From 2c98da4e6a3e106c340972adedc6f79c4c1969f2 Mon Sep 17 00:00:00 2001

From: Theodore Ts'o <tytso@mit.edu>

Date: Tue, 28 Dec 2021 12:33:15 -0500

Subject: [PATCH] reisze2fs: sanity check free block group counts when

 calculating minimum size

If one or more block group descriptor's free blocks count is insane,

it's possible this can lead to a infinite loop in the function

calculate_minimum_resize_size(), which is called by resize2fs -P or

resize2fs -M.

Add some sanity checks to avoid this.  In the case where the file

system is corrupt, this will result in resize2fs -P reporting an

incorrect value, but that's OK, since when we try to do an actual

resize operation, resize2fs requires that the file system be freshly

checked using e2fsck.

https://github.com/tytso/e2fsprogs/issues/94

Fixes: ac94445fc01f ("resize2fs: make minimum size estimates more reliable for mounted fs")

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

---

 resize/resize2fs.c        | 13 +++++++++--

 tests/r_corrupt_fs/expect |  4 ++++

 tests/r_corrupt_fs/name   |  1 +

 tests/r_corrupt_fs/script | 45 +++++++++++++++++++++++++++++++++++++++

 4 files changed, 61 insertions(+), 2 deletions(-)

 create mode 100644 tests/r_corrupt_fs/expect

 create mode 100644 tests/r_corrupt_fs/name

 create mode 100644 tests/r_corrupt_fs/script

diff --git a/resize/resize2fs.c b/resize/resize2fs.c

index 8a3d08db..26050fec 100644

--- a/resize/resize2fs.c

+++ b/resize/resize2fs.c

@@ -2928,8 +2928,17 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs, int flags)

 	/* calculate how many blocks are needed for data */

 	data_needed = ext2fs_blocks_count(fs->super);

 	for (grp = 0; grp < fs->group_desc_count; grp++) {

-		data_needed -= calc_group_overhead(fs, grp, old_desc_blocks);

-		data_needed -= ext2fs_bg_free_blocks_count(fs, grp);

+		__u32 n = ext2fs_bg_free_blocks_count(fs, grp);

+

+		if (n > EXT2_BLOCKS_PER_GROUP(fs->super))

+			n = EXT2_BLOCKS_PER_GROUP(fs->super);

+		n += calc_group_overhead(fs, grp, old_desc_blocks);

+		if (data_needed < n) {

+			if (flags & RESIZE_DEBUG_MIN_CALC)

+				printf("file system appears inconsistent?!?\n");

+			return ext2fs_blocks_count(fs->super);

+		}

+		data_needed -= n;

 	}

 #ifdef RESIZE2FS_DEBUG

 	if (flags & RESIZE_DEBUG_MIN_CALC)

diff --git a/tests/r_corrupt_fs/expect b/tests/r_corrupt_fs/expect

new file mode 100644

index 00000000..fe0f2bc4

--- /dev/null

+++ b/tests/r_corrupt_fs/expect

@@ -0,0 +1,4 @@

+mke2fs -q -F -t ext4 -o Linux -b 1024 test.img 32M

+debugfs -w -R "set_bg 1 free_blocks_count 65536" /tmp/foo.img

+resize2fs -P /tmp/foo.img

+Estimated minimum size of the filesystem: 6604

diff --git a/tests/r_corrupt_fs/name b/tests/r_corrupt_fs/name

new file mode 100644

index 00000000..ed627419

--- /dev/null

+++ b/tests/r_corrupt_fs/name

@@ -0,0 +1 @@

+resize2fs -P of a corrupted file system

diff --git a/tests/r_corrupt_fs/script b/tests/r_corrupt_fs/script

new file mode 100644

index 00000000..08af91ed

--- /dev/null

+++ b/tests/r_corrupt_fs/script

@@ -0,0 +1,45 @@

+if ! test -x $RESIZE2FS_EXE -o ! -x $DEBUGFS_EXE; then

+	echo "$test_name: $test_description: skipped (no debugfs/resize2fs)"

+	return 0

+fi

+

+OUT=$test_name.log

+if [ -f $test_dir/expect.gz ]; then

+	EXP=$test_name.tmp

+	gunzip < $test_dir/expect.gz > $EXP1

+else

+	EXP=$test_dir/expect

+fi

+

+echo mke2fs -q -F -t ext4 -o Linux -b 1024 test.img 32M > $OUT.new

+$MKE2FS -q -F -t ext4 -o Linux -b 1024 $TMPFILE 32M >> $OUT.new 2>&1

+

+echo debugfs -w -R \"set_bg 1 free_blocks_count 65536\" /tmp/foo.img >> $OUT.new

+$DEBUGFS -w -R "set_bg 1 free_blocks_count 65536" $TMPFILE > /dev/null 2>&1

+

+if type timeout > /dev/null 2>&1 ; then

+   TIMEOUT="timeout -v 30s"

+else

+   TIMEOUT=

+fi

+

+echo resize2fs -P /tmp/foo.img >> $OUT.new

+$TIMEOUT $RESIZE2FS -P $TMPFILE  >> $OUT.new 2>&1

+

+sed -f $cmd_dir/filter.sed < $OUT.new > $OUT

+

+rm -f $TMPFILE $OUT.new

+

+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

+	rm -f $test_name.tmp

+fi

+

+unset IMAGE OUT EXP TIMEOUT

-- 

2.34.1