linux-kernel - [PATCH] libata: fix using DMA buffers on stack

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Message-Id: <20190328121925.15488-1-raymondpangxd@gmail.com>
Date:   Thu, 28 Mar 2019 12:19:25 +0000
From:   raymond pang <raymondpangxd@...il.com>
To:     axboe@...nel.dk
Cc:     linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] libata: fix using DMA buffers on stack

When CONFIG_VMAP_STACK=y, __pa() returns incorrect physical address for
a stack virtual address. Stack DMA buffers must be avoided.

Signed-off-by: raymond pang <raymondpangxd@...il.com>
---
 drivers/ata/libata-zpodd.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/drivers/ata/libata-zpodd.c b/drivers/ata/libata-zpodd.c
index b3ed8f995..173e6f2dd 100644
--- a/drivers/ata/libata-zpodd.c
+++ b/drivers/ata/libata-zpodd.c
@@ -52,38 +52,52 @@ static int eject_tray(struct ata_device *dev)
 /* Per the spec, only slot type and drawer type ODD can be supported */
 static enum odd_mech_type zpodd_get_mech_type(struct ata_device *dev)
 {
-	char buf[16];
+	char *buf;
 	unsigned int ret;
-	struct rm_feature_desc *desc = (void *)(buf + 8);
+	struct rm_feature_desc *desc;
 	struct ata_taskfile tf;
 	static const char cdb[] = {  GPCMD_GET_CONFIGURATION,
 			2,      /* only 1 feature descriptor requested */
 			0, 3,   /* 3, removable medium feature */
 			0, 0, 0,/* reserved */
-			0, sizeof(buf),
+			0, 16,
 			0, 0, 0,
 	};

+	buf = kzalloc(16, GFP_KERNEL);
+	if (!buf)
+		return ODD_MECH_TYPE_UNSUPPORTED;
+	desc = (void *)(buf + 8);
+
 	ata_tf_init(dev, &tf);
 	tf.flags = ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
 	tf.command = ATA_CMD_PACKET;
 	tf.protocol = ATAPI_PROT_PIO;
-	tf.lbam = sizeof(buf);
+	tf.lbam = 16;

 	ret = ata_exec_internal(dev, &tf, cdb, DMA_FROM_DEVICE,
-				buf, sizeof(buf), 0);
-	if (ret)
+				buf, 16, 0);
+	if (ret) {
+		kfree(buf);
 		return ODD_MECH_TYPE_UNSUPPORTED;
+	}

-	if (be16_to_cpu(desc->feature_code) != 3)
+	if (be16_to_cpu(desc->feature_code) != 3) {
+		kfree(buf);
 		return ODD_MECH_TYPE_UNSUPPORTED;
+	}

-	if (desc->mech_type == 0 && desc->load == 0 && desc->eject == 1)
+	if (desc->mech_type == 0 && desc->load == 0 && desc->eject == 1) {
+		kfree(buf);
 		return ODD_MECH_TYPE_SLOT;
-	else if (desc->mech_type == 1 && desc->load == 0 && desc->eject == 1)
+	} else if (desc->mech_type == 1 && desc->load == 0 &&
+		   desc->eject == 1) {
+		kfree(buf);
 		return ODD_MECH_TYPE_DRAWER;
-	else
+	} else {
+		kfree(buf);
 		return ODD_MECH_TYPE_UNSUPPORTED;
+	}
 }

 /* Test if ODD is zero power ready by sense code */
--
2.19.1