From: Kees Cook <keescook@xxxxxxxxxxxx> Subject: ntfs: aops: remove VLA usage In the quest to remove all stack VLA usage from the kernel[1], this uses the maximum size needed on the stack and adds a sanity check for robustness: index.block_size cannot be larger than PAGE_SIZE nor less than NTFS_BLOCK_SIZE. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/20180626172909.41453-2-keescook@xxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Anton Altaparmakov <anton@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/ntfs/aops.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/ntfs/aops.c~ntfs-aops-remove-vla-usage +++ a/fs/ntfs/aops.c @@ -922,7 +922,7 @@ static int ntfs_write_mst_block(struct p ntfs_volume *vol = ni->vol; u8 *kaddr; unsigned int rec_size = ni->itype.index.block_size; - ntfs_inode *locked_nis[PAGE_SIZE / rec_size]; + ntfs_inode *locked_nis[PAGE_SIZE / NTFS_BLOCK_SIZE]; struct buffer_head *bh, *head, *tbh, *rec_start_bh; struct buffer_head *bhs[MAX_BUF_PER_PAGE]; runlist_element *rl; @@ -931,6 +931,9 @@ static int ntfs_write_mst_block(struct p bool sync, is_mft, page_is_dirty, rec_is_dirty; unsigned char bh_size_bits; + if (WARN_ON(rec_size < NTFS_BLOCK_SIZE)) + return -EINVAL; + ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, page index " "0x%lx.", vi->i_ino, ni->type, page->index); BUG_ON(!NInoNonResident(ni)); _
