False positive from access("/proc/registry/...", F_OK)

[Christian Franke]

access("/proc/registry/...", F_OK) returns 0 for all (including
nonexistent) entries below a registry key which cannot be opened:

Testcase (run with admin rights):

# cygcheck -f /bin/cygwin1.dll
cygwin-1.7.9-1

# cd /proc/registry/HKEY_LOCAL_MACHINE

# ls SECURITY
Cache  Policy  RXACT  SAM

# cygdrop -- ls SECURITY
ls: reading directory SECURITY: Permission denied

# test -e SECURITY/NoSuchFile && echo yes

# cygdrop -- test -e SECURITY/NoSuchFile && echo yes
yes


Problem was likely introduced by fhandler_registry.cc change 1.52:

 fhandler_registry::exists ()
 ...
   if (!val_only)
     hKey = open_key (path, KEY_READ, wow64, false);
 - if (hKey != (HKEY) INVALID_HANDLE_VALUE)
 + if (hKey != (HKEY) INVALID_HANDLE_VALUE || get_errno () == EACCES)
     file_type = 1;
   else

open_key() returns INVALID_HANDLE_VALUE and EACCESS also if an upper
level key cannot be opened. The exists() function returns 1
(virt_directory) then, it should return 0 (virt_none).

Christian




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