Re: [PATCH] xfs: fix null pointer dereference when mapping is NULL

Brian Foster
2015-09-03T10:45:40Z

On Thu, Sep 03, 2015 at 10:57:40AM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> xfs_vm_set_page_dirty checks to see if mapping is NULL however
> before this unlikely check it already dereferenced mapping when
> initializing inode. Move the inode initialization after the mapping
> null check to avoid a potential null pointer dereference.
>
> Fixes: 22e757a49cf0 ("xfs: don't dirty buffers beyond EOF")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

> fs/xfs/xfs_aops.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index c77499b..d15ae85 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -1935,7 +1935,7 @@ xfs_vm_set_page_dirty(
> struct page *page)
> {
> struct address_space *mapping = page->mapping;
> - struct inode *inode = mapping->host;
> + struct inode *inode;
> loff_t end_offset;
> loff_t offset;
> int newly_dirty;
> @@ -1944,6 +1944,7 @@ xfs_vm_set_page_dirty(
> if (unlikely(!mapping))
> return !TestSetPageDirty(page);
>
> + inode = mapping->host;
> end_offset = i_size_read(inode);
> offset = page_offset(page);
>
> --
> 2.5.0
>
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