On Tue, Jun 11, 2019 at 11:56:06PM +0000, Stephen Bates wrote: > The array_index_nospec() check in io_sq_offload_start() is performed > before any checks on p->sq_thread_cpu are done. This means cpu is > clamped and therefore no error occurs when out-of-range values are > passed in from userspace. This is in violation of the specification > for io_ring_setup() and causes the io_ring_setup unit test in liburing > to regress. > > Add a new bounds check on sq_thread_cpu at the start of > io_sq_offload_start() so we can exit the function early when bad > values are passed in. > > Fixes: 975554b03edd ("io_uring: fix SQPOLL cpu validation") > Signed-off-by: Stephen Bates <sbates@xxxxxxxxxxxx> Aargh. My original patch [1] handled that correctly, and this case was explicitly called out in the commit message, which was retained even when the patch was "simplified". That's rather disappointing. :/ Thanks, Mark. [1] https://lore.kernel.org/lkml/20190430123451.44227-1-mark.rutland@xxxxxxx/ > --- > fs/io_uring.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 30a5687..e458470 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -2316,6 +2316,9 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx, > { > int ret; > > + if (p->sq_thread_cpu >= nr_cpu_ids) > + return -EINVAL; > + > init_waitqueue_head(&ctx->sqo_wait); > mmgrab(current->mm); > ctx->sqo_mm = current->mm; > -- > 2.7.4 >