VFAT: Can't create file named 'aux.h'?

VFAT: Can't create file named 'aux.h'?

[Dirk Reiners]

	Hi everybody,

while trying to back up a couple Linux directories to a FAT disk I ran
into a weird situation: I can't create a file called aux.h on the FAT
system! 

Here's how to reproduce it:

cd /tmp
dd if=/dev/zero of=vfat_img bs=1M count=1
/sbin/losetup /dev/loop7 vfat_img
/sbin/mkfs.vfat /dev/loop7
mkdir vfat_mnt
mount -t vfat /dev/loop7 vfat_mnt
touch vfat_mnt/auy.h
touch vfat_mnt/aux.h

auy.h is happily created, aux.h gives "touch: setting times of
`vfat_mnt/aux.h': No such file or directory", and no file is created.
This happened to me on the system described below, but I could reproduce
the same behavior on a system booted from RHEL4 CDs, an old Knoppix
(3.4), and friends could reproduce it on other systems, too, so it
doesn't seem to be very related to a specific version.

As a workaround I tar/bzipped my dirs, but that behavior seems very
unusual and doesn't inspire a lot of confidence in vfat... What am I
missing here?

Thanks

	Dirk


Here's my system (RHEL4 with updated kernel):

Linux dream.vrac 2.6.15.6 #1 SMP PREEMPT Tue Mar 14 10:41:05 CST 2006
x86_64 x86_64 x86_64 GNU/Linux

Gnu C                  3.4.3
Gnu make               3.80
binutils               2.15.92.0.2
util-linux             2.12a
mount                  2.12a
module-init-tools      3.1-pre5
e2fsprogs              1.35
reiserfsprogs          line
reiser4progs           line
pcmcia-cs              3.2.7
quota-tools            3.12.
PPP                    2.4.2
nfs-utils              1.0.6
Linux C Library        2.3.4
Dynamic linker (ldd)   2.3.4
Procps                 3.2.3
Net-tools              1.60
Kbd                    1.12
Sh-utils               5.2.1
udev                   039
Modules Loaded         loop vmnet vmmon parport_pc lp parport autofs4
sunrpc ipt_REJECT ipt_state ip_conntrack iptable_filter ip_tables vfat
fat dm_mod button battery ac nvidia ipv6 usb_storage ohci1394 ohci_hcd
ehci_hcd i2c_nforce2 i2c_core snd_intel8x0 snd_ac97_codec snd_ac97_bus
snd_pcm_oss snd_mixer_oss snd_pcm snd_timer snd soundcore snd_page_alloc
forcedeth floppy raid0 sata_nv libata sd_mod scsi_mod

Re: VFAT: Can't create file named 'aux.h'?

[Randy.Dunlap]

On Mon, 20 Mar 2006 15:40:22 -0600 Dirk Reiners wrote:

> 
> 	Hi everybody,
> 
> while trying to back up a couple Linux directories to a FAT disk I ran
> into a weird situation: I can't create a file called aux.h on the FAT
> system! 
> 
> Here's how to reproduce it:
> 
> cd /tmp
> dd if=/dev/zero of=vfat_img bs=1M count=1
> /sbin/losetup /dev/loop7 vfat_img
> /sbin/mkfs.vfat /dev/loop7
> mkdir vfat_mnt
> mount -t vfat /dev/loop7 vfat_mnt
> touch vfat_mnt/auy.h
> touch vfat_mnt/aux.h
> 
> auy.h is happily created, aux.h gives "touch: setting times of
> `vfat_mnt/aux.h': No such file or directory", and no file is created.
> This happened to me on the system described below, but I could reproduce
> the same behavior on a system booted from RHEL4 CDs, an old Knoppix
> (3.4), and friends could reproduce it on other systems, too, so it
> doesn't seem to be very related to a specific version.
> 
> As a workaround I tar/bzipped my dirs, but that behavior seems very
> unusual and doesn't inspire a lot of confidence in vfat... What am I
> missing here?

"AUX" is (was) a reserved "filename" in DOS.  The Linux MS-DOS
filesystem preserves (protects) that.  The extension part does not
matter; it only checks the first 8 characters of the filename.
You'll need to use a different filesystem or filename...


fs/msdos/namei.c:

		for (reserved = reserved_names; *reserved; reserved++)
			if (!strncmp(res, *reserved, 8))
				return -EINVAL;

/* MS-DOS "device special files" */
static const unsigned char *reserved_names[] = {
	"CON     ", "PRN     ", "NUL     ", "AUX     ",
	"LPT1    ", "LPT2    ", "LPT3    ", "LPT4    ",
	"COM1    ", "COM2    ", "COM3    ", "COM4    ",
	NULL
};


---
~Randy

Re: VFAT: Can't create file named 'aux.h'?

[Jan Engelhardt]

>	Hi everybody,
>
>while trying to back up a couple Linux directories to a FAT disk I ran
>into a weird situation: I can't create a file called aux.h on the FAT
>system! 
>
On DOS et al, there are a number of special filenames, such as

	com1:
	com2: (and so on)
	lpt1:
	lpt2: (and so on)
	con:
	aux
	nul

(Try `dir >nul`, it's equivalent to unix's `ls -l >/dev/null` --
aux is the auxiliary port, whatever that is)

It seems only fair to me to not allow creating these files under Linux 
either, to avoid problems when booting back to Dos/Windows.


Jan Engelhardt
-- 
| Software Engineer and Linux/Unix Network Administrator

Re: VFAT: Can't create file named 'aux.h'?

[H. Peter Anvin]

Followup to:  <20060320134533.febb0155.rdunlap@xenotime.net>
By author:    "Randy.Dunlap" <rdunlap@xenotime.net>
In newsgroup: linux.dev.kernel
> 
> "AUX" is (was) a reserved "filename" in DOS.  The Linux MS-DOS
> filesystem preserves (protects) that.  The extension part does not
> matter; it only checks the first 8 characters of the filename.
> You'll need to use a different filesystem or filename...
> 

But this is VFAT, not FAT.  It should probably take the reserved name
and mangle it.

> 
> /* MS-DOS "device special files" */
> static const unsigned char *reserved_names[] = {
> 	"CON     ", "PRN     ", "NUL     ", "AUX     ",
> 	"LPT1    ", "LPT2    ", "LPT3    ", "LPT4    ",
> 	"COM1    ", "COM2    ", "COM3    ", "COM4    ",
> 	NULL
> };
> 

There should be more than that.  At the very least there is "CLOCK$"
(arguably anything with $), "MSCD001" (and probably more than 001), as
well as "COM5".."COM8".

	-hpa

Re: VFAT: Can't create file named 'aux.h'?

[linux-os (Dick Johnson)]

On Mon, 20 Mar 2006, Dirk Reiners wrote:

>
> 	Hi everybody,
>
> while trying to back up a couple Linux directories to a FAT disk I ran
> into a weird situation: I can't create a file called aux.h on the FAT
> system!
>
> Here's how to reproduce it:
>
> cd /tmp
> dd if=/dev/zero of=vfat_img bs=1M count=1
> /sbin/losetup /dev/loop7 vfat_img
> /sbin/mkfs.vfat /dev/loop7
> mkdir vfat_mnt
> mount -t vfat /dev/loop7 vfat_mnt
> touch vfat_mnt/auy.h
> touch vfat_mnt/aux.h
>
> auy.h is happily created, aux.h gives "touch: setting times of
> `vfat_mnt/aux.h': No such file or directory", and no file is created.
> This happened to me on the system described below, but I could reproduce
> the same behavior on a system booted from RHEL4 CDs, an old Knoppix
> (3.4), and friends could reproduce it on other systems, too, so it
> doesn't seem to be very related to a specific version.
>
> As a workaround I tar/bzipped my dirs, but that behavior seems very
> unusual and doesn't inspire a lot of confidence in vfat... What am I
> missing here?
>
> Thanks
>
> 	Dirk

[SNIPPED...]

Special file under DOS: "CON", "AUX", "PRN", and a few others! The
"extension" isn't checked.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.48 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_
\x1a\x04

****************************************************************
The information transmitted in this message is confidential and may be privileged.  Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited.  If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to DeliveryErrors@analogic.com - and destroy all copies of this information, including any attachments, without reading or disclosing them.

Thank you.

Re: VFAT: Can't create file named 'aux.h'?

[Phillip Susi]

Why on earth does linux enforce this restriction?  I'm not sure about dos ( it has been 10+ years since I used it ), but NT will happily create files with those names on either fat or ntfs, provided that you refer to them with an absolute path name.  Seeing as how it wasn't really a restriction on the filesystem itself, but rather the fact that those names were predefined by io.sys, I see no reason why linux should prevent you from using them.  

Randy.Dunlap wrote:
> "AUX" is (was) a reserved "filename" in DOS.  The Linux MS-DOS
> filesystem preserves (protects) that.  The extension part does not
> matter; it only checks the first 8 characters of the filename.
> You'll need to use a different filesystem or filename...
> 
> 
> fs/msdos/namei.c:
> 
> 		for (reserved = reserved_names; *reserved; reserved++)
> 			if (!strncmp(res, *reserved, 8))
> 				return -EINVAL;
> 
> /* MS-DOS "device special files" */
> static const unsigned char *reserved_names[] = {
> 	"CON     ", "PRN     ", "NUL     ", "AUX     ",
> 	"LPT1    ", "LPT2    ", "LPT3    ", "LPT4    ",
> 	"COM1    ", "COM2    ", "COM3    ", "COM4    ",
> 	NULL
> };
> 
> 

Re: VFAT: Can't create file named 'aux.h'?

[Randy.Dunlap]

On Mon, 20 Mar 2006 23:28:19 -0500 Phillip Susi wrote:

> Why on earth does linux enforce this restriction?  I'm not sure about dos ( it has been 10+ years since I used it ), but NT will happily create files with those names on either fat or ntfs, provided that you refer to them with an absolute path name.  Seeing as how it wasn't really a restriction on the filesystem itself, but rather the fact that those names were predefined by io.sys, I see no reason why linux should prevent you from using them.  

The only reason that I could come close to seeing is backwards
compatibility:  moving a disk+filesystem back to a real DOS
environment.  But that's just not very likely...


> Randy.Dunlap wrote:
> > "AUX" is (was) a reserved "filename" in DOS.  The Linux MS-DOS
> > filesystem preserves (protects) that.  The extension part does not
> > matter; it only checks the first 8 characters of the filename.
> > You'll need to use a different filesystem or filename...
> > 
> > 
> > fs/msdos/namei.c:
> > 
> > 		for (reserved = reserved_names; *reserved; reserved++)
> > 			if (!strncmp(res, *reserved, 8))
> > 				return -EINVAL;
> > 
> > /* MS-DOS "device special files" */
> > static const unsigned char *reserved_names[] = {
> > 	"CON     ", "PRN     ", "NUL     ", "AUX     ",
> > 	"LPT1    ", "LPT2    ", "LPT3    ", "LPT4    ",
> > 	"COM1    ", "COM2    ", "COM3    ", "COM4    ",
> > 	NULL
> > };

---
~Randy

Re: VFAT: Can't create file named 'aux.h'?

[Yaroslav Rastrigin]

Hi, 
On 21 March 2006 00:46, you wrote:
> >	Hi everybody,
> >
> >while trying to back up a couple Linux directories to a FAT disk I ran
> >into a weird situation: I can't create a file called aux.h on the FAT
> >system! 
> >
> On DOS et al, there are a number of special filenames, such as
> 
> 	com1:
> 	com2: (and so on)
> 	lpt1:
> 	lpt2: (and so on)
> 	con:
> 	aux
> 	nul
> 
> (Try `dir >nul`, it's equivalent to unix's `ls -l >/dev/null` --
> aux is the auxiliary port, whatever that is)
> 
> It seems only fair to me to not allow creating these files under Linux 
> either, to avoid problems when booting back to Dos/Windows.
This is true. smbfs, OTOH, has no such checks, so creating aux.h on an smb share is one easy way to DoS 
all WinXP machines using(browsing) this share. Explorer hangs on reading directory with this file.
> 
> 
> Jan Engelhardt

-- 
Managing your Territory since the dawn of times ...

Re: VFAT: Can't create file named 'aux.h'?

[Jan-Benedict Glaw]

[-- Attachment #1: Type: text/plain, Size: 1186 bytes --]

On Mon, 2006-03-20 13:50:29 -0800, H. Peter Anvin <hpa@zytor.com> wrote:
> > /* MS-DOS "device special files" */
> > static const unsigned char *reserved_names[] = {
> > 	"CON     ", "PRN     ", "NUL     ", "AUX     ",
> > 	"LPT1    ", "LPT2    ", "LPT3    ", "LPT4    ",
> > 	"COM1    ", "COM2    ", "COM3    ", "COM4    ",
> > 	NULL
> > };
> > 
> 
> There should be more than that.  At the very least there is "CLOCK$"
> (arguably anything with $), "MSCD001" (and probably more than 001), as
> well as "COM5".."COM8".

Please divide all the reservednames into two groups: those build-in
into io.sys/msdos.sys/command.com and those that are added on the fly.
For example, "mscd001" is runtime-registered trhough any atapi CD-ROM
driver and this name is/was usually a user-configurable option. (Bad
guys name it 'README'.)

MfG, JBG

-- 
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Re: VFAT: Can't create file named 'aux.h'?

[linux-os (Dick Johnson)]

On Tue, 21 Mar 2006, Yaroslav Rastrigin wrote:

> Hi,
> On 21 March 2006 00:46, you wrote:
>>> 	Hi everybody,
>>>
>>> while trying to back up a couple Linux directories to a FAT disk I ran
>>> into a weird situation: I can't create a file called aux.h on the FAT
>>> system!
>>>
>> On DOS et al, there are a number of special filenames, such as
>>
>> 	com1:
>> 	com2: (and so on)
>> 	lpt1:
>> 	lpt2: (and so on)
>> 	con:
>> 	aux
>> 	nul
>>
>> (Try `dir >nul`, it's equivalent to unix's `ls -l >/dev/null` --
>> aux is the auxiliary port, whatever that is)
>>
>> It seems only fair to me to not allow creating these files under Linux
>> either, to avoid problems when booting back to Dos/Windows.
> This is true. smbfs, OTOH, has no such checks, so creating aux.h on an smb share is one easy way to DoS
> all WinXP machines using(browsing) this share. Explorer hangs on reading directory with this file.
>>
>>
>> Jan Engelhardt
>
> --
> Managing your Territory since the dawn of times ...

Also, CON is a sensitive name on WIN/2000. This can hang the
browser. The "@#+^%!@#" devices still exist:

C:\> copy con xxx.xxx

.... from the shell will wait forever.



Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.48 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_
\x1a\x04

****************************************************************
The information transmitted in this message is confidential and may be privileged.  Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited.  If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to DeliveryErrors@analogic.com - and destroy all copies of this information, including any attachments, without reading or disclosing them.

Thank you.

Re: VFAT: Can't create file named 'aux.h'?

[Phillip Susi]

linux-os (Dick Johnson) wrote:
> 
> Also, CON is a sensitive name on WIN/2000. This can hang the
> browser. The "@#+^%!@#" devices still exist:
> 
> C:\> copy con xxx.xxx
> 
> .... from the shell will wait forever.
> 

Not quite.  This is the same as doing a cp /dev/stdin xxx.xxx on linux. 
  It will read from stdin until it sees an EOF.  On windows, eof is 
ctrl-z instead of ctrl-d; hit that and the copy command will finish.

Re: VFAT: Can't create file named 'aux.h'?

[Phillip Susi]

I disagree with this philosophy seeing as how it is possible to create 
these files from within windows itself:

echo foo > \\?\c:\aux.h
dir *.h
  Volume in drive C has no label.
  Volume Serial Number is F064-30D6

  Directory of C:\

03/21/2006  10:07a                   6 aux.h
                1 File(s)              6 bytes
                0 Dir(s)   4,584,951,808 bytes free

Creates a file named aux.h in c:\ just fine.  Under win2k at least, 
explorer only hangs when I try to click on the file.  Explorer has 
always done really stupid things like this though.  I remember when 95 
first came out we could create files with high ascii names on the server 
like ascii 255, and explorer would happily render it as an underscore 
(_), but could not open it or delete it because it was actually trying 
to access a directory named "_" rather than ascii 255.

Just because explorer/the win32 api is stupid doesn't mean linux should 
be too.

Yaroslav Rastrigin wrote:
>> It seems only fair to me to not allow creating these files under Linux 
>> either, to avoid problems when booting back to Dos/Windows.
> This is true. smbfs, OTOH, has no such checks, so creating aux.h on an smb share is one easy way to DoS 
> all WinXP machines using(browsing) this share. Explorer hangs on reading directory with this file.
>>
>> Jan Engelhardt
> 

Re: VFAT: Can't create file named 'aux.h'?

[Jan Engelhardt]

>> "AUX" is (was) a reserved "filename" in DOS.  The Linux MS-DOS
>> filesystem preserves (protects) that.  The extension part does not
>> matter; it only checks the first 8 characters of the filename.
>> You'll need to use a different filesystem or filename...
>
>But this is VFAT, not FAT.  It should probably take the reserved name
>and mangle it.
>
NAK. How much more names will you be going to mangle because of FAT 
character restrictions? (< and > are one of the chars not allowed in FAT.)

>There should be more than that.  At the very least there is "CLOCK$"
>(arguably anything with $), "MSCD001" (and probably more than 001), as
>well as "COM5".."COM8".
>
Objection too. You can create these files without a problem within Win98, 
so it shall remain possible under Linux too.


Jan Engelhardt
-- 
| Software Engineer and Linux/Unix Network Administrator

Re: VFAT: Can't create file named 'aux.h'?

[Jan Engelhardt]

>> It seems only fair to me to not allow creating these files under Linux 
>> either, to avoid problems when booting back to Dos/Windows.
>
>This is true. smbfs, OTOH, has no such checks, so creating aux.h on an smb share is one easy way to DoS 
>all WinXP machines using(browsing) this share. Explorer hangs on reading directory with this file.

BTW, what about cifs? And after all, this is not a smbfs check,
but it is something that should be done on the server side.
If you use smbfs to connect two Linux machines, you should be
able to create all the weird names you can imagine (with respect
to what the smb protocol allows). If you have a Windows machine
as the smbfs server, creating 'special files' should be limited
by whatever Windows sees fit.



Jan Engelhardt
-- 
| Software Engineer and Linux/Unix Network Administrator

Re: VFAT: Can't create file named 'aux.h'?

[H. Peter Anvin]

Jan Engelhardt wrote:
> 
> NAK. How much more names will you be going to mangle because of FAT 
> character restrictions? (< and > are one of the chars not allowed in FAT.)
> 

Uhm... that's what VFAT *does*...

	-hpa

Re: VFAT: Can't create file named 'aux.h'?

[Jan Engelhardt]

>> NAK. How much more names will you be going to mangle because of FAT
>> character restrictions? (< and > are one of the chars not allowed in FAT.)
>
> Uhm... that's what VFAT *does*...
>
Hm. How do I check? Under a DOS shell,

	echo bla >"illegal>name"

won't work, and creating a new empty dummy text file within Windows 
Explorer with this illegal>name won't work either.
(http://jengelh.hopto.org/f/illegal_filename.jpg)
Did I miss some magic WINAPI function that does allow it implicitly
by mangling the name?


Jan Engelhardt
-- 
| Software Engineer and Linux/Unix Network Administrator

Re: VFAT: Can't create file named 'aux.h'?

[H. Peter Anvin]

Jan Engelhardt wrote:
>>>NAK. How much more names will you be going to mangle because of FAT
>>>character restrictions? (< and > are one of the chars not allowed in FAT.)
>>
>>Uhm... that's what VFAT *does*...
>>
> 
> Hm. How do I check? Under a DOS shell,
> 
> 	echo bla >"illegal>name"
> 
> won't work, and creating a new empty dummy text file within Windows 
> Explorer with this illegal>name won't work either.
> (http://jengelh.hopto.org/f/illegal_filename.jpg)
> Did I miss some magic WINAPI function that does allow it implicitly
> by mangling the name?

You're confusing characters which aren't legal *VFAT* names which those 
which aren't legal *FAT* (8.3) names.

 > is illegal in VFAT as well.

	-hpa

Re: VFAT: Can't create file named 'aux.h'?

[Jan Engelhardt]

>
> You're confusing characters which aren't legal *VFAT* names which those which
> aren't legal *FAT* (8.3) names.
>
Could you please name an illegal FAT name being legal VFAT name?


Jan Engelhardt
-- 

Re: VFAT: Can't create file named 'aux.h'?

[H. Peter Anvin]

Jan Engelhardt wrote:
>>You're confusing characters which aren't legal *VFAT* names which those which
>>aren't legal *FAT* (8.3) names.
>>
> 
> Could you please name an illegal FAT name being legal VFAT name?
> 

"Green Furry Submarine"

	-hpa

Re: VFAT: Can't create file named 'aux.h'?

[Jan Engelhardt]

>> > You're confusing characters which aren't legal *VFAT* names which those
>> > which
>> > aren't legal *FAT* (8.3) names.
>> 
>> Could you please name an illegal FAT name being legal VFAT name?
>
> "Green Furry Submarine"
>
Ah well. But aux.h is also forbidden under VFAT, is not it? Or no, because 
it's "just" an 8.3 name?


Jan Engelhardt
-- 
| Software Engineer and Linux/Unix Network Administrator

Re: VFAT: Can't create file named 'aux.h'?

[H. Peter Anvin]

Jan Engelhardt wrote:
>>>>You're confusing characters which aren't legal *VFAT* names which those
>>>>which
>>>>aren't legal *FAT* (8.3) names.
>>>
>>>Could you please name an illegal FAT name being legal VFAT name?
>>
>>"Green Furry Submarine"
>>
> 
> Ah well. But aux.h is also forbidden under VFAT, is not it? Or no, because 
> it's "just" an 8.3 name?
> 

It probably depends on how picky you want to be.  As far as I know, even 
NT will recognize a character device name without leaving \DEV\, even 
though \DEV\ has been the "official" device prefix since DOS 2.0.

Probably it would be worth trying to create "aux.h" under XP and see 
what happens.  Unfortunately I don't have a 'doze system handy at the 
moment.

	-hpa

Re: VFAT: Can't create file named 'aux.h'?

[Vadim Lobanov]

On Tue, 21 Mar 2006, H. Peter Anvin wrote:

> Jan Engelhardt wrote:
> >>>>You're confusing characters which aren't legal *VFAT* names which those
> >>>>which
> >>>>aren't legal *FAT* (8.3) names.
> >>>
> >>>Could you please name an illegal FAT name being legal VFAT name?
> >>
> >>"Green Furry Submarine"
> >>
> >
> > Ah well. But aux.h is also forbidden under VFAT, is not it? Or no, because
> > it's "just" an 8.3 name?
> >
>
> It probably depends on how picky you want to be.  As far as I know, even
> NT will recognize a character device name without leaving \DEV\, even
> though \DEV\ has been the "official" device prefix since DOS 2.0.
>
> Probably it would be worth trying to create "aux.h" under XP and see
> what happens.  Unfortunately I don't have a 'doze system handy at the
> moment.

Fails silently.

> 	-hpa
>
> -

Vadim Lobanov

Re: VFAT: Can't create file named 'aux.h'?

[John Stoffel]

>>>>> "H" == H Peter Anvin <hpa@zytor.com> writes:

H> It probably depends on how picky you want to be.  As far as I know,
H> even NT will recognize a character device name without leaving
H> \DEV\, even though \DEV\ has been the "official" device prefix
H> since DOS 2.0.

H> Probably it would be worth trying to create "aux.h" under XP and
H> see what happens.  Unfortunately I don't have a 'doze system handy
H> at the moment.

Unfortunately I do.  The desktop won't let me create a file named
'aux' or 'aux.h' at all.  I tried fooling it with 'auxx' and then
renaming it it 'aux' but it won't let me using the mouse stuff.

Still wouldn't let me create that name from the 'cmd' shell either.  

John

Re: VFAT: Can't create file named 'aux.h'?

[Phillip Susi]

H. Peter Anvin wrote:
> Probably it would be worth trying to create "aux.h" under XP and see 
> what happens.  Unfortunately I don't have a 'doze system handy at the 
> moment.

kernel32.dll's CreateFile() and other apis normally perform translation 
which includes special handling for dos device names including AUX.  You 
can bypass this by prefixing the absolute file name with the string 
"\\?\" and this will allow you to create a file named AUX.  It also 
allows you to reference file names with absolute paths greater than 255 
characters.

RE: VFAT: Can't create file named 'aux.h'?

[Hua Zhong]

It's more "treating aux.* the same way as aux". It doesn't fail per se. If
you do "echo test >con.h", it will print to the screen.

> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-
> owner@vger.kernel.org] On Behalf Of Vadim Lobanov
> Sent: Tuesday, March 21, 2006 11:55 AM
> To: H. Peter Anvin
> Cc: Jan Engelhardt; linux-kernel@vger.kernel.org
> Subject: Re: VFAT: Can't create file named 'aux.h'?
> 
> On Tue, 21 Mar 2006, H. Peter Anvin wrote:
> 
> > Jan Engelhardt wrote:
> > >>>>You're confusing characters which aren't legal *VFAT* names which
> those
> > >>>>which
> > >>>>aren't legal *FAT* (8.3) names.
> > >>>
> > >>>Could you please name an illegal FAT name being legal VFAT name?
> > >>
> > >>"Green Furry Submarine"
> > >>
> > >
> > > Ah well. But aux.h is also forbidden under VFAT, is not it? Or no,
> because
> > > it's "just" an 8.3 name?
> > >
> >
> > It probably depends on how picky you want to be.  As far as I know, even
> > NT will recognize a character device name without leaving \DEV\, even
> > though \DEV\ has been the "official" device prefix since DOS 2.0.
> >
> > Probably it would be worth trying to create "aux.h" under XP and see
> > what happens.  Unfortunately I don't have a 'doze system handy at the
> > moment.
> 
> Fails silently.
> 
> > 	-hpa
> >
> > -
> 
> Vadim Lobanov
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: VFAT: Can't create file named 'aux.h'?

[Paul Jackson]

hpa wrote:
> Probably it would be worth trying to create "aux.h" under XP and see 
> what happens.  Unfortunately I don't have a 'doze system handy at the 
> moment.

On my windows xp box, I just ran the following three experiments,
all inside a window brought up by running Start->Run "cmd":
 
 C:\ copy con foo
 blah blah blah
 ^Z

 C:\ copy con aux
 blah blah blah

 C:\ copy con aux.h
 blah blah blah

The first experiment above created a file named 'foo',
containing 'blah blah blah'

The second and third experiments both returned to the
command prompt when I pressed "Enter" at the end of the
"blah blah blah", after first complaining:

   The system cannot find the file specified.
           0 file(s) copied.

This is on a fairly vanilla and uptodate Windows XP SP2.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: VFAT: Can't create file named 'aux.h'?

[H. Peter Anvin]

Phillip Susi wrote:
> H. Peter Anvin wrote:
> 
>> Probably it would be worth trying to create "aux.h" under XP and see 
>> what happens.  Unfortunately I don't have a 'doze system handy at the 
>> moment.
> 
> 
> kernel32.dll's CreateFile() and other apis normally perform translation 
> which includes special handling for dos device names including AUX.  You 
> can bypass this by prefixing the absolute file name with the string 
> "\\?\" and this will allow you to create a file named AUX.  It also 
> allows you to reference file names with absolute paths greater than 255 
> characters.
> 

So, in other words, Windows will let you create these files; it will 
just make you just through hoops to access them.

Sounds like they should be able to be legitimately created.  If the 
shortnames are mangled, even DOS or Win9x could access them using the 
shortname.

	-hpa

Re: VFAT: Can't create file named 'aux.h'?

[OGAWA Hirofumi]

"H. Peter Anvin" <hpa@zytor.com> writes:

> Phillip Susi wrote:
>> H. Peter Anvin wrote:
>> 
>> kernel32.dll's CreateFile() and other apis normally perform translation 
>> which includes special handling for dos device names including AUX.  You 
>> can bypass this by prefixing the absolute file name with the string 
>> "\\?\" and this will allow you to create a file named AUX.  It also 
>> allows you to reference file names with absolute paths greater than 255 
>> characters.
>
> So, in other words, Windows will let you create these files; it will 
> just make you just through hoops to access them.
>
> Sounds like they should be able to be legitimately created.  If the 
> shortnames are mangled, even DOS or Win9x could access them using the 
> shortname.

Looks like we get a good reason to kill strange reserved names in vfat
(and msdos too?).

Could you/anyone check what shortname is used for "AUX" if it is created
in cmd.exe?

Windows may be storing it as shortname, because it seems to be using
completely separated namespace for devices (I guessed from result of
google).

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: VFAT: Can't create file named 'aux.h'?

[Ulrich Mueller]

>>>>> H. Peter Anvin wrote:

> Sounds like they should be able to be legitimately created.  If the
> shortnames are mangled, even DOS or Win9x could access them using the
> shortname.

This looks like a mount option is needed. Actually, FAT already has an
option "check={relaxed,normal,strict}".

For example, creation of these files could be enabled in case of
"check=relaxed" (the following is untested):

--- linux-2.6.16/fs/msdos/namei.c~	2006-03-20 12:32:03.000000000 +0100
+++ linux-2.6.16/fs/msdos/namei.c	2006-03-22 22:37:46.000000000 +0100
@@ -127,7 +127,7 @@
 	}
 	while (walk - res < MSDOS_NAME)
 		*walk++ = ' ';
-	if (!opts->atari)
+	if (!opts->atari && opts->name_check != 'r')
 		/* GEMDOS is less stupid and has no reserved names */
 		for (reserved = reserved_names; *reserved; reserved++)
 			if (!strncmp(res, *reserved, 8))

Cheers
Uli

Re: VFAT: Can't create file named 'aux.h'?

[Phillip Susi]

It appears to simply be stored as "aux" under windows.  The filesystem 
itself has no reserved names.  The handling of AUX and CON and friends 
is just special case handling done at the win32 api level.

OGAWA Hirofumi wrote:
> Could you/anyone check what shortname is used for "AUX" if it is created
> in cmd.exe?
> 
> Windows may be storing it as shortname, because it seems to be using
> completely separated namespace for devices (I guessed from result of
> google).
> 
> Thanks.

Re: VFAT: Can't create file named 'aux.h'?

[linux-os (Dick Johnson)]

On Wed, 22 Mar 2006, Phillip Susi wrote:

> It appears to simply be stored as "aux" under windows.  The filesystem
> itself has no reserved names.  The handling of AUX and CON and friends
> is just special case handling done at the win32 api level.
>
> OGAWA Hirofumi wrote:
>> Could you/anyone check what shortname is used for "AUX" if it is created
>> in cmd.exe?
>>
>> Windows may be storing it as shortname, because it seems to be using
>> completely separated namespace for devices (I guessed from result of
>> google).
>>
>> Thanks.
>

Under win/2000 "aux" can't be created either by using C/C++ or
any of the usual utilities like `ftp`. The returned error-code
is "Permission denied", even from an administrator account.

I have a dual-boot lap-top so I tried to create a file called
"AUX" using `echo "">AUX`, under Linux-2.4.26. The error-code
was "Invalid argument". This is a "vfat" file-system. I was
able to create the device-name "CLOCK$", which is reserved in
DOS. I'm now rebooting the laptop, it should be interesting
to see if it still works! .... Yep. It's not a reserved name
in Win/2000.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.48 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_
\x1a\x04

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Re: VFAT: Can't create file named 'aux.h'?

[Phillip Susi]

linux-os (Dick Johnson) wrote:
> Under win/2000 "aux" can't be created either by using C/C++ or
> any of the usual utilities like `ftp`. The returned error-code
> is "Permission denied", even from an administrator account.
> 

For the third time this thread, yes, you can, you just have to escape 
the path name to prevent the win32 api from translating the name to the 
non existent AUX device.  From a command line you can do:

echo foo > \\?\c:\aux

And it will work just fine.  The only place the name "AUX" has any 
meaning is in the win32 api layers that translate certain device names 
to the real kernel path.  The kernel and filesystem will store whatever 
name you choose for compatibility with the posix subsystem.

> I have a dual-boot lap-top so I tried to create a file called
> "AUX" using `echo "">AUX`, under Linux-2.4.26. The error-code
> was "Invalid argument". This is a "vfat" file-system. I was
> able to create the device-name "CLOCK$", which is reserved in
> DOS. I'm now rebooting the laptop, it should be interesting
> to see if it still works! .... Yep. It's not a reserved name
> in Win/2000.
> 

Re: VFAT: Can't create file named 'aux.h'?

[OGAWA Hirofumi]

René Scharfe <rene.scharfe@lsrfire.ath.cx> writes:

> OGAWA Hirofumi schrieb:
>> Looks like we get a good reason to kill strange reserved names in vfat
>> (and msdos too?).
>> 
>> Could you/anyone check what shortname is used for "AUX" if it is created
>> in cmd.exe?
>
> on Windows XP Home SP2 I did:
>
>    mkdir d:\test
>    cd /d d:\test
>    echo 1 > \\?\d:\test\aux
>    echo 2 > \\?\d:\test\nul
>    echo 3 > \\?\d:\test\nul.x
>    echo 4 > \\?\d:\test\nul.longext
>    echo 5 > \\?\d:\test\...
>    echo 6 > "\\?\d:\test\[];,+="
>    echo 7 > "\\?\d:\test\   "
>    dir /x > a.txt
>
> And here's the contents of a.txt:
>
> --- snip! ---
>  Datenträger in Laufwerk D: ist 53_00_00
>  Volumeseriennummer: 1002-884F
>
>  Verzeichnis von D:\test
>
> 23.03.2006  12:21    <DIR>                       .
> 23.03.2006  12:21    <DIR>                       ..
> 23.03.2006  12:21                 4 0103~1
> 23.03.2006  12:21                 4 7154~1       ...
> 23.03.2006  12:21                 0              a.txt
> 23.03.2006  12:21                 4              aux
> 23.03.2006  12:21                 4              nul
> 23.03.2006  12:21                 4 NUL~1.LON    nul.longext
> 23.03.2006  12:21                 4              nul.x
> 23.03.2006  12:21                 4 ______~1     [];,+=
>                8 Datei(en)             28 Bytes
>                2 Verzeichnis(se), 31.506.370.560 Bytes frei
> --- snip! ---
>
> So, no shortname is created for aux on my machine.

Thanks, Phillip and Rene.

It seems the shortname. Because "a.txt" is using same form, and
"no shortname" is meaning a "broken directory entry" in fat spec.

> Of course that doesn't prevent us from creating one in vfat, right?

Yes. We would not need special case for devices.

I'll remove reserved names from vfat/msdos, because many OSes/commands
(even Windows) creates it.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>