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([121.185.186.233]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-76e7d4f7cf7sm9891448b3a.69.2025.08.21.22.59.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Aug 2025 22:59:26 -0700 (PDT) From: Jeongjun Park To: muchun.song@linux.dev, osalvador@suse.de, david@redhat.com, akpm@linux-foundation.org Cc: leitao@debian.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+417aeb05fd190f3a6da9@syzkaller.appspotmail.com, Jeongjun Park Subject: [PATCH] mm/hugetlb: add missing hugetlb_lock in __unmap_hugepage_range() Date: Fri, 22 Aug 2025 14:58:57 +0900 Message-Id: <20250822055857.1142454-1-aha310510@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When restoring a reservation for an anonymous page, we need to check to freeing a surplus. However, __unmap_hugepage_range() causes data race because it reads h->surplus_huge_pages without the protection of hugetlb_lock. Therefore, we need to add missing hugetlb_lock. Reported-by: syzbot+417aeb05fd190f3a6da9@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D417aeb05fd190f3a6da9 Fixes: df7a6d1f6405 ("mm/hugetlb: restore the reservation if needed") Signed-off-by: Jeongjun Park Reviewed-by: Sidhartha Kumar --- mm/hugetlb.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 753f99b4c718..e8d95a314df2 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5951,6 +5951,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, s= truct vm_area_struct *vma, * If there we are freeing a surplus, do not set the restore * reservation bit. */ + spin_lock_irq(&hugetlb_lock); + if (!h->surplus_huge_pages && __vma_private_lock(vma) && folio_test_anon(folio)) { folio_set_hugetlb_restore_reserve(folio); @@ -5958,6 +5960,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, s= truct vm_area_struct *vma, adjust_reservation =3D true; } =20 + spin_unlock_irq(&hugetlb_lock); spin_unlock(ptl); =20 /* --