linux-kernel - Re: [PATCH] tools/hv: Memory Leak on realloc

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Message-ID: <CAE2+fR9kaSGz8pfi-vbmeXGXM84ANyBTD2C1VJg6aFSVyVffrA@mail.gmail.com>
Date: Sat, 5 Apr 2025 11:39:02 +0530
From: malaya kumar rout <malayarout91@...il.com>
To: malayarout91@...il.com
Cc: linux-kernel@...r.kernel.org, "K. Y. Srinivasan" <kys@...rosoft.com>, 
	Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, 
	Dexuan Cui <decui@...rosoft.com>, linux-hyperv@...r.kernel.org
Subject: Re: [PATCH] tools/hv: Memory Leak on realloc

On Sat, Mar 22, 2025 at 10:17 PM Malaya Kumar Rout
<malayarout91@...il.com> wrote:
>
> Static analysis for hv_kvp_daemon.c with cppcheck : error:
>
> hv_kvp_daemon.c:359:3: error: Common realloc mistake:
> 'record' nulled but not freed upon failure [memleakOnRealloc]
> record = realloc(record, sizeof(struct kvp_record) *
>
> If realloc() fails, record is now NULL.
> If we directly assign this NULL to record, the reference to the previously allocated memory is lost.
> This causes a memory leak because the old allocated memory remains but is no longer accessible.
>
> A temporary pointer was utilized when invoking realloc() to prevent
> the loss of the original allocation in the event of a failure
>
> CC: linux-kernel@...r.kernel.org
>     linux-hyperv@...r.kernel.org
> Signed-off-by: Malaya Kumar Rout <malayarout91@...il.com>
> ---
>  tools/hv/hv_kvp_daemon.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
> index 04ba035d67e9..6807832209f0 100644
> --- a/tools/hv/hv_kvp_daemon.c
> +++ b/tools/hv/hv_kvp_daemon.c
> @@ -356,11 +356,14 @@ static int kvp_key_add_or_modify(int pool, const __u8 *key, int key_size,
>          */
>         if (num_records == (ENTRIES_PER_BLOCK * num_blocks)) {
>                 /* Need to allocate a larger array for reg entries. */
> -               record = realloc(record, sizeof(struct kvp_record) *
> -                        ENTRIES_PER_BLOCK * (num_blocks + 1));
> -
> -               if (record == NULL)
> +               struct kvp_record *temp = realloc(record, sizeof(struct kvp_record) *
> +                               ENTRIES_PER_BLOCK * (num_blocks + 1));
> +               if (!temp) {
> +                       free(record);
> +                       record = NULL;
>                         return 1;
> +               }
> +               record = temp;
>                 kvp_file_info[pool].num_blocks++;
>
>         }
> --
> 2.43.0
>

This is a courteous reminder regarding the current patch.
Any feedback or insights you may have would be greatly appreciated.

Thanks & Regards,
Malaya Kumar Rout