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_strtol() 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 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 | 98 ++++++++++++------------------------ 1 file changed, 33 insertions(+), 65 deletions(-)

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c index 9ccedb3264fb..046fa682d57d 100644 --- a/drivers/w1/slaves/w1_therm.c +++ b/drivers/w1/slaves/w1_therm.c @@ -1836,59 +1836,32 @@ 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 temp; + int ret; s8 tl, th; /* 1 byte per value + temp ring order */ - char *p_args, *orig; + const char *p = buf; + char *endp;

- 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; + temp = simple_strtol(p, &endp, 10); + if (p == endp || *endp != ' ') { + dev_info(device, "%s: error parsing args %d\n", + __func__, -EINVAL); + goto err; } - 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); - if (ret) { - dev_info(device, - "%s: error parsing args %d\n", __func__, ret); - goto free_m; - } - + /* Cast to short to eliminate out of range values */ 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); - if (ret) { - dev_info(device, - "%s: error parsing args %d\n", __func__, ret); - goto free_m; + p = endp + 1; + temp = simple_strtol(p, &endp, 10); + if (p == endp) { + dev_info(device, "%s: error parsing args %d\n", + __func__, -EINVAL); + goto err; } - - /* Prepare to cast to short by eliminating out of range values */ + /* Cast to short to eliminate out of range values */ th = int_to_short(temp);

- /* Reorder if required th and tl */ + /* Reorder if required */ if (tl > th) swap(tl, th);

@@ -1897,35 +1870,30 @@ static ssize_t alarms_store(struct device *device, * (th : byte 2 - tl: byte 3) */ ret = read_scratchpad(sl, &info); - if (!ret) { - new_config_register[0] = th; /* Byte 2 */ - new_config_register[1] = tl; /* Byte 3 */ - new_config_register[2] = info.rom[4];/* Byte 4 */ - } else { - dev_info(device, - "%s: error reading from the slave device %d\n", - __func__, ret); - goto free_m; + if (ret) { + dev_info(device, "%s: error reading from the slave device %d\n", + __func__, ret); + goto err; } + new_config_register[0] = th; /* Byte 2 */ + new_config_register[1] = tl; /* Byte 3 */ + new_config_register[2] = info.rom[4]; /* Byte 4 */

/* Write data in the device RAM */ if (!SLAVE_SPECIFIC_FUNC(sl)) { - dev_info(device, - "%s: Device not supported by the driver %d\n", - __func__, -ENODEV); - goto free_m; + dev_info(device, "%s: Device not supported by the driver %d\n", + __func__, -ENODEV); + goto err; }

ret = SLAVE_SPECIFIC_FUNC(sl)->write_data(sl, new_config_register); - if (ret) - dev_info(device, - "%s: error writing to the slave device %d\n", + if (ret) { + dev_info(device, "%s: error writing to the slave device %d\n", __func__, ret); + goto err; + }

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