On Wed, May 30, 2018 at 2:33 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > On Tue, May 29, 2018 at 3:40 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: >> [ add Vinod's korg address ] >> >> On Tue, May 29, 2018 at 3:37 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: >>> [ adding linux-raid ] >>> >>> Apologies for the delay, the recent ping from Kees made me take a closer look. >>> >>> On Sat, May 5, 2018 at 12:58 AM, Kyle Spiers <ksspiers@xxxxxxxxxx> wrote: >>>> In the quest to remove VLAs from the kernel[1], this moves the >>>> allocation of coefs and blocks from the stack to being kmalloc()ed. >>>> >>>> [1] https://lkml.org/lkml/2018/3/7/621 >>>> >>>> Signed-off-by: Kyle Spiers <ksspiers@xxxxxxxxxx> >>>> --- >>>> Forgot to add slab.h >>>> --- >>>> crypto/async_tx/async_pq.c | 18 ++++++++++++++---- >>>> crypto/async_tx/raid6test.c | 9 ++++++++- >>>> 2 files changed, 22 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c >>>> index 56bd612927ab..af1912313a23 100644 >>>> --- a/crypto/async_tx/async_pq.c >>>> +++ b/crypto/async_tx/async_pq.c >>>> @@ -194,9 +194,9 @@ async_gen_syndrome(struct page **blocks, unsigned int offset, int disks, >>>> (src_cnt <= dma_maxpq(device, 0) || >>>> dma_maxpq(device, DMA_PREP_CONTINUE) > 0) && >>>> is_dma_pq_aligned(device, offset, 0, len)) { >>>> - struct dma_async_tx_descriptor *tx; >>>> + struct dma_async_tx_descriptor *tx = NULL; >>>> enum dma_ctrl_flags dma_flags = 0; >>>> - unsigned char coefs[src_cnt]; >>>> + unsigned char *coefs; >>> At a minimum this needs to be GFP_NOIO since raid may be in the >>> page-reclaim path. >>> >>> However, I think it may be better to allocate this with the rest of >>> the stripe resources and pass it in as a scratch buffer. See the usage >>> / implementation of scribble_alloc() in drivers/md/raid5.c. > > Given this: > > int src_cnt = disks - 2; > ... > BUG_ON(disks > 255 || ...) > > what about just making something like: > > #define MAX_DISKS 255 > ... > int src_cnt = disks - 2; > ... > BUG_ON(disks > MAX_DISKS || ...) > ... > unsigned char coefs[MAX_DISKS]; > > ? Yeah, we were already potentially suffering a value that large on the stack in a max config case anyway with the VLA. Looks ok to me.
