If some remap_pfn_range() calls succeeded before one failed, we still have buffer pages mapped into the userspace page tables when we drop the buffer reference with comedi_buf_map_put(bm). The userspace mappings are only cleaned up later in the mmap error path.
Fix it by explicitly flushing all mappings in our VMA on the comedi_mmap() error path.
See commit 79a61cc3fc04 ("mm: avoid leaving partial pfn mappings around in error case").
Cc: stable@vger.kernel.org Fixes: ed9eccbe8970 ("Staging: add comedi core") Signed-off-by: Jann Horn jannh@google.com --- Note: compile-tested only; I don't actually have comedi hardware, and I don't know anything about comedi. --- drivers/comedi/comedi_fops.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/comedi/comedi_fops.c b/drivers/comedi/comedi_fops.c index 1b481731df96..0e573df8646f 100644 --- a/drivers/comedi/comedi_fops.c +++ b/drivers/comedi/comedi_fops.c @@ -2414,6 +2414,15 @@ static int comedi_mmap(struct file *file, struct vm_area_struct *vma) vma->vm_private_data = bm;
vma->vm_ops->open(vma); + } else { + /* + * Leaving behind a partial mapping of a buffer we're about to + * drop is unsafe, see remap_pfn_range_notrack(). + * We need to zap the range here ourselves instead of relying + * on the automatic zapping in remap_pfn_range() because we call + * remap_pfn_range() in a loop. + */ + zap_page_range_single(vma, vma->vm_start, size, NULL); }
done:
--- base-commit: 6485cf5ea253d40d507cd71253c9568c5470cd27 change-id: 20241014-comedi-tlb-400246505961