From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Tigran Aivazian <aivazian.tigran@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
syzbot <syzbot+71c6b5d68e91149fc8a4@syzkaller.appspotmail.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: [PATCH] bfs: add sanity check at bfs_fill_super().
Date: Thu, 14 Jun 2018 22:28:11 +0900 [thread overview]
Message-ID: <f8e7cc6b-78d0-a03d-3d6e-3fe685a7feea@i-love.sakura.ne.jp> (raw)
In-Reply-To: <CAK+_RLmxrdtxSxL-iVUfAgRAuSdC7hVV6QUZYxU5PDQUL-4nDg@mail.gmail.com>
On 2018/06/14 22:05, Tigran Aivazian wrote:
> On 14 June 2018 at 13:38, Dmitry Vyukov <dvyukov@google.com> wrote:
>> Consider, currently we can have a bfs image that works fine on one
>> kernel, but fails to mount on another just because it happens so that
>> one could allocate 4MB with kmalloc, but another can't (different
>> allocator/different settings/different kernel revision).
>
> Yes, but this would only happen _without_ the validation proposed by
> Tetsuo Handa. If we check s_start then the invalid enormous allocation
> request will not be made and what you describe won't not happen.
>
What is possible largest value for imap_len ?
info->si_lasti = (le32_to_cpu(bfs_sb->s_start) - BFS_BSIZE) / sizeof(struct bfs_inode) + BFS_ROOT_INO - 1;
imap_len = (info->si_lasti / 8) + 1;
info->si_imap = kzalloc(imap_len, GFP_KERNEL);
Since sizeof(struct bfs_inode) is 64 and bfs_sb->s_start is unsigned 32bits integer
(where constraints is BFS_BSIZE <= bfs_sb->s_start <= bfs_sb->s_end), theoretically
it is possible to assign bfs_sb->s_start > 2GB (apart from whether such value makes
sense). Then, isn't it possible that imap_len > 4M and still hit KMALLOC_MAX_SIZE limit?
next prev parent reply other threads:[~2018-06-14 13:28 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-09 10:35 [PATCH] bfs: add sanity check at bfs_fill_super() Tetsuo Handa
2018-05-09 23:06 ` Andrew Morton
[not found] ` <201805092346.w49NkINl045657@www262.sakura.ne.jp>
2018-05-09 23:53 ` Andrew Morton
2018-06-13 13:33 ` Tetsuo Handa
2018-06-13 13:49 ` Tigran Aivazian
2018-06-13 16:00 ` Dmitry Vyukov
2018-06-14 12:23 ` Tigran Aivazian
2018-06-14 12:38 ` Dmitry Vyukov
2018-06-14 13:05 ` Tigran Aivazian
2018-06-14 13:12 ` Dmitry Vyukov
2018-06-14 13:28 ` Tetsuo Handa [this message]
2018-06-14 15:13 ` Tigran Aivazian
2018-06-14 16:15 ` Tigran Aivazian
2018-06-14 19:00 ` Tigran Aivazian
2018-06-14 22:18 ` Tetsuo Handa
2018-06-15 10:45 ` Tigran Aivazian
2018-06-13 22:09 ` Tetsuo Handa
2018-06-14 7:38 ` Tigran Aivazian
2018-06-14 10:45 ` Tetsuo Handa
2018-06-14 12:11 ` Tigran Aivazian
2018-05-10 0:53 ` Matthew Wilcox
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