linux-ext4 - Re: [PATCH v3] ext4: Fix reading of extended tv

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Message-ID: <20131108051757.GE11668@thunk.org>
Date:	Fri, 8 Nov 2013 00:17:57 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	David Turner <novalis@...alis.org>
Cc:	Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andreas Dilger <adilger.kernel@...ger.ca>
Subject: Re: [PATCH v3] ext4: Fix reading of extended tv_sec (bug 23732)

On Thu, Nov 07, 2013 at 06:26:47PM -0500, David Turner wrote:
> In ext4, the bottom two bits of {a,c,m}time_extra are used to extend
> the {a,c,m}time fields, deferring the year 2038 problem to the year
> 2446.  The representation (which this patch does not alter) is a bit
> hackish, in that the most-significant bit is no longer (alone)
> sufficient to indicate the sign.  That's because we're representing an
> asymmetric range, with seven times as many positive values as
> negative.
> 
> When decoding these extended fields, for times whose bottom 32 bits
> would represent a negative number, sign extension causes the 64-bit
> extended timestamp to be negative as well, which is not what's
> intended.  This patch corrects that issue, so that the only negative
> {a,c,m}times are those between 1901 and 1970 (as per 32-bit signed
> timestamps).
> 
> Signed-off-by: David Turner <novalis@...alis.org>
> Reported-by: Mark Harris <mh8928@...oo.com>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=23732
> Reviewed-by: Jan Kara <jack@...e.cz>

Thanks, applied.

					- Ted
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