From: Deepanshu Kartikey <kartikey406@gmail.com> stable inclusion from stable-v6.12.78 commit 08de46a75f91a6661bc1ce0a93614f4bc313c581 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14006 CVE: CVE-2026-23375 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit dd085fe9a8ebfc5d10314c60452db38d2b75e609 upstream. file_thp_enabled() incorrectly allows THP for files on anonymous inodes (e.g. guest_memfd and secretmem). These files are created via alloc_file_pseudo(), which does not call get_write_access() and leaves inode->i_writecount at 0. Combined with S_ISREG(inode->i_mode) being true, they appear as read-only regular files when CONFIG_READ_ONLY_THP_FOR_FS is enabled, making them eligible for THP collapse. Anonymous inodes can never pass the inode_is_open_for_write() check since their i_writecount is never incremented through the normal VFS open path. The right thing to do is to exclude them from THP eligibility altogether, since CONFIG_READ_ONLY_THP_FOR_FS was designed for real filesystem files (e.g. shared libraries), not for pseudo-filesystem inodes. For guest_memfd, this allows khugepaged and MADV_COLLAPSE to create large folios in the page cache via the collapse path, but the guest_memfd fault handler does not support large folios. This triggers WARN_ON_ONCE(folio_test_large(folio)) in kvm_gmem_fault_user_mapping(). For secretmem, collapse_file() tries to copy page contents through the direct map, but secretmem pages are removed from the direct map. This can result in a kernel crash: BUG: unable to handle page fault for address: ffff88810284d000 RIP: 0010:memcpy_orig+0x16/0x130 Call Trace: collapse_file hpage_collapse_scan_file madvise_collapse Secretmem is not affected by the crash on upstream as the memory failure recovery handles the failed copy gracefully, but it still triggers confusing false memory failure reports: Memory failure: 0x106d96f: recovery action for clean unevictable LRU page: Recovered Check IS_ANON_FILE(inode) in file_thp_enabled() to deny THP for all anonymous inode files. Link: https://syzkaller.appspot.com/bug?extid=33a04338019ac7e43a44 Link: https://lore.kernel.org/linux-mm/CAEvNRgHegcz3ro35ixkDw39ES8=U6rs6S7iP0gkR9e... Link: https://lkml.kernel.org/r/20260214001535.435626-1-kartikey406@gmail.com Fixes: 7fbb5e188248 ("mm: remove VM_EXEC requirement for THP eligibility") Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com> Reported-by: syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=33a04338019ac7e43a44 Tested-by: syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com Tested-by: Lance Yang <lance.yang@linux.dev> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Reviewed-by: Barry Song <baohua@kernel.org> Reviewed-by: Ackerley Tng <ackerleytng@google.com> Tested-by: Ackerley Tng <ackerleytng@google.com> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Fangrui Song <i@maskray.me> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> [ Ackerley: we don't have IS_ANON_FILE() yet. As guest_memfd does not apply yet, simply check for secretmem explicitly. ] Signed-off-by: Ackerley Tng <ackerleytng@google.com> Reviewed-by: David Hildenbrand (Arm) <david@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ze Zuo <zuoze1@huawei.com> --- include/linux/huge_mm.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 328b1fbb134c..86565da790e0 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -7,6 +7,7 @@ #include <linux/fs.h> /* only for vma_is_dax() */ #include <linux/kobject.h> +#include <linux/secretmem.h> vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf); int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, @@ -270,6 +271,9 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma) inode = vma->vm_file->f_inode; + if (secretmem_mapping(inode->i_mapping)) + return false; + return (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS)) && !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } -- 2.25.1