linux-kernel - [PATCH] drm/nouveau: fix potential abnormal lock/unlock

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Date:   Fri,  2 Apr 2021 01:55:47 -0700
From:   Bernard Zhao <bernard@...o.com>
To:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Lyude Paul <lyude@...hat.com>,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     Bernard Zhao <bernard@...o.com>
Subject: [PATCH] drm/nouveau: fix potential abnormal lock/unlock

Fix coccicheck warning:
drivers/gpu/drm/nouveau/nvkm/engine/fifo/base.c:115:3-9: preceding lock on line 109
drivers/gpu/drm/nouveau/nvkm/engine/fifo/base.c:98:2-8: preceding lock on line 95

As we see, function nvkm_fifo_chan_inst & nvkm_fifo_chan_chid both
use spin_lock_irqsave, but no spin_unlock_irqrestore in if/return
branch, seems like a potential bug?

Signed-off-by: Bernard Zhao <bernard@...o.com>
---
 drivers/gpu/drm/nouveau/nvkm/engine/fifo/base.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/base.c b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/base.c
index 2ed4ff05d207..e3f624d97644 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/base.c
@@ -95,6 +95,7 @@ nvkm_fifo_chan_inst(struct nvkm_fifo *fifo, u64 inst, unsigned long *rflags)
 	spin_lock_irqsave(&fifo->lock, flags);
 	if ((chan = nvkm_fifo_chan_inst_locked(fifo, inst))) {
 		*rflags = flags;
+		spin_unlock_irqrestore(&fifo->lock, flags);
 		return chan;
 	}
 	spin_unlock_irqrestore(&fifo->lock, flags);
@@ -112,6 +113,7 @@ nvkm_fifo_chan_chid(struct nvkm_fifo *fifo, int chid, unsigned long *rflags)
 			list_del(&chan->head);
 			list_add(&chan->head, &fifo->chan);
 			*rflags = flags;
+			spin_unlock_irqrestore(&fifo->lock, flags);
 			return chan;
 		}
 	}
-- 
2.31.0