linux-hardening - Re: [PATCH] scsi: target: Replace strlcpy with strscpy

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Date:   Wed, 30 Aug 2023 16:11:34 -0400
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-hardening@...r.kernel.org, linux-scsi@...r.kernel.org,
        target-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: target: Replace strlcpy with strscpy

Please ignore this patch. There are more strlcpy()->strscpy()
replacement in the same file that did not get included here. Will send
out a v2 with all the changes to make it easier for reviewers.

On Wed, Aug 30, 2023 at 4:07 PM Azeem Shaikh <azeemshaikh38@...il.com> wrote:
>
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
>
> Direct replacement is safe here since return value of -errno
> is used to check for truncation instead of sizeof(dest).
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
>
> Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
> ---
>  drivers/target/target_core_configfs.c |    9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> index 936e5ff1b209..b3d2c14e2ea9 100644
> --- a/drivers/target/target_core_configfs.c
> +++ b/drivers/target/target_core_configfs.c
> @@ -1392,16 +1392,15 @@ static ssize_t target_wwn_vendor_id_store(struct config_item *item,
>         /* +2 to allow for a trailing (stripped) '\n' and null-terminator */
>         unsigned char buf[INQUIRY_VENDOR_LEN + 2];
>         char *stripped = NULL;
> -       size_t len;
> +       ssize_t len;
>         ssize_t ret;
>
> -       len = strlcpy(buf, page, sizeof(buf));
> -       if (len < sizeof(buf)) {
> +       len = strscpy(buf, page, sizeof(buf));
> +       if (len > 0) {
>                 /* Strip any newline added from userspace. */
>                 stripped = strstrip(buf);
> -               len = strlen(stripped);
>         }
> -       if (len > INQUIRY_VENDOR_LEN) {
> +       if (len < 0 || strlen(stripped) > INQUIRY_VENDOR_LEN) {
>                 pr_err("Emulated T10 Vendor Identification exceeds"
>                         " INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
>                         "\n");
> --
> 2.42.0.283.g2d96d420d3-goog
>
>