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>
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index a9de408..8d182bd 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -100,17 +100,12 @@
*/
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)
