From: "Dilger, Andreas" <andreas.dilger@intel.com>
Subject: Re: [PATCH] e2image: double free when restoring image
Date: Fri, 29 Nov 2013 17:45:21 +0000
Message-ID: <2536F444-3B5C-4A73-94A1-9464F89B29CD@intel.com>
References: <529664F6.3040103@ddn.com>
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Cc: "tytso@mit.edu" <tytso@mit.edu>,
	"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>
To: Kit Westneat <kwestneat@ddn.com>
In-Reply-To: <529664F6.3040103@ddn.com>
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Sender: linux-ext4-owner@vger.kernel.org

Kit, thanks for sending the patch to the list. 

You'll need to add a Signed-off-by: line. You can also add Reviewed-by: from me as well. 

Cheers, Andreas

On 2013-11-27, at 14:33, "Kit Westneat" <kwestneat@ddn.com> wrote:

> Hello,
> 
> I've been running into a double free when trying to apply an e2image to a
> loopback device:
> 
> # e2image /dev/sda1 sda1.img
> e2image 1.43-WIP (8-Jul-2013)
> # dd if=/dev/zero of=./lofile bs=1M seek=1k count=1
> 1+0 records in
> 1+0 records out
> 1048576 bytes (1.0 MB) copied, 0.00131481 s, 798 MB/s
> # losetup /dev/loop0 ./lofile
> # e2image -I /dev/loop0 ./sda1.img
> e2image 1.43-WIP (8-Jul-2013)
> *** glibc detected *** e2image: double free or corruption (!prev): 0x00000000011c3fd0 ***
> ======= Backtrace: =========
> /lib64/libc.so.6(+0x75296)[0x7f107bf62296]
> e2image[0x4125ab]
> e2image[0x408674]
> e2image[0x40448c]
> /lib64/libc.so.6(__libc_start_main+0xfd)[0x7f107bf0bcdd]
> e2image[0x401ce9]
> ======= Memory map: ========
> 00400000-00425000 r-xp 00000000 fd:00 8907                               /sbin/e2image
> 00625000-00626000 rw-p 00025000 fd:00 8907                               /sbin/e2image
> 011b1000-011f3000 rw-p 00000000 00:00 0                                  [heap]
> 7f1075e46000-7f1075e5c000 r-xp 00000000 fd:00 50                         /lib64/libgcc_s-4.4.6-20110824.so.1
> 7f1075e5c000-7f107605b000 ---p 00016000 fd:00 50                         /lib64/libgcc_s-4.4.6-20110824.so.1
> 7f107605b000-7f107605c000 rw-p 00015000 fd:00 50                         /lib64/libgcc_s-4.4.6-20110824.so.1
> 7f107605c000-7f107beed000 r--p 00000000 fd:00 3172                       /usr/lib/locale/locale-archive
> 7f107beed000-7f107c073000 r-xp 00000000 fd:00 3189                       /lib64/libc-2.12.so
> 7f107c073000-7f107c273000 ---p 00186000 fd:00 3189                       /lib64/libc-2.12.so
> 7f107c273000-7f107c277000 r--p 00186000 fd:00 3189                       /lib64/libc-2.12.so
> 7f107c277000-7f107c278000 rw-p 0018a000 fd:00 3189                       /lib64/libc-2.12.so
> 7f107c278000-7f107c27d000 rw-p 00000000 00:00 0
> 7f107c27d000-7f107c294000 r-xp 00000000 fd:00 3213                       /lib64/libpthread-2.12.so
> 7f107c294000-7f107c493000 ---p 00017000 fd:00 3213                       /lib64/libpthread-2.12.so
> 7f107c493000-7f107c494000 r--p 00016000 fd:00 3213                       /lib64/libpthread-2.12.so
> 7f107c494000-7f107c495000 rw-p 00017000 fd:00 3213                       /lib64/libpthread-2.12.so
> 7f107c495000-7f107c499000 rw-p 00000000 00:00 0
> 7f107c499000-7f107c4b9000 r-xp 00000000 fd:00 3182                       /lib64/ld-2.12.so
> 7f107c6ad000-7f107c6b0000 rw-p 00000000 00:00 0
> 7f107c6b6000-7f107c6b8000 rw-p 00000000 00:00 0
> 7f107c6b8000-7f107c6b9000 r--p 0001f000 fd:00 3182                       /lib64/ld-2.12.so
> 7f107c6b9000-7f107c6ba000 rw-p 00020000 fd:00 3182                       /lib64/ld-2.12.so
> 7f107c6ba000-7f107c6bb000 rw-p 00000000 00:00 0
> 7fffa93b9000-7fffa93ce000 rw-p 00000000 00:00 0                          [stack]
> 7fffa93ff000-7fffa9400000 r-xp 00000000 00:00 0                          [vdso]
> ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
> Aborted
> 
> It appears to be due to a mismatch between the IO channel block size and the FS
> block size. ext2fs_rewrite_to_io is resetting the fs->io to be the IO channel of
> the new device, but that device still has the default unix IO channel block size
> of 1k. I have included a patch to copy the old IO block size into the new IO
> blocksize, which seems to solve the double free.
> 
> Thanks,
> Kit
> 
> diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
> index 2ad9114..69660ff 100644
> --- a/lib/ext2fs/openfs.c
> +++ b/lib/ext2fs/openfs.c
> @@ -479,6 +479,7 @@ errcode_t ext2fs_rewrite_to_io(ext2_filsys fs, io_channel new_io)
> {
>     if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
>         return EXT2_ET_NOT_IMAGE_FILE;
> +    new_io->block_size = fs->io->block_size;
>     fs->io = fs->image_io = new_io;
>     fs->flags |= EXT2_FLAG_DIRTY | EXT2_FLAG_RW |
>         EXT2_FLAG_BB_DIRTY | EXT2_FLAG_IB_DIRTY;
>