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ipc/util.c: sysvipc_find_ipc() incorrectly updates position index

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Commit 89163f93c6 ("ipc/util.c: sysvipc_find_ipc() should increase
position index") is causing this bug (seen on 5.6.8):

   # ipcs -q

   ------ Message Queues --------
   key        msqid      owner      perms      used-bytes   messages

   # ipcmk -Q
   Message queue id: 0
   # ipcs -q

   ------ Message Queues --------
   key        msqid      owner      perms      used-bytes   messages
   0x82db8127 0          root       644        0            0

   # ipcmk -Q
   Message queue id: 1
   # ipcs -q

   ------ Message Queues --------
   key        msqid      owner      perms      used-bytes   messages
   0x82db8127 0          root       644        0            0
   0x76d1fb2a 1          root       644        0            0

   # ipcrm -q 0
   # ipcs -q

   ------ Message Queues --------
   key        msqid      owner      perms      used-bytes   messages
   0x76d1fb2a 1          root       644        0            0
   0x76d1fb2a 1          root       644        0            0

   # ipcmk -Q
   Message queue id: 2
   # ipcrm -q 2
   # ipcs -q

   ------ Message Queues --------
   key        msqid      owner      perms      used-bytes   messages
   0x76d1fb2a 1          root       644        0            0
   0x76d1fb2a 1          root       644        0            0

   # ipcmk -Q
   Message queue id: 3
   # ipcrm -q 1
   # ipcs -q

   ------ Message Queues --------
   key        msqid      owner      perms      used-bytes   messages
   0x7c982867 3          root       644        0            0
   0x7c982867 3          root       644        0            0
   0x7c982867 3          root       644        0            0
   0x7c982867 3          root       644        0            0

Whenever an IPC item with a low id is deleted, the items with higher ids
are duplicated, as if filling a hole.

new_pos should jump through hole of unused ids, pos can be updated
inside "for" cycle.

Fixes: 89163f93c6 ("ipc/util.c: sysvipc_find_ipc() should increase position index")
Reported-by: Andreas Schwab <schwab@suse.de>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Waiman Long <longman@redhat.com>
Cc: NeilBrown <neilb@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/4921fe9b-9385-a2b4-1dc4-1099be6d2e39@virtuozzo.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vasily Averin 2020-05-13 17:50:48 -07:00 committed by Linus Torvalds
parent d156492606
commit 5e698222c7
1 changed files with 6 additions and 6 deletions
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12
ipc/util.c
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@ -764,21 +764,21 @@ static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
total++;
}
*new_pos = pos + 1;
ipc = NULL;
if (total >= ids->in_use)
return NULL;
goto out;
for (; pos < ipc_mni; pos++) {
ipc = idr_find(&ids->ipcs_idr, pos);
if (ipc != NULL) {
rcu_read_lock();
ipc_lock_object(ipc);
return ipc;
break;
}
}
/* Out of range - return NULL to terminate iteration */
return NULL;
out:
*new_pos = pos + 1;
return ipc;
}
static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)