From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xin Long Subject: Re: [PATCHv2 net] sctp: check and update stream->out_curr when allocating stream_out Date: Fri, 30 Nov 2018 15:22:39 +0900 Message-ID: References: <8a5df8eb5cc41dfc3d08e294147b9729bbe90aa0.1543473776.git.lucien.xin@gmail.com> <20181129143855.GB14550@hmswarspite.think-freely.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: network dev , linux-sctp@vger.kernel.org, davem , Marcelo Ricardo Leitner To: Neil Horman Return-path: Received: from mail-io1-f67.google.com ([209.85.166.67]:39359 "EHLO mail-io1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726355AbeK3RbE (ORCPT ); Fri, 30 Nov 2018 12:31:04 -0500 In-Reply-To: <20181129143855.GB14550@hmswarspite.think-freely.org> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Nov 29, 2018 at 11:39 PM Neil Horman wrote: > > On Thu, Nov 29, 2018 at 02:42:56PM +0800, Xin Long wrote: > > Now when using stream reconfig to add out streams, stream->out > > will get re-allocated, and all old streams' information will > > be copied to the new ones and the old ones will be freed. > > > > So without stream->out_curr updated, next time when trying to > > send from stream->out_curr stream, a panic would be caused. > > > > This patch is to check and update stream->out_curr when > > allocating stream_out. > > > > v1->v2: > > - define fa_index() to get elem index from stream->out_curr. > > > > Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations") > > Reported-by: Ying Xu > > Reported-by: syzbot+e33a3a138267ca119c7d@syzkaller.appspotmail.com > > Signed-off-by: Xin Long > > --- > > net/sctp/stream.c | 20 ++++++++++++++++++++ > > 1 file changed, 20 insertions(+) > > > > diff --git a/net/sctp/stream.c b/net/sctp/stream.c > > index 3892e76..30e7809 100644 > > --- a/net/sctp/stream.c > > +++ b/net/sctp/stream.c > > @@ -84,6 +84,19 @@ static void fa_zero(struct flex_array *fa, size_t index, size_t count) > > } > > } > > > > +static size_t fa_index(struct flex_array *fa, void *elem, size_t count) > > +{ > > + size_t index = 0; > > + > > + while (count--) { > > + if (elem == flex_array_get(fa, index)) > > + break; > > + index++; > > + } > > + > > + return index; > > +} > > + > > /* Migrates chunks from stream queues to new stream queues if needed, > > * but not across associations. Also, removes those chunks to streams > > * higher than the new max. > > @@ -147,6 +160,13 @@ static int sctp_stream_alloc_out(struct sctp_stream *stream, __u16 outcnt, > > > > if (stream->out) { > > fa_copy(out, stream->out, 0, min(outcnt, stream->outcnt)); > > + if (stream->out_curr) { > > + size_t index = fa_index(stream->out, stream->out_curr, > > + stream->outcnt); > > + > > + BUG_ON(index == stream->outcnt); > > + stream->out_curr = flex_array_get(out, index); > > + } > > fa_free(stream->out); > > } > > > > -- > > 2.1.0 > > > > > > This is the sort of thing I'm talking about. Its a little more code, but if you > augment the flex_array api like this, you can preform a resize operation on your > existing flex array, and you can avoid all the copying, and need to update > pointers maintained outside the array. Note this code isn't tested at all, but > its close to what I think should work. > > > diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h > index b94fa61b51fb..7fa1f27a91b5 100644 > --- a/include/linux/flex_array.h > +++ b/include/linux/flex_array.h > @@ -73,6 +73,8 @@ struct flex_array { > struct flex_array *flex_array_alloc(int element_size, unsigned int total, > gfp_t flags); > > +struct flex_array *flex_array_resize(struct flex_array *fa, unsigned int total, gfp_t flags); > + > /** > * flex_array_prealloc() - Ensures that memory for the elements indexed in the > * range defined by start and nr_elements has been allocated. > diff --git a/lib/flex_array.c b/lib/flex_array.c > index 2eed22fa507c..f8d54af3891b 100644 > --- a/lib/flex_array.c > +++ b/lib/flex_array.c > @@ -109,6 +109,7 @@ struct flex_array *flex_array_alloc(int element_size, unsigned int total, > ret->total_nr_elements = total; > ret->elems_per_part = elems_per_part; > ret->reciprocal_elems = reciprocal_elems; > + ret->elements_used = 0; > if (elements_fit_in_base(ret) && !(flags & __GFP_ZERO)) > memset(&ret->parts[0], FLEX_ARRAY_FREE, > FLEX_ARRAY_BASE_BYTES_LEFT); > @@ -116,6 +117,53 @@ struct flex_array *flex_array_alloc(int element_size, unsigned int total, > } > EXPORT_SYMBOL(flex_array_alloc); > > +static int flex_array_last_element_index(struct flex_array *fa) > +{ > + struct flex_array_part *part; > + int part_nr; > + int i,j; > + > + if (elements_fit_in_base(fa)) { > + part = (struct flex_array_part *)&fa->parts[0]; > + for (i = fa->elems_per_part; i >= 0; i--) > + if (part->elements[i] != FLEX_ARRAY_FREE) > + return i; > + } > + > + i = fa->total_nr_elements; > + for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) { > + part = fa->parts[part_nr]; > + if (!part) { > + i -= fa->elems_per_part; > + continue; > + } > + for (j = fa->elems_per_part; j >= 0; j--, i--) > + if (part->elements[j] != FLEX_ARRAY_FREE) > + goto out; > + } > +out: > + return i; > +} > + > +struct flex_array *flex_array_resize(struct flex_array *fa, unsigned int total, gfp_t flags) > +{ > + if (total >= fa->total_nr_elements) { > + /* Grow case */ > + if (total > max_size) > + return ERR_PTR(-ETOOBIG); > + fa->total_nr_elements = total; > + } else { > + /* Shrink case */ > + /* Drop any pages we don't need*/ > + flex_array_shrink(fa); > + if (flex_array_last_element_index(fa) >= total) > + return ERR_PTR(-ESIZE); > + fa->total_nr_elements = total; > + } > + return fa; > +} > +EXPORT_SYMBOL(flex_array_resize); > + > static int fa_element_to_part_nr(struct flex_array *fa, > unsigned int element_nr) > { I have a question about how it checks one part is free in flex_array_shrink(): part_is_free() is doing it by checking: if (part->elements[all] == FLEX_ARRAY_FREE) ... What if the data in the array that users put is FLEX_ARRAY_FREE, it will be treated as free, but in fact it's still in use?