Commit e40cfce6 authored Sep 16, 2012 by Oleg Nesterov

uprobes: Restrict valid_vma(false) to skip VM_SHARED vmas



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>

parent 78a32054

kernel/events/uprobes.c

+4 −9

Original line number	Diff line number	Diff line
		@@ -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)

Admin message