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From: James Smart <james.smart@broadcom.com>
To: Kees Cook <keescook@chromium.org>, Willy Tarreau <w@1wt.eu>
Cc: Silvio Cesare <silvio.cesare@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Dick Kennedy <dick.kennedy@broadcom.com>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Will Deacon <will.deacon@arm.com>, Greg KH <greg@kroah.com>
Subject: Re: [PATCH 5/8] scsi: lpfc: change snprintf to scnprintf for possible overflow
Date: Tue, 15 Jan 2019 14:41:17 -0800	[thread overview]
Message-ID: <de134f7c-7516-cfb4-7cd2-6d96b45bdb48@broadcom.com> (raw)
In-Reply-To: <CAGXu5jKu5br-pB3U+3PDtgcgq_nmt0C7gHLYQXV4tz3pN=S11Q@mail.gmail.com>


On 1/14/2019 5:15 PM, Kees Cook wrote:
> On Sat, Jan 12, 2019 at 7:29 AM Willy Tarreau<w@1wt.eu>  wrote:
>> From: Silvio Cesare<silvio.cesare@gmail.com>
>>
>> Change snprintf to scnprintf. There are generally two cases where using
>> snprintf causes problems.
>>
>> 1) Uses of size += snprintf(buf, SIZE - size, fmt, ...)
>> In this case, if snprintf would have written more characters than what the
>> buffer size (SIZE) is, then size will end up larger than SIZE. In later
>> uses of snprintf, SIZE - size will result in a negative number, leading
>> to problems. Note that size might already be too large by using
>> size = snprintf before the code reaches a case of size += snprintf.
>>
>> 2) If size is ultimately used as a length parameter for a copy back to user
>> space, then it will potentially allow for a buffer overflow and information
>> disclosure when size is greater than SIZE. When the size is used to index
>> the buffer directly, we can have memory corruption. This also means when
>> size = snprintf... is used, it may also cause problems since size may become
>> large.  Copying to userspace is mitigated by the HARDENED_USERCOPY kernel
>> configuration.
>>
>> The solution to these issues is to use scnprintf which returns the number of
>> characters actually written to the buffer, so the size variable will never
>> exceed SIZE.
>>
>> Signed-off-by: Silvio Cesare<silvio.cesare@gmail.com>
>> Cc: James Smart<james.smart@broadcom.com>
>> Cc: Dick Kennedy<dick.kennedy@broadcom.com>
>> Cc: Dan Carpenter<dan.carpenter@oracle.com>
>> Cc: Kees Cook<keescook@chromium.org>
>> Cc: Will Deacon<will.deacon@arm.com>
>> Cc: Greg KH<greg@kroah.com>
>> Signed-off-by: Willy Tarreau<w@1wt.eu>
> I think this needs Cc: stable.
>
> Reviewed-by: Kees Cook<keescook@chromium.org>
>
> -Kees
>


Reviewed-by:  James Smart <james.smart@broadcom.com>

-- james


  reply	other threads:[~2019-01-15 22:41 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-12 15:28 [PATCH 1/8] lkdtm: change snprintf to scnprintf for possible overflow Willy Tarreau
2019-01-12 15:28 ` [PATCH 2/8] libertas: " Willy Tarreau
2019-01-15  1:09   ` Kees Cook
2019-01-15  5:55   ` Kalle Valo
2019-01-15 20:35     ` Willy Tarreau
2019-01-16 16:40       ` Kalle Valo
2019-01-16 17:02         ` Willy Tarreau
2019-01-12 15:28 ` [PATCH 3/8] ocfs2: " Willy Tarreau
2019-01-15  1:14   ` Kees Cook
2019-01-12 15:28 ` [PATCH 4/8] ASoC: " Willy Tarreau
2019-01-15  1:13   ` Kees Cook
2019-01-15  1:25   ` Nicolin Chen
2019-01-15  3:18     ` Willy Tarreau
2019-01-12 15:28 ` [PATCH 5/8] scsi: lpfc: " Willy Tarreau
2019-01-15  1:15   ` Kees Cook
2019-01-15 22:41     ` James Smart [this message]
2019-03-20 17:39       ` Greg KH
2019-03-20 20:27         ` James Smart
2019-03-21  0:41         ` James Smart
2019-01-12 15:28 ` [PATCH 6/8] ASoC: intel: skylake: " Willy Tarreau
2019-01-15  1:12   ` Kees Cook
2019-01-16 18:41   ` Kees Cook
2019-01-16 19:35     ` Pierre-Louis Bossart
2019-01-16 19:51       ` Kees Cook
2019-01-12 15:28 ` [PATCH 7/8] ASoC: dapm: " Willy Tarreau
2019-01-14 14:56   ` Mark Brown
2019-01-15  3:16     ` Willy Tarreau
2019-01-15 15:44       ` Mark Brown
2019-01-15 15:55         ` Willy Tarreau
2019-01-12 15:28 ` [PATCH 8/8] spi: dw: " Willy Tarreau
2019-01-15  1:09   ` Kees Cook
2019-01-15  1:02 ` [PATCH 1/8] lkdtm: " Kees Cook
2019-01-15  1:07   ` Kees Cook
2019-01-15  3:12   ` Willy Tarreau
2019-01-15 20:47 ` Kees Cook
2019-01-18 13:06   ` Greg KH

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