From: Matthew Wilcox <willy@infradead.org>
To: syzbot <syzbot+da4fe66aaadd3c2e2d1c@syzkaller.appspotmail.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
namjae.jeon@samsung.com, sj1557.seo@samsung.com,
syzkaller-bugs@googlegroups.com
Subject: Re: UBSAN: shift-out-of-bounds in exfat_fill_super
Date: Mon, 25 Jan 2021 18:39:18 +0000 [thread overview]
Message-ID: <20210125183918.GH308988@casper.infradead.org> (raw)
In-Reply-To: <000000000000c2865c05b9bcee02@google.com>
On Mon, Jan 25, 2021 at 09:33:14AM -0800, syzbot wrote:
> UBSAN: shift-out-of-bounds in fs/exfat/super.c:471:28
> shift exponent 4294967294 is too large for 32-bit type 'int'
This is an integer underflow:
sbi->dentries_per_clu = 1 <<
(sbi->cluster_size_bits - DENTRY_SIZE_BITS);
I think the problem is that there is no validation of sect_per_clus_bits.
We should check it is at least DENTRY_SIZE_BITS and probably that it's
less than ... 16? 64? I don't know what legitimate values are in this
field, but I would imagine that 255 is completely unacceptable.
next prev parent reply other threads:[~2021-01-25 18:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-25 17:33 UBSAN: shift-out-of-bounds in exfat_fill_super syzbot
2021-01-25 18:39 ` Matthew Wilcox [this message]
2021-01-26 4:33 ` Randy Dunlap
2021-01-26 5:14 ` Namjae Jeon
2021-01-26 4:40 ` Namjae Jeon
2021-01-26 5:08 ` Namjae Jeon
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