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RE: Issue about AIX


From: REIX, Tony
Subject: RE: Issue about AIX
Date: Thu, 7 Mar 2019 10:05:30 +0000

Hi Chet,


I've experimented on: AIX 6.1 TL9, AIX 7.1 TL3, AIX 7.2 TL0, AIX 7.2 TL2 .

They all show the issue (compared to bash as non-root and to ksh as root or 
non-root)

I have no AIX 5.3 machine. However, it's very old now.

Here below is the man of access() routine.


I found this issue when analyzing the failing tests of Git on AIX. When this 
bash issue on AIX is fixed, a set of Git tests are now OK.


The difference that I see between AIX and Linux is:

man access :

  AIX: The access subroutine indicates success for X_OK even if none of the 
execute file permission bits are set.

  Linux: If the calling process is privileged (i.e., its real UID is zero), 
then an X_OK check is successful for a regular file if execute permission is 
enabled for any of the file owner, group, or other.



Here is the test that I'm using:

# cat /tmp/TEST
rm /tmp/foo4
test -x /tmp/foo4 ; echo $?
touch /tmp/foo4
ls -l /tmp/foo4
test -x /tmp/foo4 ; echo $?
chmod +x /tmp/foo4
test -x /tmp/foo4 ; echo $?
rm /tmp/foo4


As root :

# ./bash_64 /tmp/TEST
rm: cannot remove '/tmp/foo4': No such file or directory
1
-rw-r--r-- 1 root system 0 Mar  7 10:40 /tmp/foo4
0
0

# ksh /tmp/TEST
rm: cannot remove '/tmp/foo4': No such file or directory
1
-rw-r--r-- 1 root system 0 Mar  7 10:41 /tmp/foo4
1
0

As non-root:

# ./bash_64 /tmp/TEST
rm: cannot remove '/tmp/foo4': No such file or directory
1
-rw-r--r-- 1 postgres postgres 0 Mar  7 10:49 /tmp/foo4
1
/opt/freeware/bin/chmod: line 1: /tmp/chmod: Permission denied
0



# man access

access, accessx, faccessx, accessxat, or faccessat Subroutine

Purpose

       Determines the accessibility of a file.

Library

       Standard C Library (libc.a)

Syntax

       #include  <unistd.h>

       int access (PathName,Mode)

       char *PathName;

       int Mode;

       int accessx (PathName, Mode, Who)

       char *PathName;

       int Mode, Who;

       int faccessx (FileDescriptor, Mode, Who)

       int FileDescriptor;

       int Mode, Who;

       int accessxat (DirFileDescriptor, PathName, Mode, Who)

       int DirFileDescriptor;

       char *PathName;

       int Mode, Who;

       int faccessat (DirFileDescriptor, PathName, Mode, Flag)

       int DirFileDescriptor;

       char *PathName;

       int Mode, Flag;

Description

       The access, accessx, accessxat, faccessat and faccessx subroutines 
determine the accessibility of a file system object. The accessx, accessxat, 
and faccessx subroutines allow
       the specification of a class of users or processes for whom access is to 
be checked.

       The caller must have search permission for all components of the 
PathName parameter.

       The accessxat subroutine is equivalent to the accessx subroutine, and 
the faccessat subroutine is equivalent to the access subroutine if the PathName 
parameter specifies an
       absolute path or if the DirFileDescriptor parameter is set to AT_FDCWD. 
The file accessibility is determined by the relative path to the directory that 
is associated with the
       DirFileDescriptor parameter instead of the current working directory. If 
the directory is accessed without the O_SEARCH open flag, the subroutine checks 
to determine whether
       directory searches are permitted by using the current permissions of the 
directory. If the directory is accessed with the O_SEARCH open flag, the 
subroutine does not perform

       the check.

Parameters

       Item
            Description
       PathName
            Specifies the path name of the file. If the PathName parameter 
refers to a symbolic link, the access subroutine returns information about the 
file pointed to by the
            symbolic link. If the DirFileDescriptor is specified and PathName 
is relative, then the DirFileDescriptor specifies the effective current working 
directory for the
            PathName.
       FileDescriptor
            Specifies the file descriptor of an open file.
       Mode
            Specifies the access modes to be checked. This parameter is a bit 
mask containing 0 or more of the following values, which are defined in the 
<sys/access.h> file:
              R_OK
                   Check read permission.
              W_OK
                   Check write permission.
              X_OK
                   Check execute or search permission.
              F_OK
                   Check the existence of a file.
            If none of these values are specified, the existence of a file is 
checked.
       Who
            Specifies the class of users for whom access is to be checked. This 
parameter must be one of the following values, which are defined in the 
<sys/access.h> file:
              ACC_SELF
                   Determines if access is permitted for the current process. 
The effective user and group IDs, the concurrent group set and the privilege of 
the current process are
                   used for the calculation.
              ACC_INVOKER
                   Determines if access is permitted for the invoker of the 
current process. The real user and group IDs, the concurrent group set, and the 
privilege of the invoker
                   are used for the calculation.

                   Note: The expression access (PathName, Mode) is equivalent 
to accessx (PathName, Mode, ACC_INVOKER).
              ACC_OTHERS
                   Determines if the specified access is permitted for any user 
other than the object owner. The Mode parameter must contain only one of the 
valid modes. Privilege is
                   not considered in the calculation.
              ACC_ALL
                   Determines if the specified access is permitted for all 
users. The Mode parameter must contain only one of the valid modes. Privilege 
is not considered in the
                   calculation .

                   Note: The accessx subroutine shows the same behavior by both 
the user and root with ACC_ALL.
       DirFileDescriptor
            Specifies the file descriptor of an open directory, which is used 
as the effective current working directory for the PathName argument. If the 
DirFileDescriptor parameter
            equals AT_FDCWD, the DirFileDescriptor parameter is ignored and the 
PathName argument specifies the complete file.
       Flag
            Specifies a bit field argument. If the Flag parameter equals 
AT_EACCESS, the effective user and group IDs are checked (ACC_SELF). If the 
Flag parameter is zero, the real
            IDs are checked (ACC_INVOKER).

Return Values

       If the requested access is permitted, the access, accessx, faccessx, 
accessxat, and faccessat subroutines return a value of 0. If the requested 
access is not permitted or the
       function call fails, a value of -1 is returned and the errno global 
variable is set to indicate the error.

       The access subroutine indicates success for X_OK even if none of the 
execute file permission bits are set.

Error Codes

       The access faccessat, accessx, and accessx subroutines fail if one or 
more of the following are true:

       Item
            Description
       EACCES
            Search permission is denied on a component of the PathName prefix.
       EFAULT
            The PathName parameter points to a location outside the allocated 
address space of the process.
       ELOOP
            Too many symbolic links were encountered in translating the 
PathName parameter.
       ENAMETOOLONG
            A component of the PathName parameter exceeded 255 characters or 
the entire PathName parameter exceeded 1022 characters.
       ENOENT
            A component of the PathName does not exist or the process has the 
disallow truncation attribute set.
       ENOENT
            The named file does not exist.
       ENOENT
            The PathName parameter was null.
       ENOENT
            A symbolic link was named, but the file to which it refers does not 
exist.
       ENOTDIR
            A component of the PathName is not a directory.
       ESTALE
            The process root or current directory is located in a virtual file 
system that has been unmounted.

       The faccessx subroutine fails if the following is true:
       Item
            Description
       EBADF
            The value of the FileDescriptor parameter is not valid.

       The access, accessx, and faccessx subroutines fail if one or more of the 
following is true:
       Item
            Description
       EACCES
            The file protection does not allow the requested access.
       ENOMEM
            Unable to allocate memory.
       EIO
            An I/O error occurred during the operation.
       EROFS
            Write access is requested for a file on a read-only file system.

       The accessxat and faccessat subroutines fail if one or more of the 
following settings are true:
       Item
            Description
       EBADF
            The PathName parameter does not specify an absolute path and the 
DirFileDescriptor argument is neither AT_FDCWD nor a valid file descriptor.
       EINVAL
            The value of the Flag parameter is not valid.
       ENOTDIR
            The PathName parameter is not an absolute path and 
DirFileDescriptor is a file descriptor but is not associated with a directory.

       If Network File System (NFS) is installed on your system, the accessx, 
accessxat, and faccessx subroutines can also fail if the following settings are 
true:
       Item
            Description
       ETIMEDOUT
            The connection timed out.
       ETXTBSY
            Write access is requested for a shared text file that is being 
executed.

       EINVAL
            The value of the Mode argument is invalid.




Cordialement,

Tony Reix

address@hidden

ATOS / Bull SAS
ATOS Expert
IBM Coop Architect & Technical Leader
Office : +33 (0) 4 76 29 72 67
1 rue de Provence - 38432 Échirolles - France
www.atos.net<https://mail.ad.bull.net/owa/redir.aspx?C=PvphmPvCZkGrAgHVnWGsdMcDKgzl_dEIsM6rX0g4u4v8V81YffzBGkWrtQeAXNovd3ttkJL8JIc.&URL=http%3a%2f%2fwww.atos.net%2f>
________________________________
De : Chet Ramey <address@hidden>
Envoyé : mercredi 6 mars 2019 22:11:58
À : REIX, Tony; address@hidden
Cc : address@hidden
Objet : Re: Issue about AIX

On 3/6/19 10:22 AM, REIX, Tony wrote:
> Hi,
>
>
> On AIX, like Solaris, when root, the test "test -x /tmp/AFile" returns true 
> even if the file is not executable.
>
> This issue is there for ages.
>
> Here attached is the patch for fixing it for v5.0 .

Thanks. Is this true for all versions of AIX?

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    
https://emea01.safelinks.protection.outlook.com/?url=http:%2F%2Ftiswww.cwru.edu%2F~chet%2F&amp;data=02%7C01%7Ctony.reix%40atos.net%7C23893ee88fd54a1afcf308d6a278799c%7C33440fc6b7c7412cbb730e70b0198d5a%7C0%7C0%7C636875035653705583&amp;sdata=IDJ93PZy7JkuNJt3pNwfzD%2BYk0TyFPnpEdaz1zuxlrA%3D&amp;reserved=0


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