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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 <surenb@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Suren Baghdasaryan 2023-07-08 12:12:10 -07:00 committed by Linus Torvalds
parent 7fcd473a64
commit c137381f71
1 changed files with 4 additions and 0 deletions
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4
mm/mmap.c
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@ -1977,6 +1977,8 @@ 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
@ -2064,6 +2066,8 @@ 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