On Tue, 9 Jan 2024 08:28:06 -0800 Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> > - /* Protection change for the range is going to happen. */
> > - if (p.arg.flags & PM_SCAN_WP_MATCHING) {
> > - mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
> > - mm, p.arg.start, p.arg.end);
> > - mmu_notifier_invalidate_range_start(&range);
> > - }
> > -
> > for (walk_start = p.arg.start; walk_start < p.arg.end;
> > walk_start = p.arg.walk_end) {
> > long n_out;
>
> Nit, might be worth moving
>
> struct mmu_notifier_range range;
>
> inside the loop to guard against stale usage, but that's definitely optional.
Yes, I think that's nicer.
--- a/fs/proc/task_mmu.c~fs-proc-task_mmu-move-mmu-notification-mechanism-inside-mm-lock-fix
+++ a/fs/proc/task_mmu.c
@@ -2432,7 +2432,6 @@ static long pagemap_scan_flush_buffer(st
static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg)
{
- struct mmu_notifier_range range;
struct pagemap_scan_private p = {0};
unsigned long walk_start;
size_t n_ranges_out = 0;
@@ -2450,6 +2449,7 @@ static long do_pagemap_scan(struct mm_st
for (walk_start = p.arg.start; walk_start < p.arg.end;
walk_start = p.arg.walk_end) {
+ struct mmu_notifier_range range;
long n_out;
if (fatal_signal_pending(current)) {
_
I'm surprised this code doesn't generate a might-be-used-uninitialized
warning. I guess gcc got smarter.
