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]; ? -Kees -- Kees Cook Pixel Security
