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Message-ID: <1e9159c8-48f5-cf1d-bc5a-e7e33ec0bf04@infradead.org>
Date: Fri, 23 Sep 2022 09:07:54 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
Andrew Morton <akpm@...ux-foundation.org>,
Namjae Jeon <linkinjeon@...nel.org>,
Shigeru Yoshida <syoshida@...hat.com>
Cc: syzbot <syzbot+1631f09646bc214d2e76@...kaller.appspotmail.com>,
syzkaller-bugs@...glegroups.com, ntfs3@...ts.linux.dev,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs/ntfs3: fix negative shift size in
true_sectors_per_clst()
Hi,
On 9/23/22 04:58, Konstantin Komarov wrote:
>
>
> On 9/23/22 03:38, Randy Dunlap wrote:
>> Hi,
>>
>> On 9/20/22 08:59, Tetsuo Handa wrote:
>>> syzbot is reporting shift-out-of-bounds in true_sectors_per_clst() [1], for
>>> commit a3b774342fa752a5 ("fs/ntfs3: validate BOOT sectors_per_clusters")
>>> did not address that (0 - boot->sectors_per_clusters) < 0 because "u8" was
>>> chosen for type of boot->sectors_per_clusters because 0x80 needs to be
>>> positive in order to support 64K clusters. Use "s8" cast in order to make
>>> sure that (0 - (s8) boot->sectors_per_clusters) > 0.
>>>
>>> Link: https://syzkaller.appspot.com/bug?extid=1631f09646bc214d2e76 [1]
>>> Reported-by: syzbot <syzbot+1631f09646bc214d2e76@...kaller.appspotmail.com>
>>> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
>>> Tested-by: syzbot <syzbot+1631f09646bc214d2e76@...kaller.appspotmail.com>
>>> Fixes: a3b774342fa752a5 ("fs/ntfs3: validate BOOT sectors_per_clusters")
>>>
>>> diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
>>> index 47012c9bf505..c7ffd21fb255 100644
>>> --- a/fs/ntfs3/super.c
>>> +++ b/fs/ntfs3/super.c
>>> @@ -672,7 +672,7 @@ static u32 true_sectors_per_clst(const struct NTFS_BOOT *boot)
>>> if (boot->sectors_per_clusters <= 0x80)
>>> return boot->sectors_per_clusters;
>>> if (boot->sectors_per_clusters >= 0xf4) /* limit shift to 2MB max */
>>> - return 1U << (0 - boot->sectors_per_clusters);
>>> + return 1U << (0 - (s8) boot->sectors_per_clusters);
>>> return -EINVAL;
>>> }
>>>
>>
>> I slightly prefer the earlier patch:
>>
>> https://lore.kernel.org/all/20220823144625.1627736-1-syoshida@redhat.com/
>>
>> but it appears that the NTFS3 maintainer is MIA again. :(
>>
>
> Hello
>
> I've sent patches on 12.09, so I'm not MIA.
> I plan to look at patches next week, there are quite a lot of them.
OK, good news. Thanks.
--
~Randy
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