lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Tue, 03 Jul 2012 10:57:35 -0700
From:	Zach Brown <zab@...bo.net>
To:	Ric Wheeler <rwheeler@...hat.com>, Jan Kara <jack@...e.cz>,
	Eric Sandeen <sandeen@...hat.com>,
	Theodore Ts'o <tytso@....edu>, Fredrick <fjohnber@...o.com>,
	linux-ext4@...r.kernel.org, Andreas Dilger <adilger@...ger.ca>,
	wenqing.lz@...bao.com
Subject: Re: ext4_fallocate


> workload frequently does a uninitialized extent conversion.  Thus, now
> we set it to 256 (1MB chunk), and put it into super block in order to
> adjust it dynamically in sysfs.

It's a bit of a tangent, but this caught my eye.

> +	/* If extent has less than 2*s_extent_zeroout_len zerout directly */
> +	if (ee_len<= 2*sbi->s_extent_zeroout_len&&
>   	(EXT4_EXT_MAY_ZEROOUT&  split_flag)) {

> -		if (allocated<= EXT4_EXT_ZERO_LEN&&
> +		if (allocated<= sbi->s_extent_zeroout_len&&
>   		(EXT4_EXT_MAY_ZEROOUT&  split_flag)) {

>   		} else if ((map->m_lblk - ee_block + map->m_len<
> -			   EXT4_EXT_ZERO_LEN)&&
> +			   sbi->s_extent_zeroout_len)&&

I'd be worried about having to verify that nothing bad happened if these
sbi s_extent_zeroout_len references could see different values if they
raced with a sysfs update.  Can they do that?

Maybe avoid the risk all together and have an on-stack copy that's only
referenced once at the start?

- z
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists