[PATCH] include/cygwin/limits.h: add XATTR_{NAME,SIZE,LIST}_MAX

[Philippe Cerfon]

Hey Corinna, et al.

On Mon, Jun 5, 2023 at 9:05 PM Corinna Vinschen
<corinna-cygwin@cygwin.com> wrote:
> - Whatever that's good for, we actually allow bigger values right
>   now.  For compat reasons we only allow attributes starting with
>   the "user." prefix, and the *trailing* part after "user." is
>   allowed to be 255 bytes long, because we don't store the "user."
>   prefix in the EA name on disk.  So in fact, XATTR_NAME_MAX should
>   be 255 + strlen("user.") == 260.

I haven't given to much though into that right now (just about to go
for 2 weeks on vacation), but if "we" (Cygwin) allow now names up to
260 bytes, because we don't store the "user." .. doesn't that mean
users could set XATTRs, that in the end couldn't be read by e.g. Linux
(should there be, or ever be in the future, support for reading
FAT/NTFS' EAs as XATTRs.... e.g. from the Linux FAT/NTFS fs drivers)?


> - If we actually define these values in limits.h, it would also be a
>   good idea to use them in ntea.cc and to throw away the MAX_EA_*_LEN
>   macros.

Done so in a 2nd commit.
But that commit, right now, really just replaces the name!
MAX_EA_NAME_LEN was set 256, so presumably with the null terminator...
while now it would be set to 260, which seems wrong.

Please just adapt if necessary,... or at least I won't likely be able
to update the patch until in about 2 weeks or so.


Thanks,
Philippe
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-Cygwin-export-XATTR_-NAME-SIZE-LIST-_MAX.patch
Type: text/x-patch
Size: 1099 bytes
Desc: not available
URL: <https://cygwin.com/pipermail/cygwin-patches/attachments/20230606/fc0add34/attachment.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0002-Cygwin-use-new-XATTR_-NAME-SIZE-_MAX-instead-of-MAX_.patch
Type: text/x-patch
Size: 3022 bytes
Desc: not available
URL: <https://cygwin.com/pipermail/cygwin-patches/attachments/20230606/fc0add34/attachment-0001.bin>