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From: Kees C. <kee...@ch...> - 2018-06-26 17:57:26
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In the quest to remove all stack VLA usage from the kernel[1], this moves the stack buffer used during decompression to be allocated externally. The existing "dest_max_index" used in the VLA is bounded by cb_max_page. cb_max_page is bounded by max_page, and max_page is bounded by nr_pages. Since nr_pages is used for the "pages" allocation, it can similarly be used for the "completed_pages" allocation and passed into the decompression function. The error paths are updated to free the new allocation. [1] https://lkml.kernel.org/r/CA+...@ma... Cc: Anton Altaparmakov <an...@tu...> Cc: lin...@li... Signed-off-by: Kees Cook <kee...@ch...> --- fs/ntfs/compress.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/fs/ntfs/compress.c b/fs/ntfs/compress.c index fbd0090d7d0c..df7c32b5fac7 100644 --- a/fs/ntfs/compress.c +++ b/fs/ntfs/compress.c @@ -128,6 +128,7 @@ static inline void handle_bounds_compressed_page(struct page *page, /** * ntfs_decompress - decompress a compression block into an array of pages * @dest_pages: destination array of pages + * @completed_pages: scratch space to track completed pages * @dest_index: current index into @dest_pages (IN/OUT) * @dest_ofs: current offset within @dest_pages[@dest_index] (IN/OUT) * @dest_max_index: maximum index into @dest_pages (IN) @@ -162,10 +163,10 @@ static inline void handle_bounds_compressed_page(struct page *page, * Note to hackers: This function may not sleep until it has finished accessing * the compression block @cb_start as it is a per-CPU buffer. */ -static int ntfs_decompress(struct page *dest_pages[], int *dest_index, - int *dest_ofs, const int dest_max_index, const int dest_max_ofs, - const int xpage, char *xpage_done, u8 *const cb_start, - const u32 cb_size, const loff_t i_size, +static int ntfs_decompress(struct page *dest_pages[], int completed_pages[], + int *dest_index, int *dest_ofs, const int dest_max_index, + const int dest_max_ofs, const int xpage, char *xpage_done, + u8 *const cb_start, const u32 cb_size, const loff_t i_size, const s64 initialized_size) { /* @@ -190,9 +191,6 @@ static int ntfs_decompress(struct page *dest_pages[], int *dest_index, /* Variables for tag and token parsing. */ u8 tag; /* Current tag. */ int token; /* Loop counter for the eight tokens in tag. */ - - /* Need this because we can't sleep, so need two stages. */ - int completed_pages[dest_max_index - *dest_index + 1]; int nr_completed_pages = 0; /* Default error code. */ @@ -516,6 +514,7 @@ int ntfs_read_compressed_block(struct page *page) unsigned int cb_clusters, cb_max_ofs; int block, max_block, cb_max_page, bhs_size, nr_bhs, err = 0; struct page **pages; + int *completed_pages; unsigned char xpage_done = 0; ntfs_debug("Entering, page->index = 0x%lx, cb_size = 0x%x, nr_pages = " @@ -528,14 +527,16 @@ int ntfs_read_compressed_block(struct page *page) BUG_ON(ni->name_len); pages = kmalloc_array(nr_pages, sizeof(struct page *), GFP_NOFS); + completed_pages = kmalloc_array(nr_pages + 1, sizeof(int), GFP_NOFS); /* Allocate memory to store the buffer heads we need. */ bhs_size = cb_size / block_size * sizeof(struct buffer_head *); bhs = kmalloc(bhs_size, GFP_NOFS); - if (unlikely(!pages || !bhs)) { + if (unlikely(!pages || !bhs || !completed_pages)) { kfree(bhs); kfree(pages); + kfree(completed_pages); unlock_page(page); ntfs_error(vol->sb, "Failed to allocate internal buffers."); return -ENOMEM; @@ -562,6 +563,7 @@ int ntfs_read_compressed_block(struct page *page) if (xpage >= max_page) { kfree(bhs); kfree(pages); + kfree(completed_pages); zero_user(page, 0, PAGE_SIZE); ntfs_debug("Compressed read outside i_size - truncated?"); SetPageUptodate(page); @@ -854,10 +856,10 @@ int ntfs_read_compressed_block(struct page *page) unsigned int prev_cur_page = cur_page; ntfs_debug("Found compressed compression block."); - err = ntfs_decompress(pages, &cur_page, &cur_ofs, - cb_max_page, cb_max_ofs, xpage, &xpage_done, - cb_pos, cb_size - (cb_pos - cb), i_size, - initialized_size); + err = ntfs_decompress(pages, completed_pages, &cur_page, + &cur_ofs, cb_max_page, cb_max_ofs, xpage, + &xpage_done, cb_pos, cb_size - (cb_pos - cb), + i_size, initialized_size); /* * We can sleep from now on, lock already dropped by * ntfs_decompress(). @@ -912,6 +914,7 @@ int ntfs_read_compressed_block(struct page *page) /* We no longer need the list of pages. */ kfree(pages); + kfree(completed_pages); /* If we have completed the requested page, we return success. */ if (likely(xpage_done)) @@ -956,5 +959,6 @@ int ntfs_read_compressed_block(struct page *page) } } kfree(pages); + kfree(completed_pages); return -EIO; } -- 2.17.1 |
