From: Thomas Weißschuh <thomas@t-8ch.de>
Date: Sat, 30 Sep 2023 21:56:46 +0000 (+0200)
Subject: libblkid: (probe) allow superblock offset from end of device
X-Git-Tag: v2.40-rc1~221^2~3
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2816a817149c792fa836d9ab06b64934aee8ac33;p=thirdparty%2Futil-linux.git

libblkid: (probe) allow superblock offset from end of device

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

diff --git a/libblkid/src/probe.c b/libblkid/src/probe.c
index c5d77a17fb..d55cf5eb17 100644
--- a/libblkid/src/probe.c
+++ b/libblkid/src/probe.c
@@ -1200,12 +1200,18 @@ int blkid_probe_set_dimension(blkid_probe pr, uint64_t off, uint64_t size)
 
 const unsigned char *blkid_probe_get_sb_buffer(blkid_probe pr, const struct blkid_idmag *mag, size_t size)
 {
-	uint64_t hint_offset;
+	uint64_t hint_offset, off;
 
-	if (!mag->hoff || blkid_probe_get_hint(pr, mag->hoff, &hint_offset) < 0)
-		hint_offset = 0;
+	if (mag->kboff >= 0) {
+		if (!mag->hoff || blkid_probe_get_hint(pr, mag->hoff, &hint_offset) < 0)
+			hint_offset = 0;
+
+		off = hint_offset + (mag->kboff << 10);
+	} else {
+		off = pr->size - (-mag->kboff << 10);
+	}
 
-	return blkid_probe_get_buffer(pr, hint_offset + (mag->kboff << 10), size);
+	return blkid_probe_get_buffer(pr, off, size);
 }
 
 /*
@@ -1227,7 +1233,7 @@ int blkid_probe_get_idmag(blkid_probe pr, const struct blkid_idinfo *id,
 	/* try to detect by magic string */
 	while(mag && mag->magic) {
 		const unsigned char *buf;
-		uint64_t kboff;
+		long kboff;
 		uint64_t hint_offset;
 
 		if (!mag->hoff || blkid_probe_get_hint(pr, mag->hoff, &hint_offset) < 0)
@@ -1244,7 +1250,10 @@ int blkid_probe_get_idmag(blkid_probe pr, const struct blkid_idinfo *id,
 		else
 			kboff = ((mag->zonenum * pr->zone_size) >> 10) + mag->kboff_inzone;
 
-		off = hint_offset + ((kboff + (mag->sboff >> 10)) << 10);
+		if (kboff >= 0)
+			off = hint_offset + ((kboff + (mag->sboff >> 10)) << 10);
+		else
+			off = pr->size - (-kboff << 10);
 		buf = blkid_probe_get_buffer(pr, off, 1024);
 
 		if (!buf && errno)
@@ -1253,7 +1262,7 @@ int blkid_probe_get_idmag(blkid_probe pr, const struct blkid_idinfo *id,
 		if (buf && !memcmp(mag->magic,
 				buf + (mag->sboff & 0x3ff), mag->len)) {
 
-			DBG(LOWPROBE, ul_debug("\tmagic sboff=%u, kboff=%" PRIu64,
+			DBG(LOWPROBE, ul_debug("\tmagic sboff=%u, kboff=%ld",
 				mag->sboff, kboff));
 			if (offset)
 				*offset = off + (mag->sboff & 0x3ff);