linux-kernel - Re: [PATCH] smbfs: Read buffer overflow

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Message-Id: <20090724164909.b3f6cf2b.akpm@linux-foundation.org>
Date:	Fri, 24 Jul 2009 16:49:09 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Roel Kluin <roel.kluin@...il.com>
Cc:	linux-kernel@...r.kernel.org, Zhaolei <zhaolei@...fujitsu.com>
Subject: Re: [PATCH] smbfs: Read buffer overflow

On Thu, 23 Jul 2009 17:48:49 +0200
Roel Kluin <roel.kluin@...il.com> wrote:

> This function uses signed integers for the unix_date and local variables - if a
> negative number is supplied and the leap-year condition is not met, month
> will be 0, leading to a read of day_n[-1]
> 
> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
> This is the easiest way to prevent the buffer overflow, but it produces a date.
> Maybe a magic date would be better? What should we choose?
> 
> Credits to Parfait and Nathan Keynes,
> 
> diff --git a/fs/smbfs/proc.c b/fs/smbfs/proc.c
> index 9468168..71c29b6 100644
> --- a/fs/smbfs/proc.c
> +++ b/fs/smbfs/proc.c
> @@ -509,7 +509,7 @@ date_unix2dos(struct smb_sb_info *server,
>  		month = 2;
>  	} else {
>  		nl_day = (year & 3) || day <= 59 ? day : day - 1;
> -		for (month = 0; month < 12; month++)
> +		for (month = 1; month < 12; month++)
>  			if (day_n[month] > nl_day)
>  				break;
>  	}

Again, fixable by switching to the kernel/time/timeconv.c functions.
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