Messages in this thread | | | Date | Thu, 11 Oct 2007 10:19:56 +0200 | From | Nadia Derbey <> | Subject | Re: [RFC][PATCH -mm] IPC: fix error checking in all new xxx_lock() functions |
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Pierre Peiffer wrote: > In the new implementation of the [sem|shm|msg]_lock[_check]() routines, > we use the return value of ipc_lock() in container_of() without any check. > But ipc_lock may return a errcode. The use of this errcode in container_of() > may alter this errcode, and we don't want this. > > Today, there is no problem because the member used in these container_of() > is the first member of its container (offset == 0), the errcode isn't changed > then. But in the general case, we can't count on this assumption and this > may lead later to a real bug if we don't correct this. > > In fact, the proposed solution is simple and correct. But it has the drawback > of adding one more check ('if' statement) in the chain: we do a first check in > ipc_lock(), now in xxx_lock() and then one later in the caller of xxx_lock() > That's why I send this as RFC, may be another approach could be considered. >
This is really what disturbs me this solution: the same check will be done several times. But is true that we have to do something. So why not simply adding a BIG COMMENT before the msg_queue, sem_array and shmid_ds stating that the kern_ipc_perm should stay at the beinnign of the structure?
Will try to look for another solution.
Regards, Nadia
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