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Bug 193370 - ainit creates semaphores and shmem with wrong permissions
ainit creates semaphores and shmem with wrong permissions
Product: Fedora
Classification: Fedora
Component: alsa-lib (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Martin Stransky
Depends On:
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Reported: 2006-05-27 17:10 EDT by Roberto Ragusa
Modified: 2007-11-30 17:11 EST (History)
0 users

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2006-07-21 04:59:24 EDT
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Description Roberto Ragusa 2006-05-27 17:10:55 EDT
Description of problem:

The ipc_perm parameter in dmix.template and dsnoop_template
has no effect, because ainit always uses 0600 as permission.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. Modify /etc/alsa/dmix.template, changing for example
     ipc_perm 0600
     ipc_perm 0666
2. ainit <name_of_the_user> start
3. ipcs -a
Actual results:

The shared memory segments and the semaphore arrays have
been created with permission 0600 and not 0666.

Expected results:

Permission should be respected.

Additional info:

I want to mix audio from many users, so I tried to set ipc_perm
to 0666 in /etc/alsa/dmix.template and /etc/alsa/dsnoop.template
(in addition to 0666 permission on the devices).
This doesn't work well, because when ainit creates
/etc/alsa/dmix.conf and /etc/alsa/dsnoop.conf it allocates
ipc_key and ipc_semaphore using an hardcoded permission of 0600.
The generated *.conf files do contain the "ipc_perm 0666" line,
but the keys and the semaphore have already been incorrectly created.

The problem is here (hardcoded 0600):

/* Checking if IPC key/semaphore already exist
int check_ipc_key(key_t key)
  int shm_id = shmget(key, 1, IPC_CREAT | IPC_EXCL | 0600);
  return (shm_id >= 0);

int check_ipc_semaphore(key_t key)
  int shm_id = semget(key, 1, IPC_CREAT | IPC_EXCL | 0600);
  return (shm_id >= 0);
Comment 1 Martin Stransky 2006-07-21 04:59:24 EDT
fixed in rawhide, I removed all ainit stuffs, they're not needed any more in the
latest upstream.

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