On Thu, Jul 5, 2018 at 1:44 PM, Arnd Bergmann <a...@arndb.de> wrote: > On Tue, Jun 26, 2018 at 7:29 PM, Kees Cook <keesc...@chromium.org> wrote: >> 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=qpxydaacu1rq...@mail.gmail.com >> >> Cc: Anton Altaparmakov <an...@tuxera.com> >> Cc: linux-ntfs-...@lists.sourceforge.net >> Signed-off-by: Kees Cook <keesc...@chromium.org> >> --- >> fs/ntfs/aops.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c >> index 3a2e509c77c5..58dadff3e0e0 100644 >> --- a/fs/ntfs/aops.c >> +++ b/fs/ntfs/aops.c >> @@ -926,7 +926,7 @@ static int ntfs_write_mst_block(struct page *page, >> 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; > > This has uncovered what looks like a preexisting bug on architectures > with large page size, this is what I get with 64K pages on arm64: > > fs/ntfs/aops.c: In function 'ntfs_write_mst_block': > fs/ntfs/aops.c:1328:1: error: the frame size of 2432 bytes is larger > than 2048 bytes [-Werror=frame-larger-than=] > > Since both ntfs and 64k pages are fairly obscure features, we might > get away with just disabling the combination of the two in Kconfig. > > Using dynamic allocation might be tricky here, since I assume this > could be called during writeback in order to free memory, and I can't > immediately see any better fix.
I'm open to whatever. In crypto, my series uses specifically 4096 for PAGE_SIZE instead of using PAGE_SIZE, since it wasn't really related. Here, though, I can't tell if it really IS a page size issue. -Kees -- Kees Cook Pixel Security
