On 7/19/19 10:03 AM, Eric Blake wrote: > We've had two separate reports of a caller running into use of > uninitialized data if s->quit is set (one detected by gcc -O3, another > by valgrind), due to checking 'nbd_reply_is_simple(reply) || s->quit' > in the wrong order. Rather than chasing down which callers need to > pre-initialize reply, it's easier to guarantee that reply will always > be set by nbd_co_receive_one_chunk() even on failure. > > Reported-by: Thomas Huth <th...@redhat.com> > Reported-by: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com> > Signed-off-by: Eric Blake <ebl...@redhat.com> > --- >
Blech. Needs a v2. Expanding context: > +++ b/block/nbd.c > @@ -640,6 +640,7 @@ static coroutine_fn int nbd_co_receive_one_chunk( > request_ret, qiov, payload, errp); > > if (ret < 0) { > + memset(reply, 0, sizeof *reply); > s->quit = true; > } else { > /* For assert at loop start in nbd_connection_entry */ if (reply) { *reply = s->reply; } either callers can pass in reply==NULL (in which case the memset() dereferences NULL, oops), or always pass in non-NULL reply (in which case the null check is dead code). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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