Re: [PATCH v2] fs/ext2: Avoid page_address on pages returned by ext2_get_page

[Jan Kara]

On Wed 14-07-21 10:07:46, Ira Weiny wrote:
> On Wed, Jul 14, 2021 at 06:54:48PM +0200, Javier Pello wrote:
> > From: Javier Pello <javier.pello@xxxxxxx>
> > 
> > Commit 782b76d7abdf02b12c46ed6f1e9bf715569027f7 ("fs/ext2: Replace
> > kmap() with kmap_local_page()") replaced the kmap/kunmap calls in
> > ext2_get_page/ext2_put_page with kmap_local_page/kunmap_local for
> > efficiency reasons. As a necessary side change, the commit also
> > made ext2_get_page (and ext2_find_entry and ext2_dotdot) return
> > the mapping address along with the page itself, as it is required
> > for kunmap_local, and converted uses of page_address on such pages
> > to use the newly returned address instead. However, uses of
> > page_address on such pages were missed in ext2_check_page and
> > ext2_delete_entry, which triggers oopses if kmap_local_page happens
> > to return an address from high memory. Fix this now by converting
> > the remaining uses of page_address to use the right address, as
> > returned by kmap_local_page.
> > 
> 
> Again thanks for catching this!
> 
> Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>

Thanks for the patch and the review. I'de added the patch to my tree.

								Honza

> 
> > Signed-off-by: Javier Pello <javier.pello@xxxxxxx>
> > Fixes: 782b76d7abdf ("fs/ext2: Replace kmap() with kmap_local_page()")
> > ---
> > 
> > v2: Use char * for the new parameter to ext2_delete_entry.
> > 
> >  fs/ext2/dir.c   | 12 ++++++------
> >  fs/ext2/ext2.h  |  3 ++-
> >  fs/ext2/namei.c |  4 ++--
> >  3 files changed, 10 insertions(+), 9 deletions(-)
> > 
> > diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
> > index 14292dba..2c2f179b 100644
> > --- a/fs/ext2/dir.c
> > +++ b/fs/ext2/dir.c
> > @@ -106,12 +106,11 @@ static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
> >  	return err;
> >  }
> >  
> > -static bool ext2_check_page(struct page *page, int quiet)
> > +static bool ext2_check_page(struct page *page, int quiet, char *kaddr)
> >  {
> >  	struct inode *dir = page->mapping->host;
> >  	struct super_block *sb = dir->i_sb;
> >  	unsigned chunk_size = ext2_chunk_size(dir);
> > -	char *kaddr = page_address(page);
> >  	u32 max_inumber = le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count);
> >  	unsigned offs, rec_len;
> >  	unsigned limit = PAGE_SIZE;
> > @@ -205,7 +204,8 @@ static struct page * ext2_get_page(struct inode *dir, unsigned long n,
> >  	if (!IS_ERR(page)) {
> >  		*page_addr = kmap_local_page(page);
> >  		if (unlikely(!PageChecked(page))) {
> > -			if (PageError(page) || !ext2_check_page(page, quiet))
> > +			if (PageError(page) || !ext2_check_page(page, quiet,
> > +								*page_addr))
> >  				goto fail;
> >  		}
> >  	}
> > @@ -584,10 +584,10 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
> >   * ext2_delete_entry deletes a directory entry by merging it with the
> >   * previous entry. Page is up-to-date.
> >   */
> > -int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
> > +int ext2_delete_entry (struct ext2_dir_entry_2 *dir, struct page *page,
> > +			char *kaddr)
> >  {
> >  	struct inode *inode = page->mapping->host;
> > -	char *kaddr = page_address(page);
> >  	unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
> >  	unsigned to = ((char *)dir - kaddr) +
> >  				ext2_rec_len_from_disk(dir->rec_len);
> > @@ -607,7 +607,7 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
> >  		de = ext2_next_entry(de);
> >  	}
> >  	if (pde)
> > -		from = (char*)pde - (char*)page_address(page);
> > +		from = (char *)pde - kaddr;
> >  	pos = page_offset(page) + from;
> >  	lock_page(page);
> >  	err = ext2_prepare_chunk(page, pos, to - from);
> > diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
> > index b0a69482..e512630c 100644
> > --- a/fs/ext2/ext2.h
> > +++ b/fs/ext2/ext2.h
> > @@ -740,7 +740,8 @@ extern int ext2_inode_by_name(struct inode *dir,
> >  extern int ext2_make_empty(struct inode *, struct inode *);
> >  extern struct ext2_dir_entry_2 *ext2_find_entry(struct inode *, const struct qstr *,
> >  						struct page **, void **res_page_addr);
> > -extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
> > +extern int ext2_delete_entry(struct ext2_dir_entry_2 *dir, struct page *page,
> > +			     char *kaddr);
> >  extern int ext2_empty_dir (struct inode *);
> >  extern struct ext2_dir_entry_2 *ext2_dotdot(struct inode *dir, struct page **p, void **pa);
> >  extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, void *,
> > diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
> > index 1f69b816..5f6b7560 100644
> > --- a/fs/ext2/namei.c
> > +++ b/fs/ext2/namei.c
> > @@ -293,7 +293,7 @@ static int ext2_unlink(struct inode * dir, struct dentry *dentry)
> >  		goto out;
> >  	}
> >  
> > -	err = ext2_delete_entry (de, page);
> > +	err = ext2_delete_entry (de, page, page_addr);
> >  	ext2_put_page(page, page_addr);
> >  	if (err)
> >  		goto out;
> > @@ -397,7 +397,7 @@ static int ext2_rename (struct user_namespace * mnt_userns,
> >  	old_inode->i_ctime = current_time(old_inode);
> >  	mark_inode_dirty(old_inode);
> >  
> > -	ext2_delete_entry(old_de, old_page);
> > +	ext2_delete_entry(old_de, old_page, old_page_addr);
> >  
> >  	if (dir_de) {
> >  		if (old_dir != new_dir)
> > -- 
> > 2.30.1
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR