The patch titled
Subject: ntfs: mft: remove VLA usage
has been added to the -mm tree. Its filename is
ntfs-mft-remove-vla-usage.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ntfs-mft-remove-vla-usage.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ntfs-mft-remove-vla-usage.patch
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The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Kees Cook <keescook@xxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20180626172909.41453-4-keescook@xxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Anton Altaparmakov <anton@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN fs/ntfs/mft.c~ntfs-mft-remove-vla-usage fs/ntfs/mft.c
--- a/fs/ntfs/mft.c~ntfs-mft-remove-vla-usage
+++ a/fs/ntfs/mft.c
@@ -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 *vo
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 *vo
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 *
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 *
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.
_
Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are
ntfs-aops-remove-vla-usage.patch
ntfs-decompress-remove-vla-usage.patch
ntfs-mft-remove-vla-usage.patch
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