[PATCH] ext4: Fix memleak in add_new_gdb

[PATCH] ext4: Fix memleak in add_new_gdb

[Dinghao Liu]

When ext4_journal_get_write_access() fails, we should release
n_group_desc, iloc.bh, dind and gdb_bh to prevent memleak.
It's the same when ext4_handle_dirty_super() fails, but we
don't need to release dind here because it has been released
before.

Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
---
 fs/ext4/resize.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index a50b51270ea9..efc0a022ca8e 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -843,8 +843,10 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
 
 	BUFFER_TRACE(dind, "get_write_access");
 	err = ext4_journal_get_write_access(handle, dind);
-	if (unlikely(err))
+	if (unlikely(err)) {
 		ext4_std_error(sb, err);
+		goto errout;
+	}
 
 	/* ext4_reserve_inode_write() gets a reference on the iloc */
 	err = ext4_reserve_inode_write(handle, inode, &iloc);
@@ -899,13 +901,17 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
 
 	le16_add_cpu(&es->s_reserved_gdt_blocks, -1);
 	err = ext4_handle_dirty_super(handle, sb);
-	if (err)
+	if (err) {
 		ext4_std_error(sb, err);
+		goto errsuper;
+	}
+
 	return err;
 errout:
+	brelse(dind);
+errsuper:
 	kvfree(n_group_desc);
 	brelse(iloc.bh);
-	brelse(dind);
 	brelse(gdb_bh);
 
 	ext4_debug("leaving with error %d\n", err);
-- 
2.17.1

Re: [PATCH] ext4: Fix memleak in add_new_gdb

[Jan Kara]

On Thu 27-08-20 14:28:43, Dinghao Liu wrote:
> When ext4_journal_get_write_access() fails, we should release
> n_group_desc, iloc.bh, dind and gdb_bh to prevent memleak.
> It's the same when ext4_handle_dirty_super() fails, but we
> don't need to release dind here because it has been released
> before.
> 
> Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>

Thanks for the patch! Some comments below:

> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index a50b51270ea9..efc0a022ca8e 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -843,8 +843,10 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
>  
>  	BUFFER_TRACE(dind, "get_write_access");
>  	err = ext4_journal_get_write_access(handle, dind);
> -	if (unlikely(err))
> +	if (unlikely(err)) {
>  		ext4_std_error(sb, err);
> +		goto errout;
> +	}

This hunk looks good.

> @@ -899,13 +901,17 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
>  
>  	le16_add_cpu(&es->s_reserved_gdt_blocks, -1);
>  	err = ext4_handle_dirty_super(handle, sb);
> -	if (err)
> +	if (err) {
>  		ext4_std_error(sb, err);
> +		goto errsuper;
> +	}
> +
>  	return err;
>  errout:
> +	brelse(dind);
> +errsuper:

But this is definitely wrong. Look, n_group_desc and gdb_bh are already
referenced from the superblock so you cannot free them, iloc.bh has been
released in ext4_mark_iloc_dirty().

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: Re: [PATCH] ext4: Fix memleak in add_new_gdb

[dinghao.liu]

> On Thu 27-08-20 14:28:43, Dinghao Liu wrote:
> > When ext4_journal_get_write_access() fails, we should release
> > n_group_desc, iloc.bh, dind and gdb_bh to prevent memleak.
> > It's the same when ext4_handle_dirty_super() fails, but we
> > don't need to release dind here because it has been released
> > before.
> > 
> > Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
> 
> Thanks for the patch! Some comments below:
> 
> > diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> > index a50b51270ea9..efc0a022ca8e 100644
> > --- a/fs/ext4/resize.c
> > +++ b/fs/ext4/resize.c
> > @@ -843,8 +843,10 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
> >  
> >  	BUFFER_TRACE(dind, "get_write_access");
> >  	err = ext4_journal_get_write_access(handle, dind);
> > -	if (unlikely(err))
> > +	if (unlikely(err)) {
> >  		ext4_std_error(sb, err);
> > +		goto errout;
> > +	}
> 
> This hunk looks good.
> 
> > @@ -899,13 +901,17 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
> >  
> >  	le16_add_cpu(&es->s_reserved_gdt_blocks, -1);
> >  	err = ext4_handle_dirty_super(handle, sb);
> > -	if (err)
> > +	if (err) {
> >  		ext4_std_error(sb, err);
> > +		goto errsuper;
> > +	}
> > +
> >  	return err;
> >  errout:
> > +	brelse(dind);
> > +errsuper:
> 
> But this is definitely wrong. Look, n_group_desc and gdb_bh are already
> referenced from the superblock so you cannot free them, iloc.bh has been
> released in ext4_mark_iloc_dirty().
> 

Thank you for your advice! It's clear to me and I will fix this soon.

Regards,
Dinghao