From: Vasily Averin <vvs@xxxxxxxxxxxxx>
Subject: ipc/util.c: sysvipc_find_ipc() incorrectly updates position index
Commit 89163f93c6f9 ("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.
Link: http://lkml.kernel.org/r/4921fe9b-9385-a2b4-1dc4-1099be6d2e39@xxxxxxxxxxxxx
Fixes: 89163f93c6f9 ("ipc/util.c: sysvipc_find_ipc() should increase position index")
Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Reported-by: Andreas Schwab <schwab@xxxxxxx>
Acked-by: Waiman Long <longman@xxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/util.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- a/ipc/util.c~ipc-utilc-sysvipc_find_ipc-incorrectly-updates-position-index
+++ a/ipc/util.c
@@ -764,21 +764,21 @@ static struct kern_ipc_perm *sysvipc_fin
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)
_
