[PATCH] mmc: core: Sanitize CID product names

Some devices return nonprintable or non-ASCII bytes in CID product
names. One example device reports H8G4a followed by 0x92.

This led to downstream problems like in pyparted[1] or systemd[2] where
the consumers assumed the names were effectively ASCII-like.

Commit 3b791214c8bc ("mmc: core: Trim trailing whitespace from card
product names") established parse time normalization for CID names.
Extend that normalization by replacing bytes outside printable ASCII
with a question mark after the existing whitespace trimming.

The raw CID remains untouched. This patch doesn't change the lengths of
the sanitized names.

[1] https://github.com/dcantrell/pyparted/issues/76 (already fixed)
[2] https://github.com/systemd/systemd/issues/42930

Assisted-by: Codex:GPT-5
Signed-off-by: Jakub Stasiak <[email protected]>
---
 drivers/mmc/core/core.c | 21 +++++++++++++++++++++
 drivers/mmc/core/core.h |  1 +
 drivers/mmc/core/mmc.c  |  3 +--
 drivers/mmc/core/sd.c   |  3 +--
 4 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 29e80e5f928e..0de2a0133f13 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -8,6 +8,7 @@
  *  MMCv4 support Copyright (C) 2006 Philip Langdale, All Rights Reserved.
  */
 #include <linux/module.h>
+#include <linux/ctype.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/completion.h>
@@ -23,6 +24,7 @@
 #include <linux/fault-inject.h>
 #include <linux/random.h>
 #include <linux/slab.h>
+#include <linux/string.h>
 #include <linux/of.h>
 
 #include <linux/mmc/card.h>
@@ -52,6 +54,25 @@
 
 static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
 
+/**
+ * mmc_sanitize_cid_name() - sanitize a CID product name in place
+ * @name: NUL-terminated CID product name to sanitize
+ *
+ * Trim trailing whitespace and replace bytes outside printable ASCII with '?'.
+ */
+void mmc_sanitize_cid_name(char *name)
+{
+	char *p;
+
+	/* some product names may include trailing whitespace */
+	strim(name);
+
+	/* Keep product names safe for sysfs and uevent consumers. */
+	for (p = name; *p; p++)
+		if (!isascii(*p) || !isprint(*p))
+			*p = '?';
+}
+
 /*
  * Enabling software CRCs on the data blocks can be a significant (30%)
  * performance cost, and for other reasons may not always be desired.
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index a028b48be164..0ec5ad66fb7c 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -41,6 +41,7 @@ struct device_node *mmc_of_find_child_device(struct mmc_host *host,
 		unsigned func_num);
 
 void mmc_init_erase(struct mmc_card *card);
+void mmc_sanitize_cid_name(char *name);
 
 void mmc_set_chip_select(struct mmc_host *host, int mode);
 void mmc_set_clock(struct mmc_host *host, unsigned int hz);
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 05444ecf3909..dca76be9f0dd 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -117,8 +117,7 @@ static int mmc_decode_cid(struct mmc_card *card)
 		return -EINVAL;
 	}
 
-	/* some product names include trailing whitespace */
-	strim(card->cid.prod_name);
+	mmc_sanitize_cid_name(card->cid.prod_name);
 
 	return 0;
 }
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index c763efb10f64..7dc2b791f44c 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -97,8 +97,7 @@ void mmc_decode_cid(struct mmc_card *card)
 
 	card->cid.year += 2000; /* SD cards year offset */
 
-	/* some product names may include trailing whitespace */
-	strim(card->cid.prod_name);
+	mmc_sanitize_cid_name(card->cid.prod_name);
 }
 
 /*
-- 
2.55.0