linux-ext4 - [PATCH 48/47] misc: fix infinite loop when finding the start of the hugefile start range

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Message-ID: <20141112224329.GI10043@birch.djwong.org>
Date:	Wed, 12 Nov 2014 14:43:29 -0800
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	tytso@....edu, darrick.wong@...cle.com
Cc:	linux-ext4@...r.kernel.org
Subject: [PATCH 48/47] misc: fix infinite loop when finding the start of the
 hugefile start range

When looking for the start of the hugefile range, the 'next' variable
is incorrectly decremented.  If we happened to find a single free
block, the effect of this decrement is that blk == next, which means
that we never modify the loop control variable, so get_start_block
never returns.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 misc/mk_hugefiles.c           |    1 -
 tests/m_hugefile_slack/expect |   18 ++++++++++++
 tests/m_hugefile_slack/name   |    1 +
 tests/m_hugefile_slack/script |   61 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 80 insertions(+), 1 deletion(-)
 create mode 100644 tests/m_hugefile_slack/expect
 create mode 100644 tests/m_hugefile_slack/name
 create mode 100644 tests/m_hugefile_slack/script

diff --git a/misc/mk_hugefiles.c b/misc/mk_hugefiles.c
index 3e4274c..230844f 100644
--- a/misc/mk_hugefiles.c
+++ b/misc/mk_hugefiles.c
@@ -437,7 +437,6 @@ static blk64_t get_start_block(ext2_filsys fs, blk64_t slack)
 						blk, last_blk, &next);
 		if (retval)
 			next = last_blk;
-		next--;
 
 		if (next - blk > slack) {
 			blk += slack;
diff --git a/tests/m_hugefile_slack/expect b/tests/m_hugefile_slack/expect
new file mode 100644
index 0000000..96a628a
--- /dev/null
+++ b/tests/m_hugefile_slack/expect
@@ -0,0 +1,18 @@
+tune2fs test
+Creating filesystem with 786432 1k blocks and 98304 inodes
+Superblock backups stored on blocks: 
+	8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409, 663553
+
+Allocating group tables:      .....done                            
+Writing inode tables:      .....done                            
+Creating journal (16384 blocks): done
+Creating 6368 huge file(s) with 117 blocks each: done
+Writing superblocks and filesystem accounting information:      .....done
+
+Pass 1: Checking inodes, blocks, and sizes
+Pass 2: Checking directory structure
+Pass 3: Checking directory connectivity
+Pass 4: Checking reference counts
+Pass 5: Checking group summary information
+
+Exit status is 0
diff --git a/tests/m_hugefile_slack/name b/tests/m_hugefile_slack/name
new file mode 100644
index 0000000..51cef19
--- /dev/null
+++ b/tests/m_hugefile_slack/name
@@ -0,0 +1 @@
+trigger infinite loop when creating hugefiles with a lot of slack
diff --git a/tests/m_hugefile_slack/script b/tests/m_hugefile_slack/script
new file mode 100644
index 0000000..96f5ec5
--- /dev/null
+++ b/tests/m_hugefile_slack/script
@@ -0,0 +1,61 @@
+if test -x $RESIZE2FS_EXE -a -x $DEBUGFS_EXE; then
+
+FSCK_OPT=-fn
+OUT=$test_name.log
+EXP=$test_dir/expect
+CONF=$TMPFILE.conf
+
+#gzip -d < $EXP.gz > $EXP
+
+cat > $CONF << ENDL
+[fs_types]
+	ext4h = {
+		features = has_journal,extent,huge_file,uninit_bg,dir_nlink,extra_isize,sparse_super,filetype,dir_index,ext_attr,^resize_inode,^meta_bg,^flex_bg,metadata_csum,64bit
+		blocksize = 1024
+		inode_size = 256
+		make_hugefiles = true
+		hugefiles_dir = /
+		hugefiles_slack = 12000K
+		hugefiles_name = aaaaa
+		hugefiles_digits = 4
+		hugefiles_size = 117K
+		zero_hugefiles = false
+	}
+ENDL
+
+echo "tune2fs test" > $OUT
+
+MKE2FS_CONFIG=$CONF $MKE2FS -F -T ext4h -I 128 $TMPFILE 786432 >> $OUT 2>&1
+rm -rf $CONF
+
+# dump and check. if we get this far, we succeeded...
+$FSCK $FSCK_OPT -N test_filesys $TMPFILE >> $OUT 2>&1
+status=$?
+echo Exit status is $status >> $OUT
+
+rm $TMPFILE
+
+#
+# Do the verification
+#
+
+sed -f $cmd_dir/filter.sed -e "s;$TMPFILE;test.img;" -e 's/test_filesys:.*//g' < $OUT > $OUT.new
+mv $OUT.new $OUT
+
+cmp -s $OUT $EXP
+status=$?
+
+if [ "$status" = 0 ] ; then
+	echo "$test_name: $test_description: ok"
+	touch $test_name.ok
+else
+	echo "$test_name: $test_description: failed"
+	diff $DIFF_OPTS $EXP $OUT > $test_name.failed
+fi
+
+unset IMAGE FSCK_OPT OUT EXP CONF
+
+else #if test -x $RESIZE2FS_EXE -a -x $DEBUGFS_EXE; then
+	echo "$test_name: $test_description: skipped"
+fi
+
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