From: Matthew Wilcox <willy@infradead.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: syzbot <syzbot+96cee7d33ca3f87eee86@syzkaller.appspotmail.com>,
ntfs3@lists.linux.dev, syzkaller-bugs@googlegroups.com,
Konstantin Komarov <almaz.alexandrovich@paragon-software.com>,
Hillf Danton <hdanton@sina.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
trix@redhat.com, ndesaulniers@google.com, nathan@kernel.org
Subject: Re: [PATCH] fs/ntfs3: disable page fault during ntfs_fiemap()
Date: Wed, 12 Apr 2023 14:13:48 +0100 [thread overview]
Message-ID: <ZDaujCO3Azv92JxX@casper.infradead.org> (raw)
In-Reply-To: <f649c9c0-6c0c-dd0d-e3c9-f0c580a11cd9@I-love.SAKURA.ne.jp>
On Wed, Apr 12, 2023 at 10:11:08PM +0900, Tetsuo Handa wrote:
> syzbot is reporting circular locking dependency between ntfs_file_mmap()
> (which has mm->mmap_lock => ni->ni_lock dependency) and ntfs_fiemap()
> (which has ni->ni_lock => mm->mmap_lock dependency).
>
> Since ni_fiemap() is called by ioctl(FS_IOC_FIEMAP) via optional
> "struct inode_operations"->fiemap callback, I assume that importance of
> ni_fiemap() is lower than ntfs_file_mmap().
>
> Also, since Documentation/filesystems/fiemap.rst says that "If an error
> is encountered while copying the extent to user memory, -EFAULT will be
> returned.", I assume that ioctl(FS_IOC_FIEMAP) users can handle -EFAULT
> error.
What? No, that doesn't mean "You can return -EFAULT because random luck".
That means "If you pass it an invalid address, you'll get -EFAULT back".
NACK.
next prev parent reply other threads:[~2023-04-12 13:14 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-30 12:51 [syzbot] possible deadlock in ntfs_fiemap syzbot
2022-12-09 4:00 ` syzbot
2023-04-12 13:11 ` [PATCH] fs/ntfs3: disable page fault during ntfs_fiemap() Tetsuo Handa
2023-04-12 13:13 ` Matthew Wilcox [this message]
2023-04-12 13:29 ` Tetsuo Handa
2023-04-12 14:24 ` Matthew Wilcox
2023-04-17 14:03 ` [PATCH] vfs: allow using kernel buffer during fiemap operation Tetsuo Handa
2023-04-20 21:00 ` Al Viro
2023-04-20 21:11 ` Al Viro
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