release/5.2.54/drm-amdgpu-Fix-NULL-dereference-in-dpm-sysfs-handler.patch

From d6fe87308ef477c2dfdd4aa00b1a988b5ebf138d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Gronowski?= <me@woland.xyz>
Date: Sun, 19 Jul 2020 17:54:53 +0200
Subject: [PATCH] drm/amdgpu: Fix NULL dereference in dpm sysfs handlers
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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: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
index 059f99534d77..557e8deadc9c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
@@ -681,8 +681,7 @@ static ssize_t amdgpu_set_pp_od_clk_voltage(struct device *dev,
 		tmp_str++;
 	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;
@@ -867,8 +866,7 @@ 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)
@@ -1274,8 +1272,7 @@ 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;
-- 
2.27.0