From 05f7c7fe72fe3ac5b1cfdc3f4cfebf87f2f16442 Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Sat, 8 Jul 2023 12:12:10 -0700 Subject: [PATCH] UPSTREAM: mm: lock a vma before stack expansion With recent changes necessitating mmap_lock to be held for write while expanding a stack, per-VMA locks should follow the same rules and be write-locked to prevent page faults into the VMA being expanded. Add the necessary locking. Cc: stable@vger.kernel.org Signed-off-by: Suren Baghdasaryan Signed-off-by: Linus Torvalds (cherry picked from commit c137381f71aec755fbf47cd4e9bd4dce752c054c) Change-Id: I3e6a8c89c1fb7c0669e1232176bb04ea6b09bc0a Signed-off-by: Suren Baghdasaryan Signed-off-by: Greg Kroah-Hartman --- mm/mmap.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/mmap.c b/mm/mmap.c index a6857acce59f..bf2298de8a0f 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2029,6 +2029,8 @@ static int expand_upwards(struct vm_area_struct *vma, unsigned long address) return -ENOMEM; } + /* Lock the VMA before expanding to prevent concurrent page faults */ + vma_start_write(vma); /* * vma->vm_start/vm_end cannot change under us because the caller * is required to hold the mmap_lock in read mode. We need the @@ -2116,6 +2118,8 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address) return -ENOMEM; } + /* Lock the VMA before expanding to prevent concurrent page faults */ + vma_start_write(vma); /* * vma->vm_start/vm_end cannot change under us because the caller * is required to hold the mmap_lock in read mode. We need the