#40760 [NEW]: not honoring mode of shm_attach

[secker at careviewcom dot com]

From: secker at careviewcom dot com
Operating system: Debian 'Etch', kern 2.6.17-2-486
PHP version: 5.2.1
PHP Bug Type: Unknown/Other Function
Bug description: not honoring mode of shm_attach

Description:
------------
If I create a Shared memory segment using shm_attach with one user, and
set it as readable by all users, but only writable by the owner, then
other users cannot open the segment via shm_attach, they get permission
denied errors.

I would guess this is maybe because shm_attach can't open a segment as
read-only, and always tried to open it as rw?

Reproduce code:
---------------
run as someuser1:

<?php
$f = ftok('somefile', 'I');
$sh = shm_attach($f, 1024000, 0644);
?>

works if its not already created by another user...


run as someuser2:

<?php
$f = ftok('somefile', 'I');
$sh = shm_attach($f);
?>



Expected result:
----------------
what I would expect is that since I created it as 0644, other users should
be able to access it via read-only mode (which I can do if I open it using
shmop_open with the read-only flag instead).

Actual result:
--------------
second user gets "Permission Denied" php warning messages.

once again, I think this is mearly a result of shm_attach not actually
ever opening an shm as read-only, always read-write... but I might be
mistaken.


Thanks.

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[tony2001@php.net]

ID: 40760
Updated by: [email]tony2001@php.net[/email]
Reported By: secker at careviewcom dot com
-Status: Open
+Status: Bogus
Bug Type: Unknown/Other Function
Operating System: Debian 'Etch', kern 2.6.17-2-486
PHP Version: 5.2.1
New Comment:

>$sh = shm_attach($f);

[url]http://php.net/shm_attach[/url]
"..and the optional perm-bits perm (default: 0666)..."

>I would guess this is maybe because shm_attach can't open a segment
>as read-only, and always tried to open it as rw?

Exactly.
That's because by default it tries to open it in 0666 mode.
Specify 0644 and voila..


Previous Comments:
------------------------------------------------------------------------

[2007-03-08 17:41:31] secker at careviewcom dot com

Description:
------------
If I create a Shared memory segment using shm_attach with one user, and
set it as readable by all users, but only writable by the owner, then
other users cannot open the segment via shm_attach, they get permission
denied errors.

I would guess this is maybe because shm_attach can't open a segment as
read-only, and always tried to open it as rw?

Reproduce code:
---------------
run as someuser1:

<?php
$f = ftok('somefile', 'I');
$sh = shm_attach($f, 1024000, 0644);
?>

works if its not already created by another user...


run as someuser2:

<?php
$f = ftok('somefile', 'I');
$sh = shm_attach($f);
?>



Expected result:
----------------
what I would expect is that since I created it as 0644, other users
should be able to access it via read-only mode (which I can do if I
open it using shmop_open with the read-only flag instead).

Actual result:
--------------
second user gets "Permission Denied" php warning messages.

once again, I think this is mearly a result of shm_attach not actually
ever opening an shm as read-only, always read-write... but I might be
mistaken.


Thanks.


------------------------------------------------------------------------


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