Subject: Re: [PATCH v5 01/16] reftable: fix OOB stack write in print functions

From: Junio C Hamano <[email-masked]>
Date: Wed, 22 Dec 2021 14:51:25 -0800

"Han-Wen Nienhuys via GitGitGadget" <[email-masked]> writes:

> From: Han-Wen Nienhuys <[email-masked]>
>
> Signed-off-by: Han-Wen Nienhuys <[email-masked]>
> ---
>  reftable/record.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/reftable/record.c b/reftable/record.c
> index 6a5dac32dc6..8536bd03aa9 100644
> --- a/reftable/record.c
> +++ b/reftable/record.c
> @@ -254,7 +254,7 @@ static void hex_format(char *dest, uint8_t *src, int hash_size)
>  void reftable_ref_record_print(struct reftable_ref_record *ref,
>  			       uint32_t hash_id)
>  {
> -	char hex[2 * GIT_SHA256_RAWSZ + 1] = { 0 }; /* BUG */
> +	char hex[GIT_MAX_HEXSZ + 1] = { 0 }; /* BUG */
>  	printf("ref{%s(%" PRIu64 ") ", ref->refname, ref->update_index);
>  	switch (ref->value_type) {
>  	case REFTABLE_REF_SYMREF:
> @@ -586,7 +586,7 @@ static struct reftable_record_vtable reftable_obj_record_vtable = {
>  void reftable_log_record_print(struct reftable_log_record *log,
>  			       uint32_t hash_id)
>  {
> -	char hex[GIT_SHA256_RAWSZ + 1] = { 0 };
> +	char hex[GIT_MAX_HEXSZ + 1] = { 0 };
>  
>  	switch (log->value_type) {
>  	case REFTABLE_LOG_DELETION:

Wow.  The first one is future-proofing in case we learn to use even
larger hash, but the latter is an outright bug that makes reviewers
feel embarrassed, isn't it?

Thanks for noticing and fixing it.