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SubjectRe: [PATCH] prctl: Get private anonymous memory region name
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On 11/25/23 23:56, Oleg Nesterov wrote:
> On 11/25, Rong Tao wrote:
>> +static int prctl_get_vma(unsigned long opt, unsigned long addr,
>> + unsigned long buf, unsigned long arg)
>> +{
>> + struct mm_struct *mm = current->mm;
>> + const char __user *u_buf;
>> + int error;
>> +
>> + switch (opt) {
>> + case PR_GET_VMA_ANON_NAME:
>> + const struct anon_vma_name *anon_name = NULL;
>> +
>> + u_buf = (const char __user *)buf;
>> + error = 0;
>> +
>> + mmap_read_lock(mm);
>> + anon_name = madvise_get_anon_name(mm, addr);
>> + if (!anon_name) {
>> + mmap_read_unlock(mm);
>> + error = -EFAULT;
> may be another error code makes sense to distinguish this case from
> the copy_to_user() failure?
>
>> + break;
>> + }
>> +
>> + if (copy_to_user((char __user *)u_buf, anon_name->name,
>> + strlen(anon_name->name) + 1))
>> + error = -EFAULT;
> and I guess you can simplify this code a bit,
>
> anon_name = madvise_get_anon_name(...);
> if (!anon_name || copy_to_user(...))
> error = -EFAULT;
Thanks a lot, I just modify the code, please review.
>
> mmap_read_unlock(mm);
> anon_vma_name_put(anon_name); // safe if anon_name == NULL;
>
>> +const struct anon_vma_name *madvise_get_anon_name(struct mm_struct *mm,
>> + unsigned long start)
>> +{
>> + struct vm_area_struct *vma;
>> + struct anon_vma_name *anon_name;
>> +
>> + vma = find_vma(mm, start);
>> + if (vma) {
>> + anon_name = anon_vma_name(vma);
>> + if (anon_name) {
>> + anon_vma_name_get(anon_name);
>> + return anon_name;
>> + }
>> + }
>> +
>> + return NULL;
> Again, afaics this can be simplified,
>
> struct anon_vma_name *anon_name = NULL;
>
> vma = find_vma(mm, start);
> if (vma) {
> anon_name = anon_vma_name(vma);
> anon_vma_name_get(anon_name);
> }
>
> return anon_name;
>
> Oleg.
Thanks again.

Rong Tao

>

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