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SubjectRe: [PATCH] mm: Add check for NULL for unlocked in fixup_user_fault
On Thu, 15 Dec 2022 12:39:30 +0300 Anastasia Belova <abelova@astralinux.ru> wrote:

> Check unlocked for NULL before dereference.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> ...
>
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1282,7 +1282,8 @@ int fixup_user_fault(struct mm_struct *mm,
> * could tell the callers so they do not need to unlock.
> */
> mmap_read_lock(mm);
> - *unlocked = true;
> + if (unlocked)
> + *unlocked = true;
> return 0;
> }

I don't believe this is necessary unless the caller passed
FAULT_FLAG_KILLABLE or FAULT_FLAG_ALLOW_RETRY in fault_flags.

It's clear as mud and some code comments would help.

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