Messages in this thread | | | Date | Tue, 25 Sep 2012 14:35:09 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH 3/3] uprobes: Restrict valid_vma(false) to skip VM_SHARED |
| |
* Oleg Nesterov <oleg@redhat.com> [2012-09-16 19:52:48]:
> valid_vma(false) ignores ->vm_flags, this is not actually right. > We should never try to write into MAP_SHARED mapping, this can > confuse an apllication which actually writes to ->vm_file.
Agree,
> > With this patch valid_vma(false) ignores VM_WRITE only but checks > other (immutable) bits checked by valid_vma(true).
Yes, checking for other immutable flags other than VM_WRITE is good.
> This can also > speedup uprobe_munmap() and uprobe_unregister(). >
I didnt get how it speeds up uprobe_munmap() and uprobe_unregister()?
> Note: even after this patch _unregister can confuse the probed > application if it does mprotect(PROT_WRITE) after _register and > installs "int3", but this is hardly possible to avoid and this > doesn't differ from gdb case. >
Again I didnt quite understand how unregister can confuse the probed application.
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
The changes look good.
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> --- > kernel/events/uprobes.c | 13 ++++--------- > 1 files changed, 4 insertions(+), 9 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index b9b50dd..78364a2 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -100,17 +100,12 @@ struct uprobe { > */ > static bool valid_vma(struct vm_area_struct *vma, bool is_register) > { > - if (!vma->vm_file) > - return false; > - > - if (!is_register) > - return true; > + vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED; > > - if ((vma->vm_flags & (VM_HUGETLB | VM_WRITE | VM_MAYEXEC | VM_SHARED)) > - == VM_MAYEXEC) > - return true; > + if (is_register) > + flags |= VM_WRITE; > > - return false; > + return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC; > } > > static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset) > -- > 1.5.5.1 >
| |