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Commit ab62ef82 authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds
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ntfs: mft: remove VLA usage 

In the quest to remove all stack VLA usage from the kernel[1], this
allocates the maximum size stack buffer.  Existing checks already
require that blocksize >= NTFS_BLOCK_SIZE and mft_record_size <=
PAGE_SIZE, so max_bhs can be at most PAGE_SIZE / NTFS_BLOCK_SIZE.
Sanity checks are added for robustness.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Link: http://lkml.kernel.org/r/20180626172909.41453-4-keescook@chromium.org


Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: Anton Altaparmakov <anton@tuxera.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2c27ce91

fs/ntfs/mft.c

+10 −2
Original line number Diff line number Diff line
@@ -35,6 +35,8 @@ 
#include "mft.h"

#include "ntfs.h"



#define MAX_BHS	(PAGE_SIZE / NTFS_BLOCK_SIZE)



/**

 * map_mft_record_page - map the page in which a specific mft record resides

 * @ni:		ntfs inode whose mft record page to map
@@ -469,7 +471,7 @@ int ntfs_sync_mft_mirror(ntfs_volume *vol, const unsigned long mft_no, 
	struct page *page;

	unsigned int blocksize = vol->sb->s_blocksize;

	int max_bhs = vol->mft_record_size / blocksize;

	struct buffer_head *bhs[max_bhs];

	struct buffer_head *bhs[MAX_BHS];

	struct buffer_head *bh, *head;

	u8 *kmirr;

	runlist_element *rl;
@@ -479,6 +481,8 @@ int ntfs_sync_mft_mirror(ntfs_volume *vol, const unsigned long mft_no, 


	ntfs_debug("Entering for inode 0x%lx.", mft_no);

	BUG_ON(!max_bhs);

	if (WARN_ON(max_bhs > MAX_BHS))

		return -EINVAL;

	if (unlikely(!vol->mftmirr_ino)) {

		/* This could happen during umount... */

		err = ntfs_sync_mft_mirror_umount(vol, mft_no, m);
@@ -674,7 +678,7 @@ int write_mft_record_nolock(ntfs_inode *ni, MFT_RECORD *m, int sync) 
	unsigned int blocksize = vol->sb->s_blocksize;

	unsigned char blocksize_bits = vol->sb->s_blocksize_bits;

	int max_bhs = vol->mft_record_size / blocksize;

	struct buffer_head *bhs[max_bhs];

	struct buffer_head *bhs[MAX_BHS];

	struct buffer_head *bh, *head;

	runlist_element *rl;

	unsigned int block_start, block_end, m_start, m_end;
@@ -684,6 +688,10 @@ int write_mft_record_nolock(ntfs_inode *ni, MFT_RECORD *m, int sync) 
	BUG_ON(NInoAttr(ni));

	BUG_ON(!max_bhs);

	BUG_ON(!PageLocked(page));

	if (WARN_ON(max_bhs > MAX_BHS)) {

		err = -EINVAL;

		goto err_out;

	}

	/*

	 * If the ntfs_inode is clean no need to do anything.  If it is dirty,

	 * mark it as clean now so that it can be redirtied later on if needed.