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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: Kees Cook <keescook@chromium.org>
Cc: Anton Altaparmakov <anton@tuxera.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kees Cook 2018-08-17 15:44:14 -07:00 committed by Linus Torvalds
parent 2c27ce9150
commit ab62ef82ea
1 changed files with 10 additions and 2 deletions
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12
fs/ntfs/mft.c
View File

@ -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.