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authorVasily Averin <vvs@virtuozzo.com>2020-05-13 17:50:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-05-14 10:00:35 -0700
commit5e698222c70257d13ae0816720dde57c56f81e15 (patch)
treef53bdc8e4d856267d5a892720982d251ba8c514b
parentd1564926066115fb47ca06b2b9d23ed506ca9608 (diff)
downloadlwn-5e698222c70257d13ae0816720dde57c56f81e15.tar.gz
lwn-5e698222c70257d13ae0816720dde57c56f81e15.zip
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. Fixes: 89163f93c6f9 ("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>
-rw-r--r--ipc/util.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/ipc/util.c b/ipc/util.c
index 7acccfded7cb..cfa0045e748d 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -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)