linux-kernel - [PATCH] mm/madvise: elevate page refcount while isolating in process

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <1639571019-30043-1-git-send-email-quic_charante@quicinc.com>
Date:   Wed, 15 Dec 2021 17:53:39 +0530
From:   Charan Teja Reddy <quic_charante@...cinc.com>
To:     <akpm@...ux-foundation.org>, <minchan@...nel.org>,
        <surenb@...gle.com>, <vbabka@...e.cz>, <rientjes@...gle.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Charan Teja Reddy <quic_charante@...cinc.com>
Subject: [PATCH] mm/madvise: elevate page refcount while isolating in process_madvise()

The documentation of isolate_lru_page() says that, "it must be called
with an elevated refcount on the page", which is not followed while
isolating pages in process_madvise() system call with advise
MADV_PAGEOUT. Fix it.

Signed-off-by: Charan Teja Reddy <quic_charante@...cinc.com>
---
 mm/madvise.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 0734db8..4c4a8e9 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -317,6 +317,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 	pte_t *orig_pte, *pte, ptent;
 	spinlock_t *ptl;
 	struct page *page = NULL;
+	int ret;
 	LIST_HEAD(page_list);
 
 	if (fatal_signal_pending(current))
@@ -373,12 +374,15 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 		ClearPageReferenced(page);
 		test_and_clear_page_young(page);
 		if (pageout) {
-			if (!isolate_lru_page(page)) {
+			get_page(page);
+			ret = isolate_lru_page(page);
+			if (!ret) {
 				if (PageUnevictable(page))
 					putback_lru_page(page);
 				else
 					list_add(&page->lru, &page_list);
 			}
+			put_page(page);
 		} else
 			deactivate_page(page);
 huge_unlock:
@@ -459,12 +463,15 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 		ClearPageReferenced(page);
 		test_and_clear_page_young(page);
 		if (pageout) {
-			if (!isolate_lru_page(page)) {
+			get_page(page);
+			ret = isolate_lru_page(page);
+			if (!ret) {
 				if (PageUnevictable(page))
 					putback_lru_page(page);
 				else
 					list_add(&page->lru, &page_list);
 			}
+			put_page(page);
 		} else
 			deactivate_page(page);
 	}
-- 
2.7.4