[U-Boot] [PATCH v2 1/1] ubifs: avoid possible NULL dereference
Ladislav Michl
ladis at linux-mips.org
Tue Nov 21 22:40:52 UTC 2017
On Tue, Nov 21, 2017 at 11:06:35PM +0100, Heinrich Schuchardt wrote:
> If 'file' cannot be allocated due to an out of memory
> situation, NULL is dereferenced.
>
> Variables file and dentry are not needed at all.
> So let's eliminate them.
>
> When debugging this patch also avoids a misleading message
> "cannot find next direntry, error %d" in case of an out of
> memory situation. It is sufficent to write
> "%s: Error, no memory for malloc!\n" in this case.
>
> Reported-by: Ladislav Michl <ladis at linux-mips.org>
> Reported-by: Alex Sadovsky <nable.maininbox at googlemail.com>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
> ---
> fs/ubifs/ubifs.c | 25 ++-----------------------
> 1 file changed, 2 insertions(+), 23 deletions(-)
>
> diff --git a/fs/ubifs/ubifs.c b/fs/ubifs/ubifs.c
> index 4465523d5f..f3d190c763 100644
> --- a/fs/ubifs/ubifs.c
> +++ b/fs/ubifs/ubifs.c
> @@ -393,29 +393,18 @@ static int ubifs_finddir(struct super_block *sb, char *dirname,
> union ubifs_key key;
> struct ubifs_dent_node *dent;
> struct ubifs_info *c;
> - struct file *file;
> - struct dentry *dentry;
> struct inode *dir;
> int ret = 0;
>
> - file = kzalloc(sizeof(struct file), 0);
> - dentry = kzalloc(sizeof(struct dentry), 0);
> dir = kzalloc(sizeof(struct inode), 0);
> - if (!file || !dentry || !dir) {
> + if (!dir) {
> printf("%s: Error, no memory for malloc!\n", __func__);
> - err = -ENOMEM;
> - goto out;
> + goto out_free;
> }
>
> dir->i_sb = sb;
> - file->f_path.dentry = dentry;
> - file->f_path.dentry->d_parent = dentry;
> - file->f_path.dentry->d_inode = dir;
> - file->f_path.dentry->d_inode->i_ino = root_inum;
> c = sb->s_fs_info;
>
> - dbg_gen("dir ino %lu, f_pos %#llx", dir->i_ino, file->f_pos);
> -
> /* Find the first entry in TNC and save it */
> lowest_dent_key(c, &key, dir->i_ino);
> nm.name = NULL;
> @@ -425,9 +414,6 @@ static int ubifs_finddir(struct super_block *sb, char *dirname,
> goto out;
> }
>
> - file->f_pos = key_hash_flash(c, &dent->key);
> - file->private_data = dent;
> -
> while (1) {
> dbg_gen("feed '%s', ino %llu, new f_pos %#x",
> dent->name, (unsigned long long)le64_to_cpu(dent->inum),
> @@ -450,10 +436,6 @@ static int ubifs_finddir(struct super_block *sb, char *dirname,
> err = PTR_ERR(dent);
> goto out;
> }
> -
> - kfree(file->private_data);
We still need to kfree allocated 'dent' as it was previously allocated:
dent = kmalloc(zbr->len, GFP_NOFS);
in ubifs_tnc_next_ent.
> - file->f_pos = key_hash_flash(c, &dent->key);
> - file->private_data = dent;
> cond_resched();
> }
>
> @@ -462,9 +444,6 @@ out:
> dbg_gen("cannot find next direntry, error %d", err);
>
> out_free:
> - kfree(file->private_data);
Same as above.
> - free(file);
> - free(dentry);
> free(dir);
>
> return ret;
> --
> 2.11.0
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