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Date: Thu, 15 Jul 2021 14:17:30 +0200
From: Jan Kara <jack@...e.cz>
To: Ira Weiny <ira.weiny@...el.com>
Cc: Javier Pello <javier.pello@...c.es>, Jan Kara <jack@...e.cz>,
Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] fs/ext2: Avoid page_address on pages returned by
ext2_get_page
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@...c.es>
> >
> > 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@...el.com>
Thanks for the patch and the review. I'de added the patch to my tree.
Honza
>
> > Signed-off-by: Javier Pello <javier.pello@...c.es>
> > 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@...e.com>
SUSE Labs, CR
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