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Sun, 12 Apr 2026 19:12:57 -0700 (PDT) Received: from SH-PF5NDYD6.Hygon.cn ([112.64.138.194]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35fb88b8730sm452023a91.4.2026.04.12.19.12.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Apr 2026 19:12:56 -0700 (PDT) From: Ke Zhao Date: Mon, 13 Apr 2026 10:12:40 +0800 Subject: [PATCH v2] 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: <20260413-fix-kmsan-v2-1-9cc8a53c36c7@gmail.com> X-B4-Tracking: v=1; b=H4sIABdR3GkC/03MTQ7CIBCG4as0sxYD07/gynuYLihO24kCBkyja bi72Lhw+c58eTZIFJkSnKoNIq2cOPgSeKjALsbPJPhaGlBiJ2tsxcQvcXPJeEGo1dS3aHSjoew fkcpzty5D6YXTM8T3Tq/qe/0ptfxTViWUIG27Hk0zahrPszN8P9rgYMg5fwAVOuE8ogAAAA== 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=1776046373; l=2266; i=ke.zhao.kernel@gmail.com; s=20260325; h=from:subject:message-id; bh=2E1kNHkocp6W6ZcbC2Z72lH7get3s1sxDhZSsK9tVHM=; b=2RYYLUeCe3WeGtfHt22cHlkJDNrqDJwFo5GvbAYJiQFnWSwll16I32oyjLxtk9wv/X5ct7Pjh VZ6mpbi5mzXBE7aa19CzhFSB9dzk3MiQ09HJ/AHUd8i2S6LwylmvYpm 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. Although there is no reproducer for this issue, this patch should be able to fix it 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 --- Changes in v2: - Use correct variable in alloc_contig_frozen_range_noprof()=20 - Remove trace_mm_page_alloc() in alloc_contig_frozen_range_noprof() since we does not trace it in the above branch, suggested by Vlastimil Ba= bka - Link to v1: https://lore.kernel.org/r/20260330-fix-kmsan-v1-1-e9c672a4b9e= b@gmail.com --- mm/page_alloc.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2d4b6f1a554e..e08678b9e9cd 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 +7127,8 @@ 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); + + kmsan_alloc_page(head, 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