From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758815Ab3KMIUB (ORCPT ); Wed, 13 Nov 2013 03:20:01 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:37568 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758265Ab3KMITw (ORCPT ); Wed, 13 Nov 2013 03:19:52 -0500 Date: Wed, 13 Nov 2013 00:19:40 -0800 From: "Darrick J. Wong" To: David Turner Cc: Andreas Dilger , "Theodore Ts'o" , Mark Harris , Jan Kara , Ext4 Developers List , Linux Kernel Mailing List Subject: Re: [PATCH v4 1/2] ext4: Fix handling of extended tv_sec (bug 23732) Message-ID: <20131113081940.GB10269@birch.djwong.org> References: <1383864864.23882.33.camel@chiang> <20131107231445.GG2054@quack.suse.cz> <1383866807.23882.41.camel@chiang> <1383981551.8994.27.camel@chiang> <1384070214.8994.47.camel@chiang> <20131112003018.GA30281@thunk.org> <6DE0AF86-98E6-4DE9-BB7F-40FB32E1BC26@dilger.ca> <1384326015.8994.185.camel@chiang> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1384326015.8994.185.camel@chiang> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 13, 2013 at 02:00:15AM -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. > > 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). > > Some older kernels might have written pre-1970 dates with 1,1 in the > extra bits. This patch treats those incorrectly-encoded dates as > pre-1970, instead of post-2311, until kernel 4.20 is released. > Hopefully by then e2fsck will have fixed up the bad data. > > Signed-off-by: David Turner > Reported-by: Mark Harris > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=23732 > --- > fs/ext4/ext4.h | 61 +++++++++++++++++++++++++++++++++++++--------------------- > 1 file changed, 39 insertions(+), 22 deletions(-) > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > index 18aa56b..7d5e019 100644 > --- a/fs/ext4/ext4.h > +++ b/fs/ext4/ext4.h > @@ -26,6 +26,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -713,38 +714,54 @@ struct move_extent { > sizeof((ext4_inode)->field)) \ > <= (EXT4_GOOD_OLD_INODE_SIZE + \ > (einode)->i_extra_isize)) \ > + > /* > - * We use the bottom 34 bits of the signed 64-bit time value, with > - * the top two of these bits in the bottom of extra. This leads > - * to a slightly odd encoding, which works like this: > + * We need is an encoding that preserves the times for extra epoch "00": > * > - * extra msb of > - * epoch 32-bit > - * bits time decoded 64-bit tv_sec valid time range > - * 0 0 0 0x000000000..0x07fffffff 1970-01-01..2038-01-19 > - * 0 0 1 0x080000000..0x0ffffffff 2038-01-19..2106-02-07 > - * 0 1 0 0x100000000..0x17fffffff 2106-02-07..2174-02-25 > - * 0 1 1 0x180000000..0x1ffffffff 2174-02-25..2242-03-16 > - * 1 0 0 0x200000000..0x27fffffff 2242-03-16..2310-04-04 > - * 1 0 1 0x280000000..0x2ffffffff 2310-04-04..2378-04-22 > - * 1 1 0 0x300000000..0x37fffffff 2378-04-22..2446-05-10 > - > - * 1 1 1 -0x80000000..-0x00000001 1901-12-13..1969-12-31 > + * extra msb of adjust for signed > + * epoch 32-bit 32-bit tv_sec to > + * bits time decoded 64-bit tv_sec 64-bit tv_sec valid time range > + * 0 0 1 -0x80000000..-0x00000001 0x000000000 1901-12-13..1969-12-31 > + * 0 0 0 0x000000000..0x07fffffff 0x000000000 1970-01-01..2038-01-19 > + * 0 1 1 0x080000000..0x0ffffffff 0x100000000 2038-01-19..2106-02-07 > + * 0 1 0 0x100000000..0x17fffffff 0x100000000 2106-02-07..2174-02-25 > + * 1 0 1 0x180000000..0x1ffffffff 0x200000000 2174-02-25..2242-03-16 > + * 1 0 0 0x200000000..0x27fffffff 0x200000000 2242-03-16..2310-04-04 > + * 1 1 1 0x280000000..0x2ffffffff 0x300000000 2310-04-04..2378-04-22 > + * 1 1 0 0x300000000..0x37fffffff 0x300000000 2378-04-22..2446-05-10 > + * > + * Note that previous versions of the kernel on 64-bit systems would > + * incorrectly use extra epoch bits 1,1 for dates between 1901 and > + * 1970. e2fsck will correct this, assuming that it is run on the > + * affected filesystem before 2311. Given the table, should this be "before 2310-04-04"? --D > */ > > static inline __le32 ext4_encode_extra_time(struct timespec *time) > { > - return cpu_to_le32((sizeof(time->tv_sec) > 4 ? > - (time->tv_sec >> 32) & EXT4_EPOCH_MASK : 0) | > - ((time->tv_nsec << EXT4_EPOCH_BITS) & EXT4_NSEC_MASK)); > + u32 extra = sizeof(time->tv_sec) > 4 ? > + ((time->tv_sec - (s32)time->tv_sec) >> 32) & EXT4_EPOCH_MASK : 0; > + return cpu_to_le32(extra | (time->tv_nsec << EXT4_EPOCH_BITS)); > } > > static inline void ext4_decode_extra_time(struct timespec *time, __le32 extra) > { > - if (sizeof(time->tv_sec) > 4) > - time->tv_sec |= (__u64)(le32_to_cpu(extra) & EXT4_EPOCH_MASK) > - << 32; > - time->tv_nsec = (le32_to_cpu(extra) & EXT4_NSEC_MASK) >> EXT4_EPOCH_BITS; > + if (unlikely(sizeof(time->tv_sec) > 4 && > + (extra & cpu_to_le32(EXT4_EPOCH_MASK)))) { > +#if LINUX_VERSION_CODE < KERNEL_VERSION(4,20,0) > + /* Handle legacy encoding of pre-1970 dates with epoch > + * bits 1,1. We assume that by kernel version 4.20, > + * everyone will have run fsck over the affected > + * filesystems to correct the problem. > + */ > + u64 extra_bits = le32_to_cpu(extra) & EXT4_EPOCH_MASK; > + if (extra_bits == 3) > + extra_bits = 0; > + time->tv_sec += extra_bits << 32; > +#else > + time->tv_sec += (u64)(le32_to_cpu(extra) & EXT4_EPOCH_MASK) << 32; > +#endif > + } > + time->tv_nsec = (le32_to_cpu(extra) & EXT4_NSEC_MASK) >> EXT4_EPOCH_BITS; > } > > #define EXT4_INODE_SET_XTIME(xtime, inode, raw_inode) \ > -- > 1.8.1.2 > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html