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([2405:201:682f:389d:8864:6033:780:138b]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-354b21fb723sm8577308a91.10.2026.02.08.19.36.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Feb 2026 19:36:13 -0800 (PST) From: Deepanshu Kartikey To: akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ackerleytng@google.com, seanjc@google.com, pbonzini@redhat.com, michael.roth@amd.com, vannapurve@google.com Cc: ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com, Deepanshu Kartikey Subject: [PATCH] mm: thp: Deny THP for guest_memfd and secretmem in file_thp_enabled() Date: Mon, 9 Feb 2026 09:05:58 +0530 Message-ID: <20260209033558.22943-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 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" file_thp_enabled() incorrectly returns true for guest_memfd and secretmem inodes because they appear as regular read-only files when CONFIG_READ_ONLY_THP_FOR_FS is enabled. This allows khugepaged and MADV_COLLAPSE to create large folios in the page cache, but their fault handlers do not support large folios. Add explicit checks for GUEST_MEMFD_MAGIC and SECRETMEM_MAGIC to reject these filesystems early in file_thp_enabled(). Reported-by: syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D33a04338019ac7e43a44 Tested-by: syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey --- mm/huge_memory.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 40cf59301c21..4f57c78b57dd 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -93,6 +93,9 @@ static inline bool file_thp_enabled(struct vm_area_struct= *vma) return false; =20 inode =3D file_inode(vma->vm_file); + if (inode->i_sb->s_magic =3D=3D GUEST_MEMFD_MAGIC || + inode->i_sb->s_magic =3D=3D SECRETMEM_MAGIC) + return false; =20 return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } --=20 2.43.0