ad: segfault when modifying files on volume owned by other user

[rdmark]

If you run ad cp or ad mv (etc.) on a file on a shared volume where the user running ad is also the owner of the dir/files on the shared volume, the operations succeed without issue.

However, if the dir/files are owned by another user, ad throws a segfault.

This is not a new bug. I could reproduce as far back as 3.1.12.

dmark@pretrix:/srv/afptest1$ ad cp 1 11
Mar 15 15:13:05.099331 ad[125273] {netatalk_conf.c:2024} (error:Default): getvolbypath("/srv/afptest1/11"): path does not match basedir regex "/home"
Mar 15 15:13:05.099435 ad[125273] {netatalk_conf.c:2024} (error:Default): getvolbypath("/srv/afptest1/1"): path does not match basedir regex "/home"
Segmentation fault

Sample backtrace

Program received signal SIGSEGV, Segmentation fault.
copy (path=0xaaaaaaaca850 "README", statp=0xffffffffc6d0, tflag=0, ftw=0xffffffffc778) at ../bin/ad/ad_cp.c:376
376	    if (!dvolume.vol->vfs->vfs_validupath(dvolume.vol, dir))
(gdb) bt
#0  copy (path=0xaaaaaaaca850 "README", statp=0xffffffffc6d0, tflag=0, ftw=0xffffffffc778) at ../bin/ad/ad_cp.c:376
#1  0x0000fffff7f4dea8 in ftw_startup (dir=0xfffffffff6ff "README", is_nftw=1, func=0xaaaaaaaa3694 <copy>, 
    up=0xaaaaaaaa2d28 <upfunc>, descriptors=20, flags=19) at ../libatalk/util/ftw.c:817
#2  0x0000fffff7f4dfc4 in nftw (path=0xfffffffff6ff "README", func=0xaaaaaaaa3694 <copy>, up=0xaaaaaaaa2d28 <upfunc>, 
    descriptors=20, flags=19) at ../libatalk/util/ftw.c:862
#3  0x0000aaaaaaaa35d4 in ad_cp (argc=1, argv=0xfffffffff498, obj=0xffffffffc990) at ../bin/ad/ad_cp.c:338
#4  0x0000aaaaaaaaa568 in main (argc=4, argv=0xfffffffff488) at ../bin/ad/ad.c:68