From: Dylan Yudaken <dylany@xxxxxx> commit 80912cef18f16f8fe59d1fb9548d4364342be360 upstream. io_rsrc_ref_quiesce will unlock the uring while it waits for references to the io_rsrc_data to be killed. There are other places to the data that might add references to data via calls to io_rsrc_node_switch. There is a race condition where this reference can be added after the completion has been signalled. At this point the io_rsrc_ref_quiesce call will wake up and relock the uring, assuming the data is unused and can be freed - although it is actually being used. To fix this check in io_rsrc_ref_quiesce if a resource has been revived. Reported-by: syzbot+ca8bf833622a1662745b@xxxxxxxxxxxxxxxxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Dylan Yudaken <dylany@xxxxxx> Link: https://lore.kernel.org/r/20220222161751.995746-1-dylany@xxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/io_uring.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -7818,7 +7818,15 @@ static int io_rsrc_ref_quiesce(struct io ret = wait_for_completion_interruptible(&data->done); if (!ret) { mutex_lock(&ctx->uring_lock); - break; + if (atomic_read(&data->refs) > 0) { + /* + * it has been revived by another thread while + * we were unlocked + */ + mutex_unlock(&ctx->uring_lock); + } else { + break; + } } atomic_inc(&data->refs);
