From 61e012ab9a1cdec88ebcb55a061a09c4c6539058 Mon Sep 17 00:00:00 2001 From: "Lorenzo Stoakes (ARM)" Date: Tue, 13 Oct 2026 16:05:03 +0100 Subject: [PATCH] mm/mlock: clear VMA_LOCKED_MASK over mmap callback Currently there's a confusing mess around VMA_LOCKED_BIT and VMA_LOCKONFAULT_BIT. It is permitted for drivers to set any flags they like, with the VMA already possessing lock flags. This results in the absurd situation of a VMA possessing both VMA_SPECIAL_FLAGS and VMA_LOCKED_MASK flags, which is not permitted. This has resulted in mlock_vma_folio() having a very silly check for this scenario to work around it. There is no need for this - just clear the flags before invoking the hook and reinstate them afterwards if they are required. Nothing relies upon this being set during the mmap operation. mmap_prepare is unaffected by this so requires no fix. Link: https://lore.kernel.org/20261013-b4-mmap-prepare-vma-flag-sanify-v6-23-1aa3c9b139f9@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Reviewed-by: Zi Yan Acked-by: David Hildenbrand (Arm) Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Pedro Falcato Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Jonathan Corbet Cc: Greg Kroah-Hartman Cc: Dennis Dalessandro Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Paul Moore Cc: Stephen Smalley Cc: Jaroslav Kysela Cc: Takashi Iwai Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Andrii Nakryiko Cc: Eduard Zingerman Cc: Kumar Kartikeya Dwivedi Cc: Baolin Wang Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lance Yang Cc: Usama Arif Cc: Kiryl Shutsemau Cc: Doug Gilbert Cc: James Bottomley Cc: Martin K. Petersen Cc: Simona Vetter Cc: Helge Deller Cc: Sebastian Reichel Cc: John Hubbard Cc: Peter Xu Cc: Masami Hiramatsu Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: Arnaldo Carvalho de Melo Cc: Namhyung Kim Cc: Mark Rutland Cc: Rik van Riel Cc: Harry Yoo Cc: Juri Lelli Cc: Vincent Guittot Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Will Deacon Cc: Aneesh Kumar K.V Cc: Nicholas Piggin Cc: Arnd Bergmann Cc: Muchun Song Cc: Oscar Salvador Cc: Matthew Wilcox (Oracle) Cc: Jan Kara Cc: Marc Zyngier Cc: Oliver Upton Cc: Catalin Marinas Cc: Madhavan Srinivasan Cc: Anup Patel Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Albert Ou Cc: Christian Borntraeger Cc: Janosch Frank Cc: Claudio Imbrenda Cc: Alexander Gordeev Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Vasily Gorbik Cc: David S. Miller Cc: Andreas Larsson Cc: Al Viro Cc: Christian Brauner Cc: Matthew Brost Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Chris Li Cc: Kairui Song Cc: Kemeng Shi Cc: Nhat Pham Cc: Baoquan He Cc: Youngjun Park Cc: Johannes Weiner Cc: Qi Zheng Cc: Shakeel Butt Cc: Axel Rasmussen Cc: Yuanchu Xie Cc: Wei Xu Cc: Chengming Zhou Cc: Michal Hocko Cc: Miklos Szeredi Cc: Xu Xin Cc: Ihor Solodrai Cc: Bert Karwatzki --- mm/internal.h | 9 +-------- mm/vma.c | 15 +++++++++++++++ 2 files changed, 16 insertions(+), 8 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 8cef7593003c..93d8fa5ccabc 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -970,14 +970,7 @@ void mlock_folio(struct folio *folio); static inline void mlock_vma_folio(struct folio *folio, struct vm_area_struct *vma) { - /* - * The VM_SPECIAL check here serves two purposes. - * 1) VM_IO check prevents migration from double-counting during mlock. - * 2) Although mmap_region() and mlock_fixup() take care that VM_LOCKED - * is never left set on a VM_SPECIAL vma, there is an interval while - * file->f_op->mmap() is using vm_insert_page(s), when VM_LOCKED may - * still be set while VM_SPECIAL bits are added: so ignore it then. - */ + /* The VM_IO check prevents migration from double-counting during mlock. */ if (unlikely((vma->vm_flags & (VM_LOCKED|VM_SPECIAL)) == VM_LOCKED)) mlock_folio(folio); } diff --git a/mm/vma.c b/mm/vma.c index f334c87582d7..e422e06c7dfa 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -2625,6 +2625,11 @@ static int __mmap_new_file_vma(struct mmap_state *map, if (!map->vm_file->f_op->mmap) return 0; + /* + * Driver-specified flags may make the lock flags invalid, so clear + * VMA_LOCKED_MASK and reinstate it afterwards if appropriate. + */ + vma_clear_flags_mask(vma, VMA_LOCKED_MASK); error = mmap_file(vma->vm_file, vma); map->vm_file = vma->vm_file; @@ -2647,6 +2652,16 @@ static int __mmap_new_file_vma(struct mmap_state *map, return error; } + /* + * If the VMA is still eligible for mlock(), reinstate any original + * VMA_LOCKED_BIT and/or VMA_LOCKONFAULT_BIT flags. + */ + if (vma_supports_mlock(vma)) { + const vma_flags_t mask = vma_flags_and_mask(&map->vma_flags, VMA_LOCKED_MASK); + + vma_set_flags_mask(vma, mask); + } + map->vma_flags = vma->flags; return 0;