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Mon, 30 Mar 2026 01:40:13 -0700 (PDT) Received: from SH-PF5NDYD6.Hygon.cn ([112.64.138.194]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b24264286fsm75729845ad.14.2026.03.30.01.40.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 01:40:12 -0700 (PDT) From: Ke Zhao Date: Mon, 30 Mar 2026 16:36:19 +0800 Subject: [PATCH] mm, KMSAN: Add missing shadow memory initialization in special allocation paths Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260330-fix-kmsan-v1-1-e9c672a4b9eb@gmail.com> X-B4-Tracking: v=1; b=H4sIAAI2ymkC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzMDYyNT3bTMCt3s3OLEPN1UI0vDNHNTo0RLE0sloPqColSgJNis6NjaWgD yeY6AWwAAAA== To: Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , John Hubbard , Brendan Jackman , Johannes Weiner , Zi Yan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ke Zhao , syzbot+2aee6839a252e612ce34@syzkaller.appspotmail.com X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1774860009; l=1950; i=ke.zhao.kernel@gmail.com; s=20260325; h=from:subject:message-id; bh=9oBf2FE0Up2qxJXhKO76c63IMdnX+zedgNnn+/XRlsc=; b=9erKfsLmwyKeLrVGjXonYf6sVKX9oGLOHsVfVYEQFL8p6RGCIvyhIleKcqS8PrEc58SD485uJ LqG1gtAw6KoBcAEClsigLao/TD9u+3VPs5lkPBl5CmeiMS6zv9Wuow+ X-Developer-Key: i=ke.zhao.kernel@gmail.com; a=ed25519; pk=t0w8oqPLx0EV3Oq8QAh4yW+oVJxOabTNVP1OEbkzWIA= Some page allocation paths that call post_alloc_hook() but skip kmsan_alloc_page(), leaving stale KMSAN shadow on allocated pages. Fix this by explicitly calling kmsan_alloc_page() after they successfully get new pages. Reported-by: syzbot+2aee6839a252e612ce34@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D2aee6839a252e612ce34 Signed-off-by: Ke Zhao --- mm/page_alloc.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2d4b6f1a554e..6435e8708ef4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5189,6 +5189,10 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int= preferred_nid, =20 prep_new_page(page, 0, gfp, 0); set_page_refcounted(page); + + trace_mm_page_alloc(page, 0, gfp, ac.migratetype); + kmsan_alloc_page(page, 0, gfp); + page_array[nr_populated++] =3D page; } =20 @@ -6911,6 +6915,12 @@ static void split_free_frozen_pages(struct list_head= *list, gfp_t gfp_mask) int i; =20 post_alloc_hook(page, order, gfp_mask); + /* + * Initialize KMSAN state right after post_alloc_hook(). + * This prepares the pages for subsequent outer callers + * that might free sub-pages after the split. + */ + kmsan_alloc_page(page, order, gfp_mask); if (!order) continue; =20 @@ -7117,6 +7127,9 @@ int alloc_contig_frozen_range_noprof(unsigned long st= art, unsigned long end, =20 check_new_pages(head, order); prep_new_page(head, order, gfp_mask, 0); + + trace_mm_page_alloc(page, order, gfp_mask, get_pageblock_migratetype(pag= e)); + kmsan_alloc_page(page, order, gfp_mask); } else { ret =3D -EINVAL; WARN(true, "PFN range: requested [%lu, %lu), allocated [%lu, %lu)\n", --- base-commit: bbeb83d3182abe0d245318e274e8531e5dd7a948 change-id: 20260325-fix-kmsan-e291f752a949 Best regards, --=20 Ke Zhao