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uprobes: Restrict valid_vma(false) to skip VM_SHARED vmas

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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.

With this patch valid_vma(false) ignores VM_WRITE only but checks
other (immutable) bits checked by valid_vma(true). This can also
speedup 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.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2012-09-16 19:31:39 +02:00
parent 78a320542e
commit e40cfce626
1 changed files with 4 additions and 9 deletions
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13
kernel/events/uprobes.c
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@ -100,17 +100,12 @@ struct uprobe {
*/
static bool valid_vma(struct vm_area_struct *vma, bool is_register)
{
if (!vma->vm_file)
return false;
vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED;
if (!is_register)
return true;
if (is_register)
flags |= VM_WRITE;
if ((vma->vm_flags & (VM_HUGETLB | VM_WRITE | VM_MAYEXEC | VM_SHARED))
== VM_MAYEXEC)
return true;
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)