The sysfs buffer passed to alarms_store() is allocated with 'size + 1' bytes and a NUL terminator is appended. However, the 'size' argument does not account for this extra byte. The original code then allocated 'size' bytes and used strcpy() to copy 'buf', which always writes one byte past the allocated buffer since strcpy() copies until the NUL terminator at index 'size'.

Fix this by parsing the 'buf' parameter directly using simple_strtoll() without allocating any intermediate memory or string copying. This removes the overflow while simplifying the code.

Cc: stable@vger.kernel.org Fixes: e2c94d6f5720 ("w1_therm: adding alarm sysfs entry") Signed-off-by: Thorsten Blum thorsten.blum@linux.dev --- Compile-tested only.

Changes in v5: - Replace gotos with return size (Krzysztof) - Link to v4: https://lore.kernel.org/lkml/20251111204422.41993-2-thorsten.blum@linux.dev/

Changes in v4: - Use simple_strtoll because kstrtoint also parses long long internally - Return -ERANGE in addition to -EINVAL to match kstrtoint's behavior - Remove any changes unrelated to fixing the buffer overflow (Krzysztof) while maintaining the same behavior and return values as before - Link to v3: https://lore.kernel.org/lkml/20251030155614.447905-1-thorsten.blum@linux.dev...

Changes in v3: - Add integer range check for 'temp' to match kstrtoint() behavior - Explicitly cast 'temp' to int when calling int_to_short() - Link to v2: https://lore.kernel.org/lkml/20251029130045.70127-2-thorsten.blum@linux.dev/

Changes in v2: - Fix buffer overflow instead of truncating the copy using strscpy() - Parse buffer directly using simple_strtol() as suggested by David - Update patch subject and description - Link to v1: https://lore.kernel.org/lkml/20251017170047.114224-2-thorsten.blum@linux.dev... --- drivers/w1/slaves/w1_therm.c | 63 ++++++++++++------------------------ 1 file changed, 20 insertions(+), 43 deletions(-)

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c index 9ccedb3264fb..5c4e40883400 100644 --- a/drivers/w1/slaves/w1_therm.c +++ b/drivers/w1/slaves/w1_therm.c @@ -1836,55 +1836,36 @@ static ssize_t alarms_store(struct device *device, struct w1_slave *sl = dev_to_w1_slave(device); struct therm_info info; u8 new_config_register[3]; /* array of data to be written */ - int temp, ret; - char *token = NULL; + long long temp; + int ret = 0; s8 tl, th; /* 1 byte per value + temp ring order */ - char *p_args, *orig; - - p_args = orig = kmalloc(size, GFP_KERNEL); - /* Safe string copys as buf is const */ - if (!p_args) { - dev_warn(device, - "%s: error unable to allocate memory %d\n", - __func__, -ENOMEM); - return size; - } - strcpy(p_args, buf); - - /* Split string using space char */ - token = strsep(&p_args, " "); - - if (!token) { - dev_info(device, - "%s: error parsing args %d\n", __func__, -EINVAL); - goto free_m; - } - - /* Convert 1st entry to int */ - ret = kstrtoint (token, 10, &temp); + const char *p = buf; + char *endp; + + temp = simple_strtoll(p, &endp, 10); + if (p == endp || *endp != ' ') + ret = -EINVAL; + else if (temp < INT_MIN || temp > INT_MAX) + ret = -ERANGE; if (ret) { dev_info(device, "%s: error parsing args %d\n", __func__, ret); - goto free_m; + return size; }

tl = int_to_short(temp);

- /* Split string using space char */ - token = strsep(&p_args, " "); - if (!token) { - dev_info(device, - "%s: error parsing args %d\n", __func__, -EINVAL); - goto free_m; - } - /* Convert 2nd entry to int */ - ret = kstrtoint (token, 10, &temp); + p = endp + 1; + temp = simple_strtoll(p, &endp, 10); + if (p == endp) + ret = -EINVAL; + else if (temp < INT_MIN || temp > INT_MAX) + ret = -ERANGE; if (ret) { dev_info(device, "%s: error parsing args %d\n", __func__, ret); - goto free_m; + return size; } - /* Prepare to cast to short by eliminating out of range values */ th = int_to_short(temp);

@@ -1905,7 +1886,7 @@ static ssize_t alarms_store(struct device *device, dev_info(device, "%s: error reading from the slave device %d\n", __func__, ret); - goto free_m; + return size; }

/* Write data in the device RAM */ @@ -1913,7 +1894,7 @@ static ssize_t alarms_store(struct device *device, dev_info(device, "%s: Device not supported by the driver %d\n", __func__, -ENODEV); - goto free_m; + return size; }

ret = SLAVE_SPECIFIC_FUNC(sl)->write_data(sl, new_config_register); @@ -1922,10 +1903,6 @@ static ssize_t alarms_store(struct device *device, "%s: error writing to the slave device %d\n", __func__, ret);

-free_m: - /* free allocated memory */ - kfree(orig); - return size; }