lkml.org 
[lkml]   [2012]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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
>



\
 
 \ /
  Last update: 2012-09-25 12:01    [W:0.074 / U:0.512 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site