5.4-stable review patch. If anyone has any objections, please let me know.
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From: Pavel Begunkov asml.silence@gmail.com
commit 705318a99a138c29a512a72c3e0043b3cd7f55f4 upstream.
File reference cycles have caused lots of problems for io_uring in the past, and it still doesn't work exactly right and races with unix_stream_read_generic(). The safest fix would be to completely disallow sending io_uring files via sockets via SCM_RIGHT, so there are no possible cycles invloving registered files and thus rendering SCM accounting on the io_uring side unnecessary.
Cc: stable@vger.kernel.org Fixes: 0091bfc81741b ("io_uring/af_unix: defer registered files gc to io_uring release") Reported-and-suggested-by: Jann Horn jannh@google.com Signed-off-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/c716c88321939156909cfa1bd8b0faaf1c804103.170186879... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/io_uring.c | 101 --------------------------------------------------------- net/core/scm.c | 6 +++ 2 files changed, 7 insertions(+), 100 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -3137,101 +3137,6 @@ static void io_finish_async(struct io_ri } }
-#if defined(CONFIG_UNIX) -static void io_destruct_skb(struct sk_buff *skb) -{ - struct io_ring_ctx *ctx = skb->sk->sk_user_data; - int i; - - for (i = 0; i < ARRAY_SIZE(ctx->sqo_wq); i++) - if (ctx->sqo_wq[i]) - flush_workqueue(ctx->sqo_wq[i]); - - unix_destruct_scm(skb); -} - -/* - * Ensure the UNIX gc is aware of our file set, so we are certain that - * the io_uring can be safely unregistered on process exit, even if we have - * loops in the file referencing. - */ -static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset) -{ - struct sock *sk = ctx->ring_sock->sk; - struct scm_fp_list *fpl; - struct sk_buff *skb; - int i; - - fpl = kzalloc(sizeof(*fpl), GFP_KERNEL); - if (!fpl) - return -ENOMEM; - - skb = alloc_skb(0, GFP_KERNEL); - if (!skb) { - kfree(fpl); - return -ENOMEM; - } - - skb->sk = sk; - skb->scm_io_uring = 1; - skb->destructor = io_destruct_skb; - - fpl->user = get_uid(ctx->user); - for (i = 0; i < nr; i++) { - fpl->fp[i] = get_file(ctx->user_files[i + offset]); - unix_inflight(fpl->user, fpl->fp[i]); - } - - fpl->max = fpl->count = nr; - UNIXCB(skb).fp = fpl; - refcount_add(skb->truesize, &sk->sk_wmem_alloc); - skb_queue_head(&sk->sk_receive_queue, skb); - - for (i = 0; i < nr; i++) - fput(fpl->fp[i]); - - return 0; -} - -/* - * If UNIX sockets are enabled, fd passing can cause a reference cycle which - * causes regular reference counting to break down. We rely on the UNIX - * garbage collection to take care of this problem for us. - */ -static int io_sqe_files_scm(struct io_ring_ctx *ctx) -{ - unsigned left, total; - int ret = 0; - - total = 0; - left = ctx->nr_user_files; - while (left) { - unsigned this_files = min_t(unsigned, left, SCM_MAX_FD); - - ret = __io_sqe_files_scm(ctx, this_files, total); - if (ret) - break; - left -= this_files; - total += this_files; - } - - if (!ret) - return 0; - - while (total < ctx->nr_user_files) { - fput(ctx->user_files[total]); - total++; - } - - return ret; -} -#else -static int io_sqe_files_scm(struct io_ring_ctx *ctx) -{ - return 0; -} -#endif - static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args) { @@ -3285,11 +3190,7 @@ static int io_sqe_files_register(struct return ret; }
- ret = io_sqe_files_scm(ctx); - if (ret) - io_sqe_files_unregister(ctx); - - return ret; + return 0; }
static int io_sq_offload_start(struct io_ring_ctx *ctx, --- a/net/core/scm.c +++ b/net/core/scm.c @@ -26,6 +26,7 @@ #include <linux/nsproxy.h> #include <linux/slab.h> #include <linux/errqueue.h> +#include <linux/io_uring.h>
#include <linux/uaccess.h>
@@ -103,6 +104,11 @@ static int scm_fp_copy(struct cmsghdr *c
if (fd < 0 || !(file = fget_raw(fd))) return -EBADF; + /* don't allow io_uring files */ + if (io_uring_get_socket(file)) { + fput(file); + return -EINVAL; + } *fpp++ = file; fpl->count++; }