Messages in this thread Patch in this message | | | Date | Tue, 1 May 2012 12:34:30 -0700 | From | Andrew Morton <> | Subject | Re: [Patch 2/4] ipc/mqueue: correct mq_attr_ok test |
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On Tue, 1 May 2012 13:50:53 -0400 Doug Ledford <dledford@redhat.com> wrote:
> While working on the other parts of the mqueue stuff, I noticed that > the calculation for overflow in mq_attr_ok didn't actually match > reality (this is especially true since my last patch which changed > how we account memory slightly).
Please cc Manfred on mqueue things? He still watches ;)
> In particular, we used to test for overflow using: > msgs * msgsize + msgs * sizeof(struct msg_msg *) > > That was never really correct because each message we allocate via > load_msg() is actually a struct msg_msg followed by the data for > the message (and if struct msg_msg + data exceeds PAGE_SIZE we end > up allocating struct msg_msgseg structs too, but accounting for them > would get really tedious, so let's ignore those...they're only a > pointer in size anyway). This patch updates the calculation to be > more accurate in regards to maximum possible memory consumption by the > mqueue. > > ... > > --- a/ipc/mqueue.c > +++ b/ipc/mqueue.c > > ... > > @@ -684,8 +686,11 @@ static int mq_attr_ok(struct ipc_namespace *ipc_ns, struct mq_attr *attr) > /* check for overflow */ > if (attr->mq_msgsize > ULONG_MAX/attr->mq_maxmsg) > return 0; > - if ((unsigned long)(attr->mq_maxmsg * (attr->mq_msgsize > - + sizeof (struct msg_msg *))) < > + mq_treesize = attr->mq_maxmsg * sizeof(struct msg_msg) + > + min_t(unsigned int, attr->mq_maxmsg, MQ_PRIO_MAX) * > + sizeof(struct posix_msg_tree_node); > + if ((unsigned long)(attr->mq_maxmsg * attr->mq_msgsize + > + mq_treesize) < > (unsigned long)(attr->mq_maxmsg * attr->mq_msgsize)) > return 0; > return 1;
That's a bit of a mouthful. Does this look OK?
--- a/ipc/mqueue.c~ipc-mqueue-correct-mq_attr_ok-test-fix +++ a/ipc/mqueue.c @@ -672,7 +672,8 @@ static void remove_notification(struct m static int mq_attr_ok(struct ipc_namespace *ipc_ns, struct mq_attr *attr) { int mq_treesize; - + unsigned long total_size; + if (attr->mq_maxmsg <= 0 || attr->mq_msgsize <= 0) return 0; if (capable(CAP_SYS_RESOURCE)) { @@ -690,9 +691,8 @@ static int mq_attr_ok(struct ipc_namespa mq_treesize = attr->mq_maxmsg * sizeof(struct msg_msg) + min_t(unsigned int, attr->mq_maxmsg, MQ_PRIO_MAX) * sizeof(struct posix_msg_tree_node); - if ((unsigned long)(attr->mq_maxmsg * attr->mq_msgsize + - mq_treesize) < - (unsigned long)(attr->mq_maxmsg * attr->mq_msgsize)) + total_size = attr->mq_maxmsg * attr->mq_msgsize; + if (total_size + mq_treesize < total_size) return 0; return 1; } _
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