From: Vasily Averin vvs@virtuozzo.com 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@virtuozzo.com Fixes: 89163f93c6f9 ("ipc/util.c: sysvipc_find_ipc() should increase position index") Signed-off-by: Vasily Averin vvs@virtuozzo.com Reported-by: Andreas Schwab schwab@suse.de 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 Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
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) _