From: Thomas Weißschuh <thomas@t-8ch.de>
Date: Fri, 12 Jan 2024 07:50:14 +0000 (+0100)
Subject: libblkid: (drbd) validate zero padding
X-Git-Tag: v2.40-rc1~45^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4ee2db2a221f6404f9fe9470da7c384a25cceea3;p=thirdparty%2Futil-linux.git

libblkid: (drbd) validate zero padding

This should reduce false-positives.

See #2701.

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---

diff --git a/libblkid/src/superblocks/drbd.c b/libblkid/src/superblocks/drbd.c
index baead1d78a..b425906927 100644
--- a/libblkid/src/superblocks/drbd.c
+++ b/libblkid/src/superblocks/drbd.c
@@ -70,9 +70,8 @@ struct md_on_disk_08 {
 	uint32_t bm_bytes_per_bit;
 	uint32_t reserved_u32[4];
 
-	/* Unnecessary for libblkid **
-	 * char reserved[8 * 512 - (8*(UI_SIZE+3)+4*11)];
-	 */
+	unsigned char padding_start[0];
+	unsigned char padding_end[0] __attribute__((aligned(4096)));
 };
 
 /*
@@ -118,12 +117,21 @@ struct meta_data_on_disk_9 {
 	struct peer_dev_md_on_disk_9 peers[DRBD_PEERS_MAX];
 	uint64_t history_uuids[HISTORY_UUIDS];
 
-	/* Unnecessary for libblkid **
-	 * char padding[0] __attribute__((aligned(4096)));
-	 */
+	unsigned char padding_start[0];
+	unsigned char padding_end[0] __attribute__((aligned(4096)));
 } __attribute__((packed));
 
 
+static int is_zero_padded(const unsigned char *padding_start,
+			  const unsigned char *padding_end)
+{
+	for (; padding_start < padding_end; padding_start++) {
+		if (*padding_start != 0)
+			return 0;
+	}
+	return 1;
+}
+
 static int probe_drbd_84(blkid_probe pr, const struct blkid_idmag *mag)
 {
 	struct md_on_disk_08 *md;
@@ -132,6 +140,10 @@ static int probe_drbd_84(blkid_probe pr, const struct blkid_idmag *mag)
 	if (!md)
 		return errno ? -errno : 1;
 
+	if (!is_zero_padded(member_ptr(md, padding_start),
+			    member_ptr(md, padding_end)))
+		return 1;
+
 	/*
 	 * DRBD does not have "real" uuids; the following resembles DRBD's
 	 * notion of uuids (64 bit, see struct above)
@@ -153,6 +165,10 @@ static int probe_drbd_90(blkid_probe pr, const struct blkid_idmag *mag)
 	if (!md)
 		return errno ? -errno : 1;
 
+	if (!is_zero_padded(member_ptr(md, padding_start),
+			    member_ptr(md, padding_end)))
+		return 1;
+
 	/*
 	 * DRBD does not have "real" uuids; the following resembles DRBD's
 	 * notion of uuids (64 bit, see struct above)