From: Thomas Weißschuh <thomas@t-8ch.de>
Date: Sun, 20 Nov 2022 04:50:16 +0000 (+0100)
Subject: libblkid: dos: ignore exfat superblocks
X-Git-Tag: v2.39-rc1~415^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8a0f04e614276ef97f66f52b32f10dd56df09e40;p=thirdparty%2Futil-linux.git

libblkid: dos: ignore exfat superblocks
---

diff --git a/libblkid/src/partitions/dos.c b/libblkid/src/partitions/dos.c
index 6e758ecaaa..5c7718c3e2 100644
--- a/libblkid/src/partitions/dos.c
+++ b/libblkid/src/partitions/dos.c
@@ -19,6 +19,8 @@
 
 /* see superblocks/vfat.c */
 extern int blkid_probe_is_vfat(blkid_probe pr);
+/* see superblocks/exfat.c */
+extern int blkid_probe_is_exfat(blkid_probe pr);
 
 static const struct dos_subtypes {
 	unsigned char type;
@@ -218,7 +220,7 @@ static int probe_dos_pt(blkid_probe pr,
 	 * either the boot sector of a FAT filesystem or a DOS-type
 	 * partition table.
 	 */
-	if (blkid_probe_is_vfat(pr) == 1) {
+	if (blkid_probe_is_vfat(pr) == 1 || blkid_probe_is_exfat(pr) == 1) {
 		DBG(LOWPROBE, ul_debug("probably FAT -- ignore"));
 		goto nothing;
 	}
diff --git a/libblkid/src/superblocks/exfat.c b/libblkid/src/superblocks/exfat.c
index 4b6414fde9..e760604908 100644
--- a/libblkid/src/superblocks/exfat.c
+++ b/libblkid/src/superblocks/exfat.c
@@ -158,26 +158,66 @@ static int exfat_validate_checksum(blkid_probe pr,
 	return 1;
 }
 
-static int probe_exfat(blkid_probe pr, const struct blkid_idmag *mag)
+static int exfat_valid_superblock(blkid_probe pr, const struct exfat_super_block *sb)
 {
-	struct exfat_super_block *sb;
-	struct exfat_entry_label *label;
-
-	sb = blkid_probe_get_sb(pr, mag, struct exfat_super_block);
-	if (!sb || !CLUSTER_SIZE(sb))
-		return errno ? -errno : BLKID_PROBE_NONE;
-
 	if (le16_to_cpu(sb->BootSignature) != 0xAA55)
-		return BLKID_PROBE_NONE;
+		return 0;
+
+	if (!CLUSTER_SIZE(sb))
+		return 0;
 
 	if (memcmp(sb->JumpBoot, "\xEB\x76\x90", 3) != 0)
-		return BLKID_PROBE_NONE;
+		return 0;
 
 	for (size_t i = 0; i < sizeof(sb->MustBeZero); i++)
 		if (sb->MustBeZero[i] != 0x00)
-			return BLKID_PROBE_NONE;
+			return 0;
 
 	if (!exfat_validate_checksum(pr, sb))
+		return 0;
+
+	return 1;
+}
+
+/* function prototype to avoid warnings (duplicate in partitions/dos.c) */
+extern int blkid_probe_is_exfat(blkid_probe pr);
+
+/*
+ * This function is used by MBR partition table parser to avoid
+ * misinterpretation of exFAT filesystem.
+ */
+int blkid_probe_is_exfat(blkid_probe pr)
+{
+	struct exfat_super_block *sb;
+	const struct blkid_idmag *mag = NULL;
+	int rc;
+
+	rc = blkid_probe_get_idmag(pr, &vfat_idinfo, NULL, &mag);
+	if (rc < 0)
+		return rc;	/* error */
+	if (rc != BLKID_PROBE_OK || !mag)
+		return 0;
+
+	sb = blkid_probe_get_sb(pr, mag, struct exfat_super_block);
+	if (!sb)
+		return 0;
+
+	if (memcmp(sb->FileSystemName, "EXFAT   ", 8) != 0)
+		return 0;
+
+	return exfat_valid_superblock(pr, sb);
+}
+
+static int probe_exfat(blkid_probe pr, const struct blkid_idmag *mag)
+{
+	struct exfat_super_block *sb;
+	struct exfat_entry_label *label;
+
+	sb = blkid_probe_get_sb(pr, mag, struct exfat_super_block);
+	if (!sb)
+		return errno ? -errno : BLKID_PROBE_NONE;
+
+	if (!exfat_valid_superblock(pr, sb))
 		return BLKID_PROBE_NONE;
 
 	label = find_label(pr, sb);