drm/amdgpu: Fix NULL dereference in dpm sysfs handlers

commit 38e0c89a19fd13f28d2b4721035160a3e66e270b upstream.

NULL dereference occurs when string that is not ended with space or
newline is written to some dpm sysfs interface (for example pp_dpm_sclk).
This happens because strsep replaces the tmp with NULL if the delimiter
is not present in string, which is then dereferenced by tmp[0].

Reproduction example:
sudo sh -c 'echo -n 1 > /sys/class/drm/card0/device/pp_dpm_sclk'

Signed-off-by: Paweł Gronowski <me@woland.xyz>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
index e63a253eb42550e548df03c6d819d27bfe191d03..7bea8ba89e88353c4e26f81c89c9c6490069558f 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
@@ -529,8 +529,7 @@ static ssize_t amdgpu_set_pp_od_clk_voltage(struct device *dev,
 
        while (isspace(*++tmp_str));
 
-       while (tmp_str[0]) {
-               sub_str = strsep(&tmp_str, delimiter);
+       while ((sub_str = strsep(&tmp_str, delimiter)) != NULL) {
                ret = kstrtol(sub_str, 0, &parameter[parameter_size]);
                if (ret)
                        return -EINVAL;
@@ -630,8 +629,7 @@ static ssize_t amdgpu_read_mask(const char *buf, size_t count, uint32_t *mask)
        memcpy(buf_cpy, buf, bytes);
        buf_cpy[bytes] = '\0';
        tmp = buf_cpy;
-       while (tmp[0]) {
-               sub_str = strsep(&tmp, delimiter);
+       while ((sub_str = strsep(&tmp, delimiter)) != NULL) {
                if (strlen(sub_str)) {
                        ret = kstrtol(sub_str, 0, &level);
                        if (ret)
@@ -882,8 +880,7 @@ static ssize_t amdgpu_set_pp_power_profile_mode(struct device *dev,
                        i++;
                memcpy(buf_cpy, buf, count-i);
                tmp_str = buf_cpy;
-               while (tmp_str[0]) {
-                       sub_str = strsep(&tmp_str, delimiter);
+               while ((sub_str = strsep(&tmp_str, delimiter)) != NULL) {
                        ret = kstrtol(sub_str, 0, &parameter[parameter_size]);
                        if (ret) {
                                count = -EINVAL;