From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Kenneth W" Date: Wed, 22 Feb 2006 02:53:32 +0000 Subject: RE: IA64 non-contiguous memory space bugs Message-Id: <200602220253.k1M2rWg10346@unix-os.sc.intel.com> List-Id: In-Reply-To: <20060222001359.GA23574@localhost.localdomain> References: <20060222001359.GA23574@localhost.localdomain> In-Reply-To: <20060222001359.GA23574@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: 'David Gibson' , linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org David Gibson wrote on Tuesday, February 21, 2006 4:14 PM > First bug (confirmed many months ago by Chris Wedgwood) - you can get > weird effects if you attempt to mmap() something into one of the > address space gaps. The ia64 outer wrapper for mmap2() tries to > prevent it, but doesn't do a good enough job, it's still possible > indirectly with shmat() and maybe mremap(). Basic trouble is that > most of the checks applied by the generic code assume that everything > between 0 and TASK_SIZE is valid. Ha ha ha. On ia64, the low level tlb fault handler (vhpt_miss and nested_dtlb_miss) checks that all unused address bits (between REGION_NUMBER and PGDIR_SHIFT) should be all zero. If they are not zero, it will fall into page fault handler and in there, ia64 should just send SEGV instead of happily hand over a page. Buggy buggy.... - Ken