Re: [PATCH] ext4: get rid of ppath in get_ext_path()

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Jun 26, 2026 at 01:17:21PM +0800, Wang Jun wrote:
> [ Upstream commit 6b854d552711aa33f59eda334e6d94a00d8825bb ]
> 
> The use of path and ppath is now very confusing, so to make the code more
> readable, pass path between functions uniformly, and get rid of ppath.
> 
> After getting rid of ppath in get_ext_path(), its caller may pass an error
> pointer to ext4_free_ext_path(), so it needs to teach ext4_free_ext_path()
> and ext4_ext_drop_refs() to skip the error pointer. No functional changes.
> 
> Without this fix, ext4_ext_insert_extent() returning ERR_PTR(-ENOSPC) in
> ext4_ext_map_blocks() triggers a kernel Oops, observed via SyzKing
> fuzzing on v6.6.142:
> 
>   BUG: unable to handle page fault for address: ffffffffffffffec
>   R15: ffffffffffffffe4  (= ERR_PTR(-ENOSPC))
>   RIP: ext4_ext_drop_refs+0x...->ext4_free_ext_path+0x...->
>        ext4_ext_map_blocks+0x509/0x53a0
> 
> Signed-off-by: Baokun Li <libaokun1@huawei.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> Signed-off-by: Wang Jun <1742789905@qq.com>
> ---
>  fs/ext4/extents.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index a94798e23..8e23563bb 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4510,7 +4510,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>  	allocated = map->m_len;
>  	ext4_ext_show_leaf(inode, path);
>  out:
> -	ext4_free_ext_path(path);
> +	if (!IS_ERR(path))
> +		ext4_free_ext_path(path);
>  
>  	trace_ext4_ext_map_blocks_exit(inode, flags, map,
>  				       err ? err : allocated);
> -- 
> 2.43.0
> 
> 

What stable kernel(s) is this for?