[PATCH] fs: ext4fs: Free memory while handling errors

[Quentin Schulz]

Hi Francois,

On 12/9/25 9:59 AM, Francois Berder wrote:
> If zalloc fails, one needs to free memory previously
> allocated in the function. This commit makes sure that
> we do not leak any memory.
> 
> Signed-off-by: Francois Berder <fberder at outlook.fr>
> ---
>   fs/ext4/ext4_common.c  | 8 +++++++-
>   fs/ext4/ext4_journal.c | 4 +++-
>   fs/ext4/ext4_write.c   | 2 ++
>   3 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
> index 8e6531fa3f0..f48a8ca48d3 100644
> --- a/fs/ext4/ext4_common.c
> +++ b/fs/ext4/ext4_common.c
> @@ -727,8 +727,14 @@ static int parse_path(char **arr, char *dirname)
>   	/* add each path entry after root */
>   	while (token != NULL) {
>   		arr[i] = zalloc(strlen(token) + 1);
> -		if (!arr[i])
> +		if (!arr[i]) {
> +			int j;
> +
> +			for (j = 0; j < i; j++)
> +				free(arr[j]);
> +

Simply reuse i?

for (--i; i >= 0; i--)
     free(arr[i]);

? (i being an int makes i >= 0 safe in the loop condition (as in "won't 
happen") wrt underflow)

>   			return -ENOMEM;
> +		}
>   		memcpy(arr[i++], token, strlen(token));
>   		token = strtok(NULL, "/");
>   	}
> diff --git a/fs/ext4/ext4_journal.c b/fs/ext4/ext4_journal.c
> index 868a2c1804a..3a2e9f30c12 100644
> --- a/fs/ext4/ext4_journal.c
> +++ b/fs/ext4/ext4_journal.c
> @@ -256,8 +256,10 @@ void ext4fs_push_revoke_blk(char *buffer)
>   	}
>   
>   	node->content = zalloc(fs->blksz);
> -	if (node->content == NULL)
> +	if (!node->content) {
> +		free(node);
>   		return;
> +	}
>   	memcpy(node->content, buffer, fs->blksz);
>   
>   	if (first_node == true) {
> diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c
> index 5b290f0d80d..20d4e47fd38 100644
> --- a/fs/ext4/ext4_write.c
> +++ b/fs/ext4/ext4_write.c
> @@ -204,6 +204,7 @@ static void delete_double_indirect_block(struct ext2_inode *inode)
>   	if (inode->b.blocks.double_indir_block != 0) {
>   		di_buffer = zalloc(fs->blksz);
>   		if (!di_buffer) {
> +			free(journal_buffer);
>   			printf("No memory\n");

What about just doing

goto fail;

here? As it'll free both dib_start_addr and journal_buffer (and that it 
seems free(x) shall check for x == NULL before doing anything).

>   			return;
>   		}
> @@ -303,6 +304,7 @@ static void delete_triple_indirect_block(struct ext2_inode *inode)
>   	if (inode->b.blocks.triple_indir_block != 0) {
>   		tigp_buffer = zalloc(fs->blksz);
>   		if (!tigp_buffer) {
> +			free(journal_buffer);
>   			printf("No memory\n");

Ditto.

Cheers,
Quentin