RE: [PATCH] dpll: Add a check before kfree() to match the existing check before kmemdup()

[Kubalewski, Arkadiusz]

Hi Jiasheng, many thanks for the patch!

>From: Jiasheng Jiang <jiashengjiangcool@xxxxxxxxx>
>Sent: Sunday, February 23, 2025 9:17 PM
>
>When src->freq_supported is not NULL but src->freq_supported_num is 0,
>dst->freq_supported is equal to src->freq_supported.
>In this case, if the subsequent kstrdup() fails, src->freq_supported may

The src->freq_supported is not being freed in this function,
you ment dst->freq_supported?
But also it is not true.
dst->freq_supported is being freed already, this patch adds only additional
condition over it..
>From kfree doc: "If @object is NULL, no operation is performed.".

>be freed without being set to NULL, potentially leading to a
>use-after-free or double-free error.
>

kfree does not set to NULL from what I know. How would it lead to
use-after-free/double-free?
Why the one would use the memory after the function returns -ENOMEM?

I don't think this patch is needed or resolves anything.

Thank you!
Arkadiusz

>Fixes: 830ead5fb0c5 ("dpll: fix pin dump crash for rebound module")
>Cc: <stable@xxxxxxxxxxxxxxx> # v6.8+
>Signed-off-by: Jiasheng Jiang <jiashengjiangcool@xxxxxxxxx>
>---
> drivers/dpll/dpll_core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
>index 32019dc33cca..7d147adf8455 100644
>--- a/drivers/dpll/dpll_core.c
>+++ b/drivers/dpll/dpll_core.c
>@@ -475,7 +475,8 @@ static int dpll_pin_prop_dup(const struct
>dpll_pin_properties *src,
> err_panel_label:
> 	kfree(dst->board_label);
> err_board_label:
>-	kfree(dst->freq_supported);
>+	if (src->freq_supported_num)
>+		kfree(dst->freq_supported);
> 	return -ENOMEM;
> }
>
>--
>2.25.1