Re: [PATCH][next][V3] btrfs: fix memory leak of path on error return path

[Nikolay Borisov]

On 5.07.19 Ð. 10:26 Ñ., Colin King wrote:
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> 
> Currently if the allocation of roots or tmp_ulist fails the error handling
> does not free up the allocation of path causing a memory leak. Fix this and
> other similar leaks by moving the call of btrfs_free_path from label out
> to label out_free_ulist.
> 
> Kudos to David Sterba for spotting the issue in my original fix and suggesting
> the correct way to fix the leak and Anand Jain for spotting a double free
> issue.
> 
> Addresses-Coverity: ("Resource leak")
> Fixes: 5911c8fe05c5 ("btrfs: fiemap: preallocate ulists for btrfs_check_shared")
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>

Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>

> ---
> V2: move the btrfs_free_path to the out_free_ulist label as suggested by
>      David Sterba as the correct fix.
> V3: fix double free as identified Anand Jain
> ---
> 
>  fs/btrfs/extent_io.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 1eb671c16ff1..9de119194f8e 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -4613,7 +4613,6 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>  	ret = btrfs_lookup_file_extent(NULL, root, path,
>  			btrfs_ino(BTRFS_I(inode)), -1, 0);
>  	if (ret < 0) {
> -		btrfs_free_path(path);
>  		goto out_free_ulist;
>  	} else {
>  		WARN_ON(!ret);
> @@ -4766,11 +4765,11 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>  		ret = emit_last_fiemap_cache(fieinfo, &cache);
>  	free_extent_map(em);
>  out:
> -	btrfs_free_path(path);
>  	unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len - 1,
>  			     &cached_state);
>  
>  out_free_ulist:
> +	btrfs_free_path(path);
>  	ulist_free(roots);
>  	ulist_free(tmp_ulist);
>  	return ret;
>