On Mon, Jun 02, 2014 at 06:17:59PM +0530, Vinayak Menon wrote: > An issue was observed when a userspace task exits. > The page which hits error here is the zero page. > In binder mmap, the whole of vma is not mapped. > On a task crash, when debuggerd reads the binder regions, > the unmapped areas fall to do_anonymous_page in handle_pte_fault, > due to the absence of a vm_fault handler. This results in > zero page being mapped. Later in zap_pte_range, vm_normal_page > returns zero page in the case of VM_MIXEDMAP and it results in the > error. > > BUG: Bad page map in process mediaserver pte:9dff379f pmd:9bfbd831 > page:c0ed8e60 count:1 mapcount:-1 mapping: (null) index:0x0 > page flags: 0x404(referenced|reserved) > addr:40c3f000 vm_flags:10220051 anon_vma: (null) mapping:d9fe0764 index:fd > vma->vm_ops->fault: (null) > vma->vm_file->f_op->mmap: binder_mmap+0x0/0x274 > CPU: 0 PID: 1463 Comm: mediaserver Tainted: G W 3.10.17+ #1 > [<c001549c>] (unwind_backtrace+0x0/0x11c) from [<c001200c>] (show_stack+0x10/0x14) > [<c001200c>] (show_stack+0x10/0x14) from [<c0103d78>] (print_bad_pte+0x158/0x190) > [<c0103d78>] (print_bad_pte+0x158/0x190) from [<c01055f0>] (unmap_single_vma+0x2e4/0x598) > [<c01055f0>] (unmap_single_vma+0x2e4/0x598) from [<c010618c>] (unmap_vmas+0x34/0x50) > [<c010618c>] (unmap_vmas+0x34/0x50) from [<c010a9e4>] (exit_mmap+0xc8/0x1e8) > [<c010a9e4>] (exit_mmap+0xc8/0x1e8) from [<c00520f0>] (mmput+0x54/0xd0) > [<c00520f0>] (mmput+0x54/0xd0) from [<c005972c>] (do_exit+0x360/0x990) > [<c005972c>] (do_exit+0x360/0x990) from [<c0059ef0>] (do_group_exit+0x84/0xc0) > [<c0059ef0>] (do_group_exit+0x84/0xc0) from [<c0066de0>] (get_signal_to_deliver+0x4d4/0x548) > [<c0066de0>] (get_signal_to_deliver+0x4d4/0x548) from [<c0011500>] (do_signal+0xa8/0x3b8) > > Add a vm_fault handler which returns VM_FAULT_SIGBUS, and prevents the > wrong fallback to do_anonymous_page. > > Signed-off-by: Vinayak Menon <vinayakm.list@xxxxxxxxx> > --- > drivers/staging/android/binder.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) Given a lack of objections, I'll go merge this... thanks, greg k-h _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
