From 2c12ea498f349207c28840c0ed9654321aab7720 Mon Sep 17 00:00:00 2001 From: Doug Ledford Date: Thu, 31 May 2012 16:26:36 -0700 Subject: [PATCH] ipc/mqueue: correct mq_attr_ok test 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). 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. [akpm@linux-foundation.org: add a local to simplify overflow-checking expression] Signed-off-by: Doug Ledford Cc: Stephen Rothwell Cc: Manfred Spraul Acked-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/mqueue.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/ipc/mqueue.c b/ipc/mqueue.c index 3c72a05..076399c 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -676,6 +676,9 @@ static void remove_notification(struct mqueue_inode_info *info) 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 +693,11 @@ 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 *))) < - (unsigned long)(attr->mq_maxmsg * attr->mq_msgsize)) + 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); + total_size = attr->mq_maxmsg * attr->mq_msgsize; + if (total_size + mq_treesize < total_size) return 0; return 1; } -- 2.7.4