linux-ext4 - Re: [PATCH] fs: ext4: Sign-extend tv

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Date:	Mon, 31 Mar 2014 08:42:06 -0700
From:	Conrad Meyer <cse.cem@...il.com>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	Conrad Meyer <cemeyer@...edu>, "Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs: ext4: Sign-extend tv_sec after ORing in epoch bits

The problem exists in mainline (v3.14) and linux-next (20140328), so
it looks like it didn't land. Unless it's queued in an ext4 tree and
didn't get selected for Linus for some reason?

Thanks,
Conrad

On Mon, Mar 31, 2014 at 8:34 AM, Andreas Dilger <adilger@...ger.ca> wrote:
> Hmm,
> I thought there was a separate patch to fix this a few months ago, that was "more correct" than this one?  Did that not land?
>
> Cheers, Andreas
>
>> On Mar 30, 2014, at 8:58, Conrad Meyer <cemeyer@...edu> wrote:
>>
>> Fixes kernel.org bug #23732.
>>
>> Background: ext4 stores time as a 34-bit quantity; 2 bits in some extra
>> bits unneeded for nanoseconds in the inode, and 32 bits in the seconds
>> field.
>>
>> On systems with 64-bit time_t, the EXT4_*INODE_GET_XTIME() code
>> incorrectly sign-extended the low 32-bits of the seconds quantity before
>> ORing in the 2 "epoch" bits from nanoseconds.
>>
>> This patch ORs in the 2 higher bits, then sign extends the 34-bit signed
>> number to 64 bits.
>>
>> Signed-off-by: Conrad Meyer <cse.cem@...il.com>
>> ---
>> Patch against next-20140328.
>>
>> Note, the on-disk format has always been written correctly. It was just
>> interpreted incorrectly.
>>
>> Repro:
>> Before:
>> $ touch -d 2038-01-31 test-123
>> $ sudo sh -c "echo 3 > /proc/sys/vm/drop_caches"
>> $ ls -ld test-123
>> drwxrwxr-x 2 cmeyer cmeyer 4096 Dec 25  1901 test-123
>>
>> After:
>> $ ls -ld test-123
>> drwxrwxr-x 2 cmeyer cmeyer 4096 Jan 31  2038 test-123
>>
>> Thanks!
>> ---
>> fs/ext4/ext4.h | 14 ++++++++++++--
>> 1 file changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> index f4f889e..07ee03d 100644
>> --- a/fs/ext4/ext4.h
>> +++ b/fs/ext4/ext4.h
>> @@ -710,6 +710,8 @@ struct move_extent {
>> #define EXT4_EPOCH_BITS 2
>> #define EXT4_EPOCH_MASK ((1 << EXT4_EPOCH_BITS) - 1)
>> #define EXT4_NSEC_MASK  (~0UL << EXT4_EPOCH_BITS)
>> +#define EXT4_EPOCH_SIGN (((1UL << (EXT4_EPOCH_BITS - 1)) << 16) << 16)
>> +#define EXT4_SIGN_EXT   (~((((1UL << EXT4_EPOCH_BITS) << 16) << 16) - 1))
>>
>> /*
>>  * Extended fields will fit into an inode if the filesystem was formatted
>> @@ -761,19 +763,23 @@ do {                                           \
>>
>> #define EXT4_INODE_GET_XTIME(xtime, inode, raw_inode)                   \
>> do {                                           \
>> -    (inode)->xtime.tv_sec = (signed)le32_to_cpu((raw_inode)->xtime);       \
>> +    (inode)->xtime.tv_sec = (__u64)le32_to_cpu((raw_inode)->xtime);           \
>>    if (EXT4_FITS_IN_INODE(raw_inode, EXT4_I(inode), xtime ## _extra))     \
>>        ext4_decode_extra_time(&(inode)->xtime,                   \
>>                       raw_inode->xtime ## _extra);           \
>>    else                                       \
>>        (inode)->xtime.tv_nsec = 0;                       \
>> +    if (sizeof((inode)->xtime.tv_sec) > 4) {                   \
>> +        if ((inode)->xtime.tv_sec & EXT4_EPOCH_SIGN)               \
>> +            (inode)->xtime.tv_sec |= EXT4_SIGN_EXT;               \
>> +    }                                       \
>> } while (0)
>>
>> #define EXT4_EINODE_GET_XTIME(xtime, einode, raw_inode)                   \
>> do {                                           \
>>    if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime))               \
>>        (einode)->xtime.tv_sec =                       \
>> -            (signed)le32_to_cpu((raw_inode)->xtime);           \
>> +            (__u64)le32_to_cpu((raw_inode)->xtime);               \
>>    else                                       \
>>        (einode)->xtime.tv_sec = 0;                       \
>>    if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime ## _extra))           \
>> @@ -781,6 +787,10 @@ do {                                           \
>>                       raw_inode->xtime ## _extra);           \
>>    else                                       \
>>        (einode)->xtime.tv_nsec = 0;                       \
>> +    if (sizeof((einode)->xtime.tv_sec) > 4) {                   \
>> +        if ((einode)->xtime.tv_sec & EXT4_EPOCH_SIGN)               \
>> +            (einode)->xtime.tv_sec |= EXT4_SIGN_EXT;           \
>> +    }                                       \
>> } while (0)
>>
>> #define i_disk_version osd1.linux1.l_i_version
>> --
>> 1.9.0
>>
--
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