[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <631a1251-5bbc-484d-9bd9-167c5e7cb69f@linux.dev>
Date: Thu, 31 Jul 2025 22:19:57 +0200
From: Bernard Metzler <bernard.metzler@...ux.dev>
To: Pedro Falcato <pfalcato@...e.de>
Cc: Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>,
Vlastimil Babka <vbabka@...e.cz>, Jakub Kicinski <kuba@...nel.org>,
David Howells <dhowells@...hat.com>, Tom Talpey <tom@...pey.com>,
linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, torvalds@...ux-foundation.org, stable@...r.kernel.org,
kernel test robot <oliver.sang@...el.com>
Subject: Re: [PATCH v2] RDMA/siw: Fix the sendmsg byte count in
siw_tcp_sendpages
On 30.07.2025 11:26, Pedro Falcato wrote:
> On Tue, Jul 29, 2025 at 08:53:02PM +0200, Bernard Metzler wrote:
>> On 29.07.2025 14:03, Pedro Falcato wrote:
>>> Ever since commit c2ff29e99a76 ("siw: Inline do_tcp_sendpages()"),
>>> we have been doing this:
>>>
>>> static int siw_tcp_sendpages(struct socket *s, struct page **page, int offset,
>>> size_t size)
>>> [...]
>>> /* Calculate the number of bytes we need to push, for this page
>>> * specifically */
>>> size_t bytes = min_t(size_t, PAGE_SIZE - offset, size);
>>> /* If we can't splice it, then copy it in, as normal */
>>> if (!sendpage_ok(page[i]))
>>> msg.msg_flags &= ~MSG_SPLICE_PAGES;
>>> /* Set the bvec pointing to the page, with len $bytes */
>>> bvec_set_page(&bvec, page[i], bytes, offset);
>>> /* Set the iter to $size, aka the size of the whole sendpages (!!!) */
>>> iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
>>> try_page_again:
>>> lock_sock(sk);
>>> /* Sendmsg with $size size (!!!) */
>>> rv = tcp_sendmsg_locked(sk, &msg, size);
>>>
>>> This means we've been sending oversized iov_iters and tcp_sendmsg calls
>>> for a while. This has a been a benign bug because sendpage_ok() always
>>> returned true. With the recent slab allocator changes being slowly
>>> introduced into next (that disallow sendpage on large kmalloc
>>> allocations), we have recently hit out-of-bounds crashes, due to slight
>>> differences in iov_iter behavior between the MSG_SPLICE_PAGES and
>>> "regular" copy paths:
>>>
>>> (MSG_SPLICE_PAGES)
>>> skb_splice_from_iter
>>> iov_iter_extract_pages
>>> iov_iter_extract_bvec_pages
>>> uses i->nr_segs to correctly stop in its tracks before OoB'ing everywhere
>>> skb_splice_from_iter gets a "short" read
>>>
>>> (!MSG_SPLICE_PAGES)
>>> skb_copy_to_page_nocache copy=iov_iter_count
>>> [...]
>>> copy_from_iter
>>> /* this doesn't help */
>>> if (unlikely(iter->count < len))
>>> len = iter->count;
>>> iterate_bvec
>>> ... and we run off the bvecs
>>>
>>> Fix this by properly setting the iov_iter's byte count, plus sending the
>>> correct byte count to tcp_sendmsg_locked.
>>>
>>> Cc: stable@...r.kernel.org
>>> Fixes: c2ff29e99a76 ("siw: Inline do_tcp_sendpages()")
>>> Reported-by: kernel test robot <oliver.sang@...el.com>
>>> Closes: https://lore.kernel.org/oe-lkp/202507220801.50a7210-lkp@intel.com
>>> Reviewed-by: David Howells <dhowells@...hat.com>
>>> Signed-off-by: Pedro Falcato <pfalcato@...e.de>
>>> ---
>>>
>>> v2:
>>> - Add David Howells's Rb on the original patch
>>> - Remove the offset increment, since it's dead code
>>>
>>> drivers/infiniband/sw/siw/siw_qp_tx.c | 5 ++---
>>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/infiniband/sw/siw/siw_qp_tx.c b/drivers/infiniband/sw/siw/siw_qp_tx.c
>>> index 3a08f57d2211..f7dd32c6e5ba 100644
>>> --- a/drivers/infiniband/sw/siw/siw_qp_tx.c
>>> +++ b/drivers/infiniband/sw/siw/siw_qp_tx.c
>>> @@ -340,18 +340,17 @@ static int siw_tcp_sendpages(struct socket *s, struct page **page, int offset,
>>> if (!sendpage_ok(page[i]))
>>> msg.msg_flags &= ~MSG_SPLICE_PAGES;
>>> bvec_set_page(&bvec, page[i], bytes, offset);
>>> - iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
>>> + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, bytes);
>>> try_page_again:
>>> lock_sock(sk);
>>> - rv = tcp_sendmsg_locked(sk, &msg, size);
>>> + rv = tcp_sendmsg_locked(sk, &msg, bytes)
>>> release_sock(sk);
>>> if (rv > 0) {
>>> size -= rv;
>>> sent += rv;
>>> if (rv != bytes) {
>>> - offset += rv;
>>> bytes -= rv;
>>> goto try_page_again;
>>> }
>> Acked-by: Bernard Metzler <bernard.metzler@...ux.dev>
>
> Thanks!
>
> Do you want to take the fix through your tree? Otherwise I suspect Vlastimil
> could simply take it (and possibly resubmit the SLAB PR, which hasn't been
> merged yet).
>
Thanks Pedro. Having Vlastimil taking care sounds good to me.
I am currently without development infrastructure (small village
in the mountains thing). And fixing the SLAB PR in the
first place would be even better.
Best,
Bernard.
Powered by blists - more mailing lists