From: Karel Zak <kzak@redhat.com>
Date: Thu, 4 Feb 2010 21:19:38 +0000 (+0100)
Subject: libblkid: don't return error on empty files
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8c9cd53708c0aca63d9a8f507cb2eddb0478bcc7;p=util-linux

libblkid: don't return error on empty files

Currently, the library does not allow to initialize blkid_probe if the
file (or block device) is empty. The empty file is reported as an
error. That's wrong. The empty file should be interpreted as a file
without any FS or PT. It means that

	blkid_do_{probe,safeprobe,fullprobe}()

have to return 1 ("nothing").

Reported-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/shlibs/blkid/src/partitions/partitions.c b/shlibs/blkid/src/partitions/partitions.c
index 154365d7..e8d03113 100644
--- a/shlibs/blkid/src/partitions/partitions.c
+++ b/shlibs/blkid/src/partitions/partitions.c
@@ -505,7 +505,7 @@ static int idinfo_probe(blkid_probe pr, const struct blkid_idinfo *id)
 	int hasmag = 0;
 	int rc = 1;		/* = nothing detected */
 
-	if (id->minsz && id->minsz > pr->size)
+	if (pr->size <= 0 || (id->minsz && id->minsz > pr->size))
 		goto nothing;	/* the device is too small */
 
 	mag = id->magics ? &id->magics[0] : NULL;
diff --git a/shlibs/blkid/src/probe.c b/shlibs/blkid/src/probe.c
index 91366851..e7845816 100644
--- a/shlibs/blkid/src/probe.c
+++ b/shlibs/blkid/src/probe.c
@@ -289,7 +289,7 @@ void *blkid_probe_get_binary_data(blkid_probe pr, struct blkid_chain *chn)
 {
 	int rc;
 
-	if (!pr && !chn)
+	if (!pr || !chn)
 		return NULL;
 
 	pr->cur_chain = chn;
@@ -465,6 +465,9 @@ unsigned char *blkid_probe_get_buffer(blkid_probe pr,
 	struct list_head *p;
 	struct blkid_bufinfo *bf = NULL;
 
+	if (pr->size <= 0)
+		return NULL;
+
 	list_for_each(p, &pr->buffers) {
 		struct blkid_bufinfo *x =
 				list_entry(p, struct blkid_bufinfo, bufs);
@@ -605,8 +608,6 @@ int blkid_probe_set_device(blkid_probe pr, int fd,
 		pr->size -= pr->off;
 	}
 
-	if (!pr->size)
-		goto err;
 	DBG(DEBUG_LOWPROBE, printf("ready for low-probing, offset=%zd, size=%zd\n",
 				pr->off, pr->size));
 
@@ -648,6 +649,10 @@ int blkid_probe_set_dimension(blkid_probe pr,
 
 	pr->off = off;
 	pr->size = size;
+	pr->flags &= ~BLKID_TINY_DEV;
+
+	if (pr->size <= 1440 * 1024 && !S_ISCHR(pr->mode))
+		pr->flags |= BLKID_TINY_DEV;
 
 	blkid_probe_reset_buffer(pr);
 
diff --git a/shlibs/blkid/src/superblocks/superblocks.c b/shlibs/blkid/src/superblocks/superblocks.c
index 689f31bd..932701a8 100644
--- a/shlibs/blkid/src/superblocks/superblocks.c
+++ b/shlibs/blkid/src/superblocks/superblocks.c
@@ -310,7 +310,7 @@ static int superblocks_probe(blkid_probe pr, struct blkid_chain *chn)
 		printf("--> starting probing loop [SUBLKS idx=%d]\n",
 		chn->idx));
 
-	if (pr->size <= 1024 && !S_ISCHR(pr->mode))
+	if (pr->size <= 0 || (pr->size <= 1024 && !S_ISCHR(pr->mode)))
 		/* Ignore very very small block devices or regular files (e.g.
 		 * extended partitions). Note that size of the UBI char devices
 		 * is 1 byte */