45 ++++++++++++++++++++++++---------------------
> 1 file changed, 24 insertions(+), 21 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 0b91b0631173..a19885dee621 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -7761,7 +7761,8 @@ static int io_uring_get_fd(struct io_ring_ctx *ctx)
> return ret;
> }
>
> -static int io_uring_create(unsigned entries, struct io_uring_params *p)
> +static struct io_ring_ctx *io_uring_create(unsigned entries,
> + struct io_uring_params *p)
> {
> struct user_struct *user = NULL;
> struct io_ring_ctx *ctx;
> @@ -7769,10 +7770,10 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
> int ret;
>
> if (!entries)
> - return -EINVAL;
> + return ERR_PTR(-EINVAL);
> if (entries > IORING_MAX_ENTRIES) {
> if (!(p->flags & IORING_SETUP_CLAMP))
> - return -EINVAL;
> + return ERR_PTR(-EINVAL);
> entries = IORING_MAX_ENTRIES;
> }
>
> @@ -7792,10 +7793,10 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
> * any cq vs sq ring sizing.
> */
> if (p->cq_entries < p->sq_entries)
> - return -EINVAL;
> + return ERR_PTR(-EINVAL);
> if (p->cq_entries > IORING_MAX_CQ_ENTRIES) {
> if (!(p->flags & IORING_SETUP_CLAMP))
> - return -EINVAL;
> + return ERR_PTR(-EINVAL);
> p->cq_entries = IORING_MAX_CQ_ENTRIES;
> }
> p->cq_entries = roundup_pow_of_two(p->cq_entries);
> @@ -7811,7 +7812,7 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
> ring_pages(p->sq_entries, p->cq_entries));
> if (ret) {
> free_uid(user);
> - return ret;
> + return ERR_PTR(ret);
> }
> }
>
> @@ -7821,7 +7822,7 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
> io_unaccount_mem(user, ring_pages(p->sq_entries,
> p->cq_entries));
> free_uid(user);
> - return -ENOMEM;
> + return ERR_PTR(-ENOMEM);
> }
> ctx->compat = in_compat_syscall();
> ctx->account_mem = account_mem;
> @@ -7853,22 +7854,14 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
> p->cq_off.overflow = offsetof(struct io_rings, cq_overflow);
> p->cq_off.cqes = offsetof(struct io_rings, cqes);
>
> - /*
> - * Install ring fd as the very last thing, so we don't risk someone
> - * having closed it before we finish setup
> - */
> - ret = io_uring_get_fd(ctx);
> - if (ret < 0)
> - goto err;
> -
> p->features = IORING_FEAT_SINGLE_MMAP | IORING_FEAT_NODROP |
> IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS |
> IORING_FEAT_CUR_PERSONALITY | IORING_FEAT_FAST_POLL;
> trace_io_uring_create(ret, ctx, p->sq_entries, p->cq_entries, p->flags);
> - return ret;
> + return ctx;
> err:
> io_ring_ctx_wait_and_kill(ctx);
> - return ret;
> + return ERR_PTR(ret);
> }
>
> /*
> @@ -7878,6 +7871,7 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
> */
> static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
> {
> + struct io_ring_ctx *ctx;
> struct io_uring_params p;
> long ret;
> int i;
> @@ -7894,12 +7888,21 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
> IORING_SETUP_CLAMP | IORING_SETUP_ATTACH_WQ))
> return -EINVAL;
>
> - ret = io_uring_create(entries, &p);
> - if (ret < 0)
> - return ret;
> + ctx = io_uring_create(entries, &p);
> + if (IS_ERR(ctx))
> + return PTR_ERR(ctx);
>
> - if (copy_to_user(params, &p, sizeof(p)))
> + if (copy_to_user(params, &p, sizeof(p))) {
> + io_ring_ctx_wait_and_kill(ctx);
> return -EFAULT;
> + }
> + /*
> + * Install ring fd as the very last thing, so we don't risk someone
> + * having closed it before we finish setup
> + */
> + ret = io_uring_get_fd(ctx);
> + if (ret < 0)
> + io_ring_ctx_wait_and_kill(ctx);
>
> return ret;
> }
>
--
Pavel Begunkov
