linux-kernel - [PATCH 5.4 08/61] mtd: cfi_cmdset_0002: fix crash when erasing/writing AMD cards

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Date:   Tue, 24 Aug 2021 13:00:13 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Andreas Persson <andreasp56@...look.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 5.4 08/61] mtd: cfi_cmdset_0002: fix crash when erasing/writing AMD cards

From: Andreas Persson <andreasp56@...look.com>

commit 2394e628738933aa014093d93093030f6232946d upstream.

Erasing an AMD linear flash card (AM29F016D) crashes after the first
sector has been erased. Likewise, writing to it crashes after two bytes
have been written. The reason is a missing check for a null pointer -
the cmdset_priv field is not set for this type of card.

Fixes: 4844ef80305d ("mtd: cfi_cmdset_0002: Add support for polling status register")
Signed-off-by: Andreas Persson <andreasp56@...look.com>
Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
Link: https://lore.kernel.org/linux-mtd/DB6P189MB05830B3530B8087476C5CFE4C1159@DB6P189MB0583.EURP189.PROD.OUTLOOK.COM
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/mtd/chips/cfi_cmdset_0002.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
index c8b9ab40a102..9c98ddef0097 100644
--- a/drivers/mtd/chips/cfi_cmdset_0002.c
+++ b/drivers/mtd/chips/cfi_cmdset_0002.c
@@ -119,7 +119,7 @@ static int cfi_use_status_reg(struct cfi_private *cfi)
 	struct cfi_pri_amdstd *extp = cfi->cmdset_priv;
 	u8 poll_mask = CFI_POLL_STATUS_REG | CFI_POLL_DQ;
 
-	return extp->MinorVersion >= '5' &&
+	return extp && extp->MinorVersion >= '5' &&
 		(extp->SoftwareFeatures & poll_mask) == CFI_POLL_STATUS_REG;
 }
 
-- 
2.30.2