linux-kernel - [PATCH AUTOSEL 5.4 062/108] drm/amd/display: System crashes when add_ptb_to

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Date:   Sat, 11 Apr 2020 19:08:57 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Peikang Zhang <peikang.zhang@....com>, Aric Cyr <Aric.Cyr@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Harry Wentland <harry.wentland@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.4 062/108] drm/amd/display: System crashes when add_ptb_to_table() gets called

From: Peikang Zhang <peikang.zhang@....com>

[ Upstream commit 0062972b9d9f888d0273c6496769d02e8f509135 ]

[Why]
Unused VMIDs were not evicted correctly

[How]
1. evict_vmids() logic was fixed;
2. Added boundary check for add_ptb_to_table() and
   clear_entry_from_vmid_table() to avoid crash caused by array out of
   boundary;
3. For mod_vmid_get_for_ptb(), vimd is changed from unsigned to signed
   due to vimd is signed.

Signed-off-by: Peikang Zhang <peikang.zhang@....com>
Reviewed-by: Aric Cyr <Aric.Cyr@....com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@....com>
Acked-by: Harry Wentland <harry.wentland@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/modules/vmid/vmid.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/modules/vmid/vmid.c b/drivers/gpu/drm/amd/display/modules/vmid/vmid.c
index f0a153704f6e0..00f132f8ad55d 100644
--- a/drivers/gpu/drm/amd/display/modules/vmid/vmid.c
+++ b/drivers/gpu/drm/amd/display/modules/vmid/vmid.c
@@ -40,14 +40,18 @@ struct core_vmid {
 
 static void add_ptb_to_table(struct core_vmid *core_vmid, unsigned int vmid, uint64_t ptb)
 {
-	core_vmid->ptb_assigned_to_vmid[vmid] = ptb;
-	core_vmid->num_vmids_available--;
+	if (vmid < MAX_VMID) {
+		core_vmid->ptb_assigned_to_vmid[vmid] = ptb;
+		core_vmid->num_vmids_available--;
+	}
 }
 
 static void clear_entry_from_vmid_table(struct core_vmid *core_vmid, unsigned int vmid)
 {
-	core_vmid->ptb_assigned_to_vmid[vmid] = 0;
-	core_vmid->num_vmids_available++;
+	if (vmid < MAX_VMID) {
+		core_vmid->ptb_assigned_to_vmid[vmid] = 0;
+		core_vmid->num_vmids_available++;
+	}
 }
 
 static void evict_vmids(struct core_vmid *core_vmid)
@@ -57,7 +61,7 @@ static void evict_vmids(struct core_vmid *core_vmid)
 
 	// At this point any positions with value 0 are unused vmids, evict them
 	for (i = 1; i < core_vmid->num_vmid; i++) {
-		if (ord & (1u << i))
+		if (!(ord & (1u << i)))
 			clear_entry_from_vmid_table(core_vmid, i);
 	}
 }
@@ -91,7 +95,7 @@ static int get_next_available_vmid(struct core_vmid *core_vmid)
 uint8_t mod_vmid_get_for_ptb(struct mod_vmid *mod_vmid, uint64_t ptb)
 {
 	struct core_vmid *core_vmid = MOD_VMID_TO_CORE(mod_vmid);
-	unsigned int vmid = 0;
+	int vmid = 0;
 
 	// Physical address gets vmid 0
 	if (ptb == 0)
-- 
2.20.1