linux-kernel - [PATCH] mmc: core: Add error check to avoid kernel panic caused by NULL pointer

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Date:   Wed,  3 Jun 2020 01:29:57 +0800
From:   Corey Gao <gaoce123@...il.com>
To:     ulf.hansson@...aro.org
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        gaoce123@...il.com
Subject: [PATCH] mmc: core: Add error check to avoid kernel panic caused by NULL pointer

If __mmc_start_req(host, mrq) fails with error, the mrq->cmd->mrq will
be NULL. This will cause kernel panic in the following
mmc_wait_for_req_done(host, mrq). Add error check to cancle unnecessary
mmc_wait_for_req_done(host, mrq) if __mmc_start_req(host, mrq) fails.

Signed-off-by: Corey Gao <gaoce123@...il.com>
---
 drivers/mmc/core/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 2553d903a82b..b13b484e64aa 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -734,9 +734,11 @@ EXPORT_SYMBOL(mmc_start_req);
  */
 void mmc_wait_for_req(struct mmc_host *host, struct mmc_request *mrq)
 {
-	__mmc_start_req(host, mrq);
+	int err;
 
-	if (!mrq->cap_cmd_during_tfr)
+	err = __mmc_start_req(host, mrq);
+
+	if (!mrq->cap_cmd_during_tfr && !err)
 		mmc_wait_for_req_done(host, mrq);
 }
 EXPORT_SYMBOL(mmc_wait_for_req);
-- 
2.17.1