Re: [PATCH v4 2/6] KVM: s390: pci: Fix memory accounting for pinned/unpinned pages

[Christian Borntraeger]

Am 22.07.26 um 19:06 schrieb Farhan Ali:
> The account_mem() and unaccount_mem() functions call get_uid() which
> increments the reference count of struct user_struct on every invocation.
> But we don't decrement the count by calling free_uid(). It also
> accounted/unaccounted the pages against the current->mm. But its possible
> the unaccount_mem() can be called from a different process context than the
> one that originally pinned the pages.
>
> Let's fix this by storing the pinning process user_struct and mm_struct
> when accounting for pinned pages, and subsequently free these resources
> when the pages are unpinned.
>
> Fixes: 3c5a1b6f0a18 ("KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding")
> Signed-off-by: Farhan Ali <alifm@xxxxxxxxxxxxx>

Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>


[..]
> -static inline int account_mem(unsigned long nr_pages)
> +static inline int account_mem(struct kvm_zdev *kzdev, unsigned long nr_pages)
>   {
>   	struct user_struct *user = get_uid(current_user());
>   	unsigned long page_limit, cur_pages, new_pages;
> +	int rc = 0;
>   
>   	page_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>   
>   	cur_pages = atomic_long_read(&user->locked_vm);
>   	do {
>   		new_pages = cur_pages + nr_pages;
> -		if (new_pages > page_limit)
> -			return -ENOMEM;
> +		if (new_pages > page_limit) {
> +			rc =  -ENOMEM;
                            ^^double space. I can fixup during apply.