[PATCH 04/39] mm/vma: ensure mmap_prepare doesn't set actions on a mergeable vma
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Date: 2026-09-08 20:04:22
Also in:
bpf, dri-devel, fuse-devel, kvm, kvm-riscv, kvmarm, linux-arch, linux-doc, linux-fbdev, linux-fsdevel, linux-mm, linux-perf-users, linux-rdma, linux-s390, linux-scsi, linux-sound, linux-usb, linuxppc-dev, lkml, selinux, sparclinux
Subsystem:
memory management, memory mapping, the rest · Maintainers:
Andrew Morton, Liam R. Howlett, Lorenzo Stoakes, Linus Torvalds
When a user requests an mmap_action be performed in mmap_prepare, this involves populating the VMA range with data. However, if the VMA is mergeable, it might then mistakenly be merged with another VMA without having populated the range. Every mmap action currently available sets VMA flags such that the VMA cannot be merged. However, to ensure that no future mmap action falls foul of this, assert that this is the case upon mmap_prepare validation. Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org> --- mm/vma.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/mm/vma.c b/mm/vma.c
index a24f04428580..9e45fc83f74c 100644
--- a/mm/vma.c
+++ b/mm/vma.c@@ -2794,6 +2794,15 @@ static int mmap_validate(unsigned long prev_start, int mmap_prepare_validate(const struct vm_area_desc *prev_desc, const struct vm_area_desc *desc) { + /* + * It is not valid to execute mmap actions for VMAs which can be merged, + * as any such merge would leave portions of the mapping incorrectly + * unmapped. + */ + if (vma_flags_can_merge(&desc->vma_flags) && + WARN_ON_ONCE(desc->action.type != MMAP_NOTHING)) + return -EINVAL; + return mmap_validate(prev_desc->start, desc->start, &prev_desc->vma_flags, &desc->vma_flags); }
--
2.55.0