linux-ext4 - [PATCH 1/6] libext2fs: ext2fs_dup_handle should not alias MMP buffers

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Message-ID: <20130829004350.3190.12494.stgit@blackbox.djwong.org>
Date:	Wed, 28 Aug 2013 17:43:51 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	tytso@....edu, darrick.wong@...cle.com
Cc:	linux-ext4@...r.kernel.org
Subject: [PATCH 1/6] libext2fs: ext2fs_dup_handle should not alias MMP buffers

It turns out that resize2fs uses ext2fs_dup_handle to duplicate fs handles.  If
MMP is enabled, this causes both handles to share MMP buffers, which is bad
news when it comes time to free both handles.  Change the code to (we hope) fix
this.  This prevents resize2fs from failing with a double-free error when
handed a MMP filesystem.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 lib/ext2fs/dupfs.c |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/lib/ext2fs/dupfs.c b/lib/ext2fs/dupfs.c
index 64d3124..02721e1 100644
--- a/lib/ext2fs/dupfs.c
+++ b/lib/ext2fs/dupfs.c
@@ -40,6 +40,9 @@ errcode_t ext2fs_dup_handle(ext2_filsys src, ext2_filsys *dest)
 	fs->block_map = 0;
 	fs->badblocks = 0;
 	fs->dblist = 0;
+	fs->mmp_buf = 0;
+	fs->mmp_cmp = 0;
+	fs->mmp_fd = -1;

 	io_channel_bumpcount(fs->io);
 	if (fs->icache)
@@ -87,6 +90,28 @@ errcode_t ext2fs_dup_handle(ext2_filsys src, ext2_filsys *dest)
 		if (retval)
 			goto errout;
 	}
+	if (src->mmp_buf) {
+		retval = ext2fs_get_mem(src->blocksize, &fs->mmp_buf);
+		if (retval)
+			goto errout;
+		memcpy(fs->mmp_buf, src->mmp_buf, src->blocksize);
+	}
+	if (src->mmp_fd >= 0) {
+		fs->mmp_fd = dup(src->mmp_fd);
+		if (fs->mmp_fd < 0) {
+			retval = EXT2_ET_MMP_OPEN_DIRECT;
+			goto errout;
+		}
+	}
+	if (src->mmp_cmp) {
+		int align = ext2fs_get_dio_alignment(src->mmp_fd);
+
+		retval = ext2fs_get_memalign(src->blocksize, align,
+					     &fs->mmp_cmp);
+		if (retval)
+			goto errout;
+		memcpy(fs->mmp_cmp, src->mmp_cmp, src->blocksize);
+	}
 	*dest = fs;
 	return 0;
 errout:

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