From 4481913607e58196c48a4fef5e6f45350684ec3c Mon Sep 17 00:00:00 2001
From: Yunxiang Li <Yunxiang.Li@amd.com>
Date: Thu, 22 Jun 2023 10:18:03 -0400
Subject: [PATCH] drm/ttm: fix bulk_move corruption when adding a entry
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Git-commit: 4481913607e58196c48a4fef5e6f45350684ec3c
Patch-mainline: v6.5-rc2
References: git-fixes

When the resource is the first in the bulk_move range, adding it again
(thus moving it to the tail) will corrupt the list since the first
pointer is not moved. This eventually lead to null pointer deref in
ttm_lru_bulk_move_del()

Fixes: fee2ede15542 ("drm/ttm: rework bulk move handling v5")
Signed-off-by: Yunxiang Li <Yunxiang.Li@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20230622141902.28718-3-Yunxiang.Li@amd.com
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/ttm/ttm_resource.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 7333f7a87a2f..e51dbc7a2d53 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -86,6 +86,8 @@ static void ttm_lru_bulk_move_pos_tail(struct ttm_lru_bulk_move_pos *pos,
 				       struct ttm_resource *res)
 {
 	if (pos->last != res) {
+		if (pos->first == res)
+			pos->first = list_next_entry(res, lru);
 		list_move(&res->lru, &pos->last->lru);
 		pos->last = res;
 	}
@@ -111,7 +113,8 @@ static void ttm_lru_bulk_move_del(struct ttm_lru_bulk_move *bulk,
 {
 	struct ttm_lru_bulk_move_pos *pos = ttm_lru_bulk_move_pos(bulk, res);
 
-	if (unlikely(pos->first == res && pos->last == res)) {
+	if (unlikely(WARN_ON(!pos->first || !pos->last) ||
+		     pos->first == res && pos->last == res)) {
 		pos->first = NULL;
 		pos->last = NULL;
 	} else if (pos->first == res) {
-- 
2.35.3