From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jia-Ju Bai <baijiaju1990@163.com>, Jan Kara <jack@suse.com>,
Sagi Grimberg <sagi@grimberg.me>,
james.smart@broadcom.com,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ext2/super: Fix a possible sleep-in-atomic bug in parse_options
Date: Sat, 7 Oct 2017 03:28:39 +0100 [thread overview]
Message-ID: <20171007022839.GP21978@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20171007020217.GN21978@ZenIV.linux.org.uk>
On Sat, Oct 07, 2017 at 03:02:17AM +0100, Al Viro wrote:
> > I do wonder if we shouldn't just use something like
> >
> > "skip leading zeroes, copy to size-limited stack location instead"
> >
> > because the input length really *is* limited once you skip leading
> > zeroes (and whatever base marker we have). We might have at most a
> > 64-bit value in octal, so 22 bytes max.
> >
> > But I guess just changing the two GFP_KERNEL's to GFP_ATOMIC is much simpler.
>
> There's match_strdup() as well...
>
> FWIW, ext2 side also looks fishy; it might be cleaner if we
> collected new state into some object and applied it only after the last
> possible failure exit. The entire "restore the original state" logics
> would go away...
I'm not saying that the bug had been introduced by conversion to
spinlock, BTW - it was racy back when ext2_remount() relied upon BKL.
I hadn't considered the atomicity issues back then - mea culpa...
next prev parent reply other threads:[~2017-10-07 2:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-07 1:20 [PATCH] ext2/super: Fix a possible sleep-in-atomic bug in parse_options Jia-Ju Bai
2017-10-07 1:37 ` Linus Torvalds
2017-10-07 1:55 ` Jia-Ju Bai
2017-10-07 2:02 ` Al Viro
2017-10-07 2:28 ` Al Viro [this message]
2017-10-09 13:32 ` Jan Kara
2017-10-08 22:20 ` Dave Chinner
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