This is a note to let you know that I've just added the patch titled
drm/radeon: fix possible division-by-zero errors
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-radeon-fix-possible-division-by-zero-errors.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7b737e2a192e5411fcf868db4dc700d9e0c467c2
Author: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
Date: Fri May 19 08:33:27 2023 -0700
drm/radeon: fix possible division-by-zero errors
[ Upstream commit 1becc57cd1a905e2aa0e1eca60d2a37744525c4a ]
Function rv740_get_decoded_reference_divider() may return 0 due to
unpredictable reference divider value calculated in
radeon_atom_get_clock_dividers(). This will lead to
division-by-zero error once that value is used as a divider
in calculating 'clk_s'.
While unlikely, this issue should nonetheless be prevented so add a
sanity check for such cases by testing 'decoded_ref' value against 0.
Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.
v2: minor coding style fixes (Alex)
In practice this should actually happen as the vbios should be
properly populated.
Fixes: 66229b200598 ("drm/radeon/kms: add dpm support for rv7xx (v4)")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/radeon/cypress_dpm.c b/drivers/gpu/drm/radeon/cypress_dpm.c
index 32ed60f1048bd..b31d65a6752f1 100644
--- a/drivers/gpu/drm/radeon/cypress_dpm.c
+++ b/drivers/gpu/drm/radeon/cypress_dpm.c
@@ -559,8 +559,12 @@ static int cypress_populate_mclk_value(struct radeon_device *rdev,
ASIC_INTERNAL_MEMORY_SS, vco_freq)) {
u32 reference_clock = rdev->clock.mpll.reference_freq;
u32 decoded_ref = rv740_get_decoded_reference_divider(dividers.ref_div);
- u32 clk_s = reference_clock * 5 / (decoded_ref * ss.rate);
- u32 clk_v = ss.percentage *
+ u32 clk_s, clk_v;
+
+ if (!decoded_ref)
+ return -EINVAL;
+ clk_s = reference_clock * 5 / (decoded_ref * ss.rate);
+ clk_v = ss.percentage *
(0x4000 * dividers.whole_fb_div + 0x800 * dividers.frac_fb_div) / (clk_s * 625);
mpll_ss1 &= ~CLKV_MASK;
diff --git a/drivers/gpu/drm/radeon/ni_dpm.c b/drivers/gpu/drm/radeon/ni_dpm.c
index 288ec3039bc2c..cad7a73a551f7 100644
--- a/drivers/gpu/drm/radeon/ni_dpm.c
+++ b/drivers/gpu/drm/radeon/ni_dpm.c
@@ -2241,8 +2241,12 @@ static int ni_populate_mclk_value(struct radeon_device *rdev,
ASIC_INTERNAL_MEMORY_SS, vco_freq)) {
u32 reference_clock = rdev->clock.mpll.reference_freq;
u32 decoded_ref = rv740_get_decoded_reference_divider(dividers.ref_div);
- u32 clk_s = reference_clock * 5 / (decoded_ref * ss.rate);
- u32 clk_v = ss.percentage *
+ u32 clk_s, clk_v;
+
+ if (!decoded_ref)
+ return -EINVAL;
+ clk_s = reference_clock * 5 / (decoded_ref * ss.rate);
+ clk_v = ss.percentage *
(0x4000 * dividers.whole_fb_div + 0x800 * dividers.frac_fb_div) / (clk_s * 625);
mpll_ss1 &= ~CLKV_MASK;
diff --git a/drivers/gpu/drm/radeon/rv740_dpm.c b/drivers/gpu/drm/radeon/rv740_dpm.c
index 327d65a76e1f4..79b2de65e905e 100644
--- a/drivers/gpu/drm/radeon/rv740_dpm.c
+++ b/drivers/gpu/drm/radeon/rv740_dpm.c
@@ -250,8 +250,12 @@ int rv740_populate_mclk_value(struct radeon_device *rdev,
ASIC_INTERNAL_MEMORY_SS, vco_freq)) {
u32 reference_clock = rdev->clock.mpll.reference_freq;
u32 decoded_ref = rv740_get_decoded_reference_divider(dividers.ref_div);
- u32 clk_s = reference_clock * 5 / (decoded_ref * ss.rate);
- u32 clk_v = 0x40000 * ss.percentage *
+ u32 clk_s, clk_v;
+
+ if (!decoded_ref)
+ return -EINVAL;
+ clk_s = reference_clock * 5 / (decoded_ref * ss.rate);
+ clk_v = 0x40000 * ss.percentage *
(dividers.whole_fb_div + (dividers.frac_fb_div / 8)) / (clk_s * 10000);
mpll_ss1 &= ~CLKV_MASK;
