This is a note to let you know that I've just added the patch titled io_uring: Fix XArray usage in io_uring_add_task_file to the 5.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: io_uring-fix-xarray-usage-in-io_uring_add_task_file.patch and it can be found in the queue-5.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Thu Oct 29 01:16:54 PM CET 2020 From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Date: Fri, 9 Oct 2020 13:49:52 +0100 Subject: io_uring: Fix XArray usage in io_uring_add_task_file From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> commit 236434c3438c4da3dfbd6aeeab807577b85e951a upstream. The xas_store() wasn't paired with an xas_nomem() loop, so if it couldn't allocate memory using GFP_NOWAIT, it would leak the reference to the file descriptor. Also the node pointed to by the xas could be freed between the call to xas_load() under the rcu_read_lock() and the acquisition of the xa_lock. It's easier to just use the normal xa_load/xa_store interface here. Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> [axboe: fix missing assign after alloc, cur_uring -> tctx rename] Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/io_uring.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -7929,27 +7929,24 @@ static void io_uring_cancel_task_request */ static int io_uring_add_task_file(struct file *file) { - if (unlikely(!current->io_uring)) { + struct io_uring_task *tctx = current->io_uring; + + if (unlikely(!tctx)) { int ret; ret = io_uring_alloc_task_context(current); if (unlikely(ret)) return ret; + tctx = current->io_uring; } - if (current->io_uring->last != file) { - XA_STATE(xas, ¤t->io_uring->xa, (unsigned long) file); - void *old; + if (tctx->last != file) { + void *old = xa_load(&tctx->xa, (unsigned long)file); - rcu_read_lock(); - old = xas_load(&xas); - if (old != file) { + if (!old) { get_file(file); - xas_lock(&xas); - xas_store(&xas, file); - xas_unlock(&xas); + xa_store(&tctx->xa, (unsigned long)file, file, GFP_KERNEL); } - rcu_read_unlock(); - current->io_uring->last = file; + tctx->last = file; } return 0; Patches currently in stable-queue which might be from willy@xxxxxxxxxxxxx are queue-5.8/io_uring-convert-advanced-xarray-uses-to-the-normal-api.patch queue-5.8/io_uring-fix-xarray-usage-in-io_uring_add_task_file.patch queue-5.8/io_uring-fix-use-of-xarray-in-__io_uring_files_cancel.patch