From: Michel Lespinasse <walken@google.com>
To: Jann Horn <jannh@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Sakari Ailus <sakari.ailus@linux.intel.com>
Subject: Re: [PATCH 2/4] binfmt_elf: Take the mmap lock around find_extend_vma()
Date: Wed, 30 Sep 2020 16:22:00 -0700 [thread overview]
Message-ID: <CANN689HJoFxU+EhbtxEDXWngQqJzc-8LE0erWKVyLQ9wXuZK4w@mail.gmail.com> (raw)
In-Reply-To: <CAG48ez1-PBCdv3y8pn-Ty-b+FmBSLwDuVKFSt8h7wARLy0dF-Q@mail.gmail.com>
On Tue, Sep 29, 2020 at 6:20 PM Jann Horn <jannh@google.com> wrote:
> create_elf_tables() runs after setup_new_exec(), so other tasks can
> already access our new mm and do things like process_madvise() on it.
> (At the time I'm writing this commit, process_madvise() is not in mainline
> yet, but has been in akpm's tree for some time.)
>
> While I believe that there are currently no APIs that would actually allow
> another process to mess up our VMA tree (process_madvise() is limited to
> MADV_COLD and MADV_PAGEOUT, and uring and userfaultfd cannot reach an mm
> under which no syscalls have been executed yet), this seems like an
> accident waiting to happen.
>
> Let's make sure that we always take the mmap lock around GUP paths as long
> as another process might be able to see the mm.
>
> (Yes, this diff looks suspicious because we drop the lock before doing
> anything with `vma`, but that's because we actually don't do anything with
> it apart from the NULL check.)
>
> Signed-off-by: Jann Horn <jannh@google.com>
Thanks for these cleanups :)
Acked-by: Michel Lespinasse <walken@google.com>
next prev parent reply other threads:[~2020-09-30 23:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200930011944.19869-1-jannh@google.com>
2020-09-30 1:20 ` [PATCH 2/4] binfmt_elf: Take the mmap lock around find_extend_vma() Jann Horn
2020-09-30 23:22 ` Michel Lespinasse [this message]
2020-09-30 1:20 ` [PATCH 3/4] mmap locking API: Don't check locking if the mm isn't live yet Jann Horn
2020-09-30 12:30 ` Jason Gunthorpe
2020-09-30 12:50 ` Jann Horn
2020-09-30 20:14 ` Jann Horn
2020-09-30 23:26 ` Jason Gunthorpe
2020-09-30 23:51 ` Jann Horn
2020-10-01 19:15 ` Jason Gunthorpe
2020-10-01 20:16 ` Jann Horn
2020-10-01 23:41 ` Jason Gunthorpe
2020-10-01 23:55 ` Jann Horn
2020-09-30 23:42 ` Michel Lespinasse
2020-09-30 1:20 ` [PATCH 4/4] mm/gup: Assert that the mmap lock is held in __get_user_pages() Jann Horn
2020-09-30 12:32 ` Jason Gunthorpe
2020-09-30 23:24 ` Michel Lespinasse
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