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SubjectRe: [PATCH 1/3] uprobes: install_breakpoint() should fail if is_swbp_insn() == T
On 05/30, Peter Zijlstra wrote:
>
> register's vma
> iteration is very careful not to have the same vma twice,

Hmm. I am wondering if it is careful enough...

Just in case, I think your patch is great. But it seems to me
there is another problem.

__find_next_vma_info() checks tmpvi->mm == vma->vm_mm to detect the
already visited mm/vma. However, afaics this can be false positive?

The caller, register_for_each_vma(), does mmput() and after that
this memory can be freed and re-used as another mm_struct.

I'll recheck this, but perhaps we need something like below?

Oleg.

--- x/kernel/events/uprobes.c
+++ x/kernel/events/uprobes.c
@@ -851,7 +851,6 @@ static int register_for_each_vma(struct
list_del(&vi->probe_list);
kfree(vi);
up_write(&mm->mmap_sem);
- mmput(mm);
continue;
}
vaddr = vma_address(vma, uprobe->offset);
@@ -860,7 +859,6 @@ static int register_for_each_vma(struct
list_del(&vi->probe_list);
kfree(vi);
up_write(&mm->mmap_sem);
- mmput(mm);
continue;
}

@@ -870,7 +868,6 @@ static int register_for_each_vma(struct
remove_breakpoint(uprobe, mm, vi->vaddr);

up_write(&mm->mmap_sem);
- mmput(mm);
if (is_register) {
if (ret && ret == -EEXIST)
ret = 0;
@@ -881,6 +878,7 @@ static int register_for_each_vma(struct

list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) {
list_del(&vi->probe_list);
+ mmput(vi->mm)
kfree(vi);
}



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