Re: [PATCH -next] uprobes: fix two zero old_folio bugs in __replace_page()
From: Oleg Nesterov <oleg@redhat.com>
Date: 2025-02-17 16:13:03
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Can't comment, my understanding of mm/ is not enough these days. Just one question... On 02/17, Tong Tiangen wrote:
Fixes: 7396fa818d62 ("uprobes/core: Make background page replacement logic account for rss_stat counters")
Fixes: 2b1444983508 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints")Are you sure this logic was wrong from the very beginning? Just curious. Oleg.
quoted hunk ↗ jump to hunk
Signed-off-by: Tong Tiangen <redacted> --- kernel/events/uprobes.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 46ddf3a2334d..ff5694acfa68 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c@@ -213,7 +213,8 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, dec_mm_counter(mm, MM_ANONPAGES); if (!folio_test_anon(old_folio)) { - dec_mm_counter(mm, mm_counter_file(old_folio)); + if (!is_zero_folio(old_folio)) + dec_mm_counter(mm, mm_counter_file(old_folio)); inc_mm_counter(mm, MM_ANONPAGES); }@@ -227,7 +228,8 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, if (!folio_mapped(old_folio)) folio_free_swap(old_folio); page_vma_mapped_walk_done(&pvmw); - folio_put(old_folio); + if (!is_zero_folio(old_folio)) + folio_put(old_folio); err = 0; unlock:-- 2.25.1