linux-kernel - [PATCH 4.14 46/95] mmc: block: Ensure that debugfs files are removed

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Message-Id: <20171204160048.023444954@linuxfoundation.org>
Date:   Mon,  4 Dec 2017 17:00:10 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Adrian Hunter <adrian.hunter@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 4.14 46/95] mmc: block: Ensure that debugfs files are removed

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Adrian Hunter <adrian.hunter@...el.com>

commit f9f0da98819503b06b35e61869d18cf3a8cd3323 upstream.

The card is not necessarily being removed, but the debugfs files must be
removed when the driver is removed, otherwise they will continue to exist
after unbinding the card from the driver. e.g.

  # echo "mmc1:0001" > /sys/bus/mmc/drivers/mmcblk/unbind
  # cat /sys/kernel/debug/mmc1/mmc1\:0001/ext_csd
  [  173.634584] BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
  [  173.643356] IP: mmc_ext_csd_open+0x5e/0x170

A complication is that the debugfs_root may have already been removed, so
check for that too.

Fixes: 627c3ccfb46a ("mmc: debugfs: Move block debugfs into block module")
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mmc/core/block.c   |   44 +++++++++++++++++++++++++++++++++++++-------
 drivers/mmc/core/debugfs.c |    1 +
 2 files changed, 38 insertions(+), 7 deletions(-)

--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -119,6 +119,10 @@ struct mmc_blk_data {
 	struct device_attribute force_ro;
 	struct device_attribute power_ro_lock;
 	int	area_type;
+
+	/* debugfs files (only in main mmc_blk_data) */
+	struct dentry *status_dentry;
+	struct dentry *ext_csd_dentry;
 };
 
 static DEFINE_MUTEX(open_lock);
@@ -2417,7 +2421,7 @@ static const struct file_operations mmc_
 	.llseek		= default_llseek,
 };
 
-static int mmc_blk_add_debugfs(struct mmc_card *card)
+static int mmc_blk_add_debugfs(struct mmc_card *card, struct mmc_blk_data *md)
 {
 	struct dentry *root;
 
@@ -2427,28 +2431,53 @@ static int mmc_blk_add_debugfs(struct mm
 	root = card->debugfs_root;
 
 	if (mmc_card_mmc(card) || mmc_card_sd(card)) {
-		if (!debugfs_create_file("status", S_IRUSR, root, card,
-					 &mmc_dbg_card_status_fops))
+		md->status_dentry =
+			debugfs_create_file("status", S_IRUSR, root, card,
+					    &mmc_dbg_card_status_fops);
+		if (!md->status_dentry)
 			return -EIO;
 	}
 
 	if (mmc_card_mmc(card)) {
-		if (!debugfs_create_file("ext_csd", S_IRUSR, root, card,
-					 &mmc_dbg_ext_csd_fops))
+		md->ext_csd_dentry =
+			debugfs_create_file("ext_csd", S_IRUSR, root, card,
+					    &mmc_dbg_ext_csd_fops);
+		if (!md->ext_csd_dentry)
 			return -EIO;
 	}
 
 	return 0;
 }
 
+static void mmc_blk_remove_debugfs(struct mmc_card *card,
+				   struct mmc_blk_data *md)
+{
+	if (!card->debugfs_root)
+		return;
+
+	if (!IS_ERR_OR_NULL(md->status_dentry)) {
+		debugfs_remove(md->status_dentry);
+		md->status_dentry = NULL;
+	}
+
+	if (!IS_ERR_OR_NULL(md->ext_csd_dentry)) {
+		debugfs_remove(md->ext_csd_dentry);
+		md->ext_csd_dentry = NULL;
+	}
+}
 
 #else
 
-static int mmc_blk_add_debugfs(struct mmc_card *card)
+static int mmc_blk_add_debugfs(struct mmc_card *card, struct mmc_blk_data *md)
 {
 	return 0;
 }
 
+static void mmc_blk_remove_debugfs(struct mmc_card *card,
+				   struct mmc_blk_data *md)
+{
+}
+
 #endif /* CONFIG_DEBUG_FS */
 
 static int mmc_blk_probe(struct mmc_card *card)
@@ -2488,7 +2517,7 @@ static int mmc_blk_probe(struct mmc_card
 	}
 
 	/* Add two debugfs entries */
-	mmc_blk_add_debugfs(card);
+	mmc_blk_add_debugfs(card, md);
 
 	pm_runtime_set_autosuspend_delay(&card->dev, 3000);
 	pm_runtime_use_autosuspend(&card->dev);
@@ -2514,6 +2543,7 @@ static void mmc_blk_remove(struct mmc_ca
 {
 	struct mmc_blk_data *md = dev_get_drvdata(&card->dev);
 
+	mmc_blk_remove_debugfs(card, md);
 	mmc_blk_remove_parts(card, md);
 	pm_runtime_get_sync(&card->dev);
 	mmc_claim_host(card->host);
--- a/drivers/mmc/core/debugfs.c
+++ b/drivers/mmc/core/debugfs.c
@@ -314,4 +314,5 @@ err:
 void mmc_remove_card_debugfs(struct mmc_card *card)
 {
 	debugfs_remove_recursive(card->debugfs_root);
+	card->debugfs_root = NULL;
 }