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Commit af5eb745 authored by Anton Altaparmakov's avatar Anton Altaparmakov Committed by Linus Torvalds
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NTFS: Fix invalid pointer dereference in ntfs_mft_record_alloc(). 



In ntfs_mft_record_alloc() when mapping the new extent mft record with
map_extent_mft_record() we overwrite @m with the return value and on
error, we then try to use the old @m but that is no longer there as @m
now contains an error code instead so we crash when dereferencing the
error code as if it were a pointer.

The simple fix is to use a temporary variable to store the return value
thus preserving the original @m for later use.  This is a backport from
the commercial Tuxera-NTFS driver and is well tested...

Thanks go to Julia Lawall for pointing this out (whilst I had fixed it
in the commercial driver I had failed to fix it in the Linux kernel).

Signed-off-by: default avatarAnton Altaparmakov <anton@tuxera.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9fbf0c08

Documentation/filesystems/ntfs.txt

+2 −0
Original line number Diff line number Diff line
@@ -460,6 +460,8 @@ Note, a technical ChangeLog aimed at kernel hackers is in fs/ntfs/ChangeLog. 
2.1.30:

	- Fix writev() (it kept writing the first segment over and over again

	  instead of moving onto subsequent segments).

	- Fix crash in ntfs_mft_record_alloc() when mapping the new extent mft

	  record failed.

2.1.29:

	- Fix a deadlock when mounting read-write.

2.1.28:

fs/ntfs/mft.c

+7 −4
Original line number Diff line number Diff line 
/**

 * mft.c - NTFS kernel mft record operations. Part of the Linux-NTFS project.

 *

 * Copyright (c) 2001-2006 Anton Altaparmakov

 * Copyright (c) 2001-2011 Anton Altaparmakov and Tuxera Inc.

 * Copyright (c) 2002 Richard Russon

 *

 * This program/include file is free software; you can redistribute it and/or
@@ -2576,6 +2576,8 @@ ntfs_inode *ntfs_mft_record_alloc(ntfs_volume *vol, const int mode, 
	flush_dcache_page(page);

	SetPageUptodate(page);

	if (base_ni) {

		MFT_RECORD *m_tmp;



		/*

		 * Setup the base mft record in the extent mft record.  This

		 * completes initialization of the allocated extent mft record
@@ -2588,11 +2590,11 @@ ntfs_inode *ntfs_mft_record_alloc(ntfs_volume *vol, const int mode, 
		 * attach it to the base inode @base_ni and map, pin, and lock

		 * its, i.e. the allocated, mft record.

		 */

		m = map_extent_mft_record(base_ni, bit, &ni);

		if (IS_ERR(m)) {

		m_tmp = map_extent_mft_record(base_ni, bit, &ni);

		if (IS_ERR(m_tmp)) {

			ntfs_error(vol->sb, "Failed to map allocated extent "

					"mft record 0x%llx.", (long long)bit);

			err = PTR_ERR(m);

			err = PTR_ERR(m_tmp);

			/* Set the mft record itself not in use. */

			m->flags &= cpu_to_le16(

					~le16_to_cpu(MFT_RECORD_IN_USE));
@@ -2603,6 +2605,7 @@ ntfs_inode *ntfs_mft_record_alloc(ntfs_volume *vol, const int mode, 
			ntfs_unmap_page(page);

			goto undo_mftbmp_alloc;

		}

		BUG_ON(m != m_tmp);

		/*

		 * Make sure the allocated mft record is written out to disk.

		 * No need to set the inode dirty because the caller is going