[PATCH] Bug in date converting functions DOS<=>UNIX in FAT, NCPFS and SMBFS drivers [second attempt]

[PATCH] Bug in date converting functions DOS<=>UNIX in FAT, NCPFS and SMBFS drivers [second attempt]

[Igor Yu. Zhbanov]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1600 bytes --]

Hello!

Few weeks ago I have sent the following letter:

On Fri, 24 Nov 2000, Igor Yu. Zhbanov wrote:

> Hello!
> 
> I have found a bug in drivers of file systems which use a DOS-like format
> of date (16 bit: years since 1980 - 7 bits, month - 4 bits, day - 5 bits).
> 
> There are two problems:
> 1) It is unable to convert UNIX-like dates before 1980 to DOS-like date format.
> 2) VFAT for example have three kinds of dates: creation date, modification date
>    and access date. Sometimes one of these dates is set to zero (which indicates
>    that this date is not set). Zero is not a valid date (e.g. months are
>    numbered from one, not from zero) and can't be properly converted to
>    UNIX-like format of date (it was converted to date before 1980).
> 
> I have found FAT, NCPFS and SMBFS drivers subject to this problems. Patch for
> fixing these bugs attached.
> 
> Also I have a question about VFAT file system. VFAT have not access time fields
> in directory entries but it has access date fields. Currently information about
> the time of last access is not supported for VFAT file system in LINUX. Is this
> correct? Maybe access time should be truncated to days.
> 
> Thank you.
> 
> P.S. Since I'm not currently subscribed to Linux Kernel Mailing List please CC:
> all replies to bsg@uniyar.ac.ru if any.
> 

As I see now in 2.2.18pre24 NCPFS is fixed but VFAT and SMBFS doesn't. (This
happened because the maintainer of NCPFS resent my patch to Alan Cox but only the
part of patch related to NCPFS). So I resent you patch for VFAT and SMBFS attached
to this letter.

Thank you.

[-- Attachment #2: linux-2.2.17-dosdate.diff --]
[-- Type: TEXT/PLAIN, Size: 2616 bytes --]

diff -ur linux-2.2.17/fs/fat/misc.c linux/fs/fat/misc.c
--- linux-2.2.17/fs/fat/misc.c	Thu May  4 04:16:46 2000
+++ linux/fs/fat/misc.c	Wed Nov 22 14:05:08 2000
@@ -2,6 +2,8 @@
  *  linux/fs/fat/misc.c
  *
  *  Written 1992,1993 by Werner Almesberger
+ *  22/11/2000 - Fixed fat_date_unix2dos for dates earlier than 01/01/1980
+ *		 and date_dos2unix for date==0 by Igor Zhbanov(bsg@uniyar.ac.ru)
  */
 
 #include <linux/fs.h>
@@ -288,7 +290,9 @@
 {
 	int month,year,secs;
 
-	month = ((date >> 5) & 15)-1;
+	/* first subtract and mask after that... Otherwise, if
+	   date == 0, bad things happen */
+	month = ((date >> 5) - 1) & 15;
 	year = date >> 9;
 	secs = (time & 31)*2+60*((time >> 5) & 63)+(time >> 11)*3600+86400*
 	    ((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 &&
@@ -310,6 +314,8 @@
 	unix_date -= sys_tz.tz_minuteswest*60;
 	if (sys_tz.tz_dsttime) unix_date += 3600;
 
+	if (unix_date < 315532800)
+		unix_date = 315532800; /* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
 	*time = (unix_date % 60)/2+(((unix_date/60) % 60) << 5)+
 	    (((unix_date/3600) % 24) << 11);
 	day = unix_date/86400-3652;
diff -ur linux-2.2.17/fs/smbfs/ChangeLog linux/fs/smbfs/ChangeLog
--- linux-2.2.17/fs/smbfs/ChangeLog	Mon Sep  4 21:39:27 2000
+++ linux/fs/smbfs/ChangeLog	Wed Nov 22 14:10:40 2000
@@ -1,5 +1,10 @@
 ChangeLog for smbfs.
 
+2000-11-22 Igor Zhbanov <bsg@uniyar.ac.ru>
+
+	* proc.c: fixed date_unix2dos for dates earlier than 01/01/1980
+	  and date_dos2unix for date==0
+
 2000-07-20 Urban Widmark <urban@svenskatest.se>
 
 	* proc.c: fix 2 places where bad server responses could cause an Oops.
diff -ur linux-2.2.17/fs/smbfs/proc.c linux/fs/smbfs/proc.c
--- linux-2.2.17/fs/smbfs/proc.c	Mon Sep  4 21:39:27 2000
+++ linux/fs/smbfs/proc.c	Wed Nov 22 14:13:32 2000
@@ -169,7 +169,9 @@
 	int month, year;
 	time_t secs;
 
-	month = ((date >> 5) & 15) - 1;
+	/* first subtract and mask after that... Otherwise, if
+	   date == 0, bad things happen */
+	month = ((date >> 5) - 1) & 15;
 	year = date >> 9;
 	secs = (time & 31) * 2 + 60 * ((time >> 5) & 63) + (time >> 11) * 3600 + 86400 *
 	    ((date & 31) - 1 + day_n[month] + (year / 4) + year * 365 - ((year & 3) == 0 &&
@@ -188,6 +190,8 @@
 	int day, year, nl_day, month;
 
 	unix_date = utc2local(server, unix_date);
+	if (unix_date < 315532800)
+		unix_date = 315532800; /* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
 	*time = (unix_date % 60) / 2 +
 		(((unix_date / 60) % 60) << 5) +
 		(((unix_date / 3600) % 24) << 11);

Re: [PATCH] Bug in date converting functions DOS<=>UNIX in FAT, NCPFS and SMBFS drivers [second attempt]

[Urban Widmark]

On Tue, 5 Dec 2000, Igor Yu. Zhbanov wrote:

> Hello!

Hello again

> As I see now in 2.2.18pre24 NCPFS is fixed but VFAT and SMBFS doesn't. (This
> happened because the maintainer of NCPFS resent my patch to Alan Cox but only the
> part of patch related to NCPFS). So I resent you patch for VFAT and SMBFS attached
> to this letter.

Yes. Did you get my letter with questions on day-1?

I'll repeat: As I see it you can end up one day before 1980-01-01 if the
input is all 0 since days are also numbered from 1. Does that need to be
fixed too or is it not a problem?

/Urban

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Re: [PATCH] Bug in date converting functions DOS<=>UNIX in FAT, NCPFS and SMBFS drivers [second attempt]

[Urban Widmark]

On Wed, 13 Dec 2000, Igor Yu. Zhbanov wrote:

> I think your testprogram is broken (or else my testprogram is broken :).

Yes, you were right. Mine must have been broken (possibly caused by
trying to make it readable :). Thanks.

Alan, if you still have the patch please apply it to smbfs in 2.2
(and possibly fat too, I assume it is the same). If you don't I'll send it
again for 2.2.19pre2 or so.

/Urban

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Re: [PATCH] Bug in date converting functions DOS<=>UNIX in FAT, NCPFS and SMBFS drivers [second attempt]

[Igor Yu. Zhbanov]

Hello, sorry for slow response.
(I have lost and found your first letter.)

On Tue, 28 Nov 2000, Urban Widmark wrote:

> On Fri, 24 Nov 2000, Igor Yu. Zhbanov wrote:
>
...
>
> > I have found a bug in drivers of file systems which use a DOS-like format
> > of date (16 bit: years since 1980 - 7 bits, month - 4 bits, day - 5 bits).
>
> [snip]
>
> > 2) VFAT for example have three kinds of dates: creation date, modification date
> >    and access date. Sometimes one of these dates is set to zero (which indicates
> >    that this date is not set). Zero is not a valid date (e.g. months are
> >    numbered from one, not from zero) and can't be properly converted to
> >    UNIX-like format of date (it was converted to date before 1980).
>
> Days are also numbered from one (at least smbfs) and this change doesn't
> do anything about that. An all zero date gives 315446400 (or else my
> testprogram is broken) and you wanted it to give 315532800 (?). So that
> should be fixed too, I think.

I think your testprogram is broken (or else my testprogram is broken :). After applying
my pathch you will get 315532800 (86400*(-1+3653)) on zero date (Jan 1 GMT 00:00:00 1980).
Since 'month = ((date >> 5) & 15) - 1;' is changed to 'month = ((date >> 5) - 1) & 15;'
variable 'month' will be equal to 15 (on zero date) instead of -1. Since day_n[15]==0 you
will get 315532800 (Jan 1 GMT 00:00:00 1980). So nothing to be fixed, I think.

I hope FAT filesystem will be fixed too some day :)

Thank you.

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