[PATCH RFC] brcmfmac: sanitize DMI strings v2

[Victor Bravo <1905@spmblk.com>]

Sanitize DMI strings in brcmfmac driver to make resulting filenames
contain only safe characters. This version replaces all non-printable
characters incl. delete (0-31, 127-255), spaces and slashes with
underscores.

This change breaks backward compatibility, but adds control over strings
passed to firmware loader and compatibility with CONFIG_EXTRA_FIRMWARE
which doesn't support spaces in filenames.

Changes from v1: don't revert fresh commit by someone else

Signed-off-by: Victor Bravo <1905@spmblk.com>

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/dmi.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/dmi.c
index 7535cb0d4ac0..84571e09b465 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/dmi.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/dmi.c
@@ -23,6 +23,14 @@
 /* The DMI data never changes so we can use a static buf for this */
 static char dmi_board_type[128];
 
+/* Array of 128 bits representing 7-bit characters allowed in DMI strings. */
+static unsigned char brcmf_dmi_allowed_chars[] = {
+	0x00, 0x00, 0x00, 0x00, 0xfe, 0x7f, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f
+};
+
+#define BRCMF_DMI_SAFE_CHAR '_'
+
 struct brcmf_dmi_data {
 	u32 chip;
 	u32 chiprev;
@@ -99,6 +107,15 @@ static const struct dmi_system_id dmi_platform_data[] = {
 	{}
 };
 
+void brcmf_dmi_sanitize(char *dst, const unsigned char *allowed, char safe)
+{
+	while (*dst) {
+		if ((*dst < 0) || !(allowed[*dst / 8] & (1 << (*dst % 8))))
+			*dst = safe;
+		dst++;
+	}
+}
+
 void brcmf_dmi_probe(struct brcmf_mp_device *settings, u32 chip, u32 chiprev)
 {
 	const struct dmi_system_id *match;
@@ -126,6 +143,9 @@ void brcmf_dmi_probe(struct brcmf_mp_device *settings, u32 chip, u32 chiprev)
 	if (sys_vendor && product_name) {
 		snprintf(dmi_board_type, sizeof(dmi_board_type), "%s-%s",
 			 sys_vendor, product_name);
+		brcmf_dmi_sanitize(dmi_board_type,
+				   brcmf_dmi_allowed_chars,
+				   BRCMF_DMI_SAFE_CHAR);
 		settings->board_type = dmi_board_type;
 	}
 }