[PATCH 4/4] libmultipath: fix over-long NVME WWIDs

[Martin Wilck]

Fix for NVME wwids looking like this:
nvme.0000-3163653363666438366239656630386200-4c696e75780000000000000000000000000000000000000000000000000000000000000000000000-00000002
which are encountered in some combinations of Linux NVME host and target,
where the 2nd field represents the serial number (SN) and the 3rd the
model number (MN).

The device mapper allows map names only up to 128 characters.
Strip the "00" sequences at the end of the serial and model field,
they are hex-encoded 0-bytes which are forbidden by the NVME spec
anyway.

Signed-off-by: Martin Wilck <mwilck at suse.com>
---
 libmultipath/discovery.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
index 9951af84..f46b9b17 100644
--- a/libmultipath/discovery.c
+++ b/libmultipath/discovery.c
@@ -1598,6 +1598,82 @@ get_prio (struct path * pp)
 	return 0;
 }
 
+/*
+ * Mangle string of length *len starting at start
+ * by removing character sequence "00" (hex for a 0 byte),
+ * starting at end, backwards.
+ * Changes the value of *len if characters were removed.
+ * Returns a pointer to the position where "end" was moved to.
+ */
+static char
+*skip_zeroes_backward(char* start, int *len, char *end)
+{
+	char *p = end;
+
+	while (p >= start + 2 && *(p - 1) == '0' && *(p - 2) == '0')
+		p -= 2;
+
+	if (p == end)
+		return p;
+
+	memmove(p, end, start + *len + 1 - end);
+	*len -= end - p;
+
+	return p;
+}
+
+/*
+ * Fix for NVME wwids looking like this:
+ * nvme.0000-3163653363666438366239656630386200-4c696e75780000000000000000000000000000000000000000000000000000000000000000000000-00000002
+ * which are encountered in some combinations of Linux NVME host and target.
+ * The '00' are hex-encoded 0-bytes which are forbidden in the serial (SN)
+ * and model (MN) fields. Discard them.
+ * If a WWID of the above type is found, sets pp->wwid and returns a value > 0.
+ * Otherwise, returns 0.
+ */
+static int
+fix_broken_nvme_wwid(struct path *pp, const char *value, int size)
+{
+	static const char _nvme[] = "nvme.";
+	int len, i;
+	char mangled[256];
+	char *p;
+
+	len = strlen(value);
+	if (len >= sizeof(mangled) || len + 1 < size)
+		return 0;
+
+	/* Check that value starts with "nvme.%04x-" */
+	if (memcmp(value, _nvme, sizeof(_nvme) - 1) || value[9] != '-')
+		return 0;
+	for (i = 5; i < 9; i++)
+		if (!isxdigit(value[i]))
+			return 0;
+
+	memcpy(mangled, value, len + 1);
+
+	/* search end of "model" part and strip trailing '00' */
+	p = memrchr(mangled, '-', len);
+	if (p == NULL)
+		return 0;
+
+	p = skip_zeroes_backward(mangled, &len, p);
+
+	/* search end of "serial" part */
+	p = memrchr(mangled, '-', p - mangled);
+	if (p == NULL || memrchr(mangled, '-', p - mangled) != mangled + 9)
+	    /* We expect exactly 3 '-' in the value */
+		return 0;
+
+	p = skip_zeroes_backward(mangled, &len, p);
+	if (len >= size)
+		return 0;
+
+	memcpy(pp->wwid, mangled, len + 1);
+	condlog(2, "%s: over-long WWID shortened to %s", pp->dev, pp->wwid);
+	return len;
+}
+
 static int
 get_udev_uid(struct path * pp, char *uid_attribute, struct udev_device *udev)
 {
@@ -1609,6 +1685,9 @@ get_udev_uid(struct path * pp, char *uid_attribute, struct udev_device *udev)
 		value = getenv(uid_attribute);
 	if (value && strlen(value)) {
 		if (strlen(value) + 1 > WWID_SIZE) {
+			len = fix_broken_nvme_wwid(pp, value, WWID_SIZE);
+			if (len > 0)
+				return len;
 			condlog(0, "%s: wwid overflow", pp->dev);
 			len = WWID_SIZE;
 		} else {
-- 
2.13.2