On Tue, Apr 27, 2021 at 04:43:05PM +0530, Shreeya Patel wrote: > > On 26/04/21 6:07 pm, Matthew Wilcox wrote: > > On Mon, Apr 26, 2021 at 05:27:51PM +0530, Shreeya Patel wrote: > > > On 26/04/21 6:04 am, Matthew Wilcox wrote: > > > > On Mon, Apr 26, 2021 at 04:01:05AM +0530, Shreeya Patel wrote: > > > > > exFAT filesystem does not support the following character codes > > > > > 0x0000 - 0x001F ( Control Codes ), /, ?, :, ", \, *, <, |, > > > > > ummm ... > > > > > > > > > -# Fake slash? > > > > > -setf "urk\xc0\xafmoo" "FAKESLASH" > > > > That doesn't use any of the explained banned characters. It uses 0xc0, > > > > 0xaf. > > > > > > > > Now, in utf-8, that's an nonconforming sequence. "The Unicode and UCS > > > > standards require that producers of UTF-8 shall use the shortest form > > > > possible, for example, producing a two-byte sequence with first byte 0xc0 > > > > is nonconforming. Unicode 3.1 has added the requirement that conforming > > > > programs must not accept non-shortest forms in their input." > > > > > > > > So is it that exfat is rejecting nonconforming sequences? Or is it > > > > converting the nonconforming sequence from 0xc0 0xaf to the conforming > > > > sequence 0x2f, and then rejecting it (because it's '/')? > > > > > > > No, I don't think exfat is not converting nonconforming sequence from 0xc0 > > > 0xaf > > > to the conforming sequence 0x2f. > > > Because I get different outputs when tried with both ways. > > > When I create a file with "urk\xc0\xafmoo", I get output as "Operation not > > > permitted" > > > and when I create it as "urk\x2fmoo", it gives "No such file or directory > > > error" or > > > you can consider this error as "Invalid argument" > > > ( because that's what I get when I try for other characters like |, :, ?, > > > etc ) > > I think we need to understand this before skipping the test. Does it > > also fail, eg, on cifs, vfat, jfs or udf? > > > I tested it for VFAT, UDF and JFS and following are the results. > > > 1. VFAT ( as per wikipedia 0x00-0x1F 0x7F " * / : < > ? \ | are reserved > characters) > > For \x2f - /var/mnt/scratch/test-453/urk/moo.txt: No such file or directory > > For \xc0\xaf) - /var/mnt/scratch/test-453/urk��moo.txt: Invalid argument > > Also gives error for Box filename > > ( this is very much similar to exfat, the only difference is that I do not > get Operation not permitted when > using \xc0\xaf, instead it gives invalid argument.) vfat checks for those invalid characters, see msdos_format_name() and vfat_is_used_badchars(). TBH I think these tests (g/453 and g/454) are probably only useful for filesystems that allow unrestricted byte streams for names. > 2. UDF ( as per wikipedia - only NULL cannot be used ) > > For \x2f - /var/mnt/scratch/test-453/urk/moo.txt: No such file or directory > > For \xc0\xaf - creates filename something like this 'urk??moo.txt' and does > not throw any error. > ( But this seems to be invalid and should have thrown some error) > > Also gives error for dotdot entry. > > I am not sure why UDF was giving error for / and dot dot entry but then > I read the following for UDF in one of the man pages which justifies the > above errors I think > > "Invalid characters such as "NULL" and "/" and invalid file > names such as "." and ".." will be translated according to > the following rule: > > Replace the invalid character with an "_," then append the > file name with # followed by a 4 digit hex representation of > the 16-bit CRC of the original FileIdentifier. For example, > the file name ".." will become "__#4C05" " > > Source - http://www-it.desy.de/cgi-bin/man-cgi?udfs+7 That's Solaris. > 3. JFS ( as per Wikipedia NULL cannot be used ) > > For \x2f - /var/mnt/scratch/test-453/urk/moo.txt: No such file or directory > > For \xc0\xaf - Works fine > > Again not sure why / is failing here. Did not find much resource about the > restricted filenames for JFS. "/" is a path separator, it should always return ENOENT (unless you created $SCRATCH_MNT/test-453/urk/moo.txt). 0x2f is the ascii encoding for a slash. > So as per above all the results, it seems like using \x2f fails for all but > \xc0\xaf does work for JFS. <nod> --D > > > > > > > Box filename also fails with "Invalid argument" error. > > > > > >
