From: Ryan Stone <rysto32@gmail.com>
To: linux-rdma@vger.kernel.org
Subject: Race condition between cm_migrate() and cm_remove_one()
Date: Wed, 4 Nov 2020 17:08:59 -0500 [thread overview]
Message-ID: <CAFMmRNx9cg--NUnZjFM8yWqFaEtsmAWV4EogKb3a0+hnjdtJFA@mail.gmail.com> (raw)
I believe that there is a serious bug in drivers/infiniband/core/cm.c
that can cause kernel memory corruption. The problem arises from the
interaction between cm_remove_one() and this code in cm_migrate():
https://code.woboq.org/linux/linux/drivers/infiniband/core/cm.c.html#3968
As I understand it, this code swaps the values of
prim_send_port_not_ready and altr_send_port_not_ready when we fail
over to the alternate path.
In cm_remove_one(), prim_send_port_not_ready and
altr_send_port_not_ready are set to true for every cm_id_priv
associated with the client being removed:
https://code.woboq.org/linux/linux/drivers/infiniband/core/cm.c.html#4478
I see two problems here: first, the two functions hold different
locks. This means that we can lose a write to
prim_send_port_not_ready or altr_send_port_not_ready if it happens
concurrently with cm_migrate().
Second, while we swap the values of prim_send_port_not_ready and
altr_send_port_not_ready, the associated cm_priv_prim_list and
cm_priv_altr_list lists are *not* swapped. I believe that either bug
can cause a subsequent call to cm_destroy_id() to write to the
cm_device that cm_remove_one() has already freed, potentially
corrupting kernel memory. The issue is the two list_del() calls here:
https://code.woboq.org/linux/linux/drivers/infiniband/core/cm.c.html#1103
If we lose the race with cm_migrate(), then then the list_del() call
can happen when it should not have. Alternatively, if cm_migrate()
has been invoked an odd number of times for the cm_id_priv and only
one of the prim port/altr port has been set to not ready, then
list_del() will be called on the wrong list.
I'm not very familiar with this code so I'm unsure of the best way to
fix it. One approach would be:
1) Hold cm.lock in cm_migrate() in addition to the cm_id_priv's lock, and
2) Also swap the contents of the two lists in cm_migrate()
If anybody could give input on my analysis and the proposed solution
I'd really appreciate it.
Thanks,
Ryan
next reply other threads:[~2020-11-04 22:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-04 22:08 Ryan Stone [this message]
2020-11-12 19:46 ` Race condition between cm_migrate() and cm_remove_one() Jason Gunthorpe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAFMmRNx9cg--NUnZjFM8yWqFaEtsmAWV4EogKb3a0+hnjdtJFA@mail.gmail.com \
--to=rysto32@gmail.com \
--cc=linux-rdma@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).