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Thu, 10 Apr 2025 23:59:18 -0700 (PDT) Message-ID: <0a1ea318-20e3-44b8-9d5e-f603c5341087@gmail.com> Date: Fri, 11 Apr 2025 12:29:14 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hwmon: asus_atk0110: NULL buf.pointer after free To: Guenter Roeck Cc: Luca Tettamanti , Jean Delvare , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250410183450.15514-1-purvayeshi550@gmail.com> Content-Language: en-US From: Purva Yeshi In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/04/25 01:34, Guenter Roeck wrote: > On Fri, Apr 11, 2025 at 12:04:50AM +0530, Purva Yeshi wrote: >> Fix Smatch-detected issue: >> drivers/hwmon/asus_atk0110.c:987 atk_enumerate_old_hwmon() error: >> double free of 'buf.pointer' (line 966) >> drivers/hwmon/asus_atk0110.c:1008 atk_enumerate_old_hwmon() error: >> double free of 'buf.pointer' (line 987) >> >> Smatch warns about double free of 'buf.pointer'. >> This happens because the same buffer struct is reused multiple times >> without resetting the pointer after free. Set buf.pointer = NULL >> after each ACPI_FREE to prevent possible use-after-free bugs. >> >> Signed-off-by: Purva Yeshi >> --- >> drivers/hwmon/asus_atk0110.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/hwmon/asus_atk0110.c b/drivers/hwmon/asus_atk0110.c >> index c80350e499e9..83ee7f25bb8e 100644 >> --- a/drivers/hwmon/asus_atk0110.c >> +++ b/drivers/hwmon/asus_atk0110.c >> @@ -964,6 +964,7 @@ static int atk_enumerate_old_hwmon(struct atk_data *data) >> count++; >> } >> ACPI_FREE(buf.pointer); >> + buf.pointer = NULL; >> >> /* Temperatures */ >> buf.length = ACPI_ALLOCATE_BUFFER; >> @@ -985,6 +986,7 @@ static int atk_enumerate_old_hwmon(struct atk_data *data) >> count++; >> } >> ACPI_FREE(buf.pointer); >> + buf.pointer = NULL; >> >> /* Fans */ >> buf.length = ACPI_ALLOCATE_BUFFER; > > buf.length is set to ACPI_ALLOCATE_BUFFER to trigger buffer > allocation in acpi_evaluate_object_typed(). The old content of > buf.pointer is irrelevant (and not initialized to start with > in the first call). The problem you describe does not exist. > > Guenter Thank you for the clarification, Guenter. I appreciate your review. > >> @@ -1006,6 +1008,7 @@ static int atk_enumerate_old_hwmon(struct atk_data *data) >> count++; >> } >> ACPI_FREE(buf.pointer); >> + buf.pointer = NULL; >> >> return count; >> } >> -- >> 2.34.1 >> >> Best regards, Purva