From: Lorenzo Stoakes Date: Sun, 3 Aug 2025 11:11:22 +0000 (+0100) Subject: mm/mremap: catch invalid multi VMA moves earlier X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d5f416c7c36456676c2cf5ab98776db2e7601f27;p=users%2Fjedix%2Flinux-maple.git mm/mremap: catch invalid multi VMA moves earlier Previously, any attempt to solely move a VMA would require that the span specified reside within the span of that single VMA, with no gaps before or afterwards. After commit d23cb648e365 ("mm/mremap: permit mremap() move of multiple VMAs"), the multi VMA move permitted a gap to exist only after VMAs. This was done to provide maximum flexibility. However, We have consequently permitted this behaviour for the move of a single VMA including those not eligible for multi VMA move. The change introduced here means that we no longer permit non-eligible VMAs from being moved in this way. This is consistent, as it means all eligible VMA moves are treated the same, and all non-eligible moves are treated as they were before. This change does not break previous behaviour, which equally would have disallowed such a move (only in all cases). [lorenzo.stoakes@oracle.com: do not incorrectly reference invalid VMA in VM_WARN_ON_ONCE()] Link: https://lkml.kernel.org/r/b6dbda20-667e-4053-abae-8ed4fa84bb6c@lucifer.local Link: https://lkml.kernel.org/r/2b5aad5681573be85b5b8fac61399af6fb6b68b6.1754218667.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Cc: David Hildenbrand Cc: Jann Horn Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- diff --git a/mm/mremap.c b/mm/mremap.c index eb37d1668770..33b642076205 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -1820,10 +1820,11 @@ static unsigned long remap_move(struct vma_remap_struct *vrm) unsigned long start = vrm->addr; unsigned long end = vrm->addr + vrm->old_len; unsigned long new_addr = vrm->new_addr; - bool allowed = true, seen_vma = false; unsigned long target_addr = new_addr; unsigned long res = -EFAULT; unsigned long last_end; + bool seen_vma = false; + VMA_ITERATOR(vmi, current->mm, start); /* @@ -1836,9 +1837,7 @@ static unsigned long remap_move(struct vma_remap_struct *vrm) unsigned long addr = max(vma->vm_start, start); unsigned long len = min(end, vma->vm_end) - addr; unsigned long offset, res_vma; - - if (!allowed) - return -EFAULT; + bool multi_allowed; /* No gap permitted at the start of the range. */ if (!seen_vma && start < vma->vm_start) @@ -1867,9 +1866,15 @@ static unsigned long remap_move(struct vma_remap_struct *vrm) vrm->new_addr = target_addr + offset; vrm->old_len = vrm->new_len = len; - allowed = vma_multi_allowed(vma); - if (seen_vma && !allowed) - return -EFAULT; + multi_allowed = vma_multi_allowed(vma); + if (!multi_allowed) { + /* This is not the first VMA, abort immediately. */ + if (seen_vma) + return -EFAULT; + /* This is the first, but there are more, abort. */ + if (vma->vm_end < end) + return -EFAULT; + } res_vma = check_prep_vma(vrm); if (!res_vma) @@ -1878,7 +1883,7 @@ static unsigned long remap_move(struct vma_remap_struct *vrm) return res_vma; if (!seen_vma) { - VM_WARN_ON_ONCE(allowed && res_vma != new_addr); + VM_WARN_ON_ONCE(multi_allowed && res_vma != new_addr); res = res_vma; }