On Sun, Jul 15, 2018 at 08:56:57PM -0700, Kees Cook wrote: > In the quest to remove all stack VLA usage from the kernel[1], this > removes the discouraged use of AHASH_REQUEST_ON_STACK by switching to > shash directly and allocating the descriptor in heap memory (which should > be fine: the tfm has already been allocated there too). > > [1] > https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qpxydaacu1rq...@mail.gmail.com > > Signed-off-by: Kees Cook <keesc...@chromium.org> > --- > arch/x86/power/hibernate_64.c | 35 +++++++++++++++++++---------------- > 1 file changed, 19 insertions(+), 16 deletions(-) > > diff --git a/arch/x86/power/hibernate_64.c b/arch/x86/power/hibernate_64.c > index 67ccf64c8bd8..0ed01bb935a6 100644 > --- a/arch/x86/power/hibernate_64.c > +++ b/arch/x86/power/hibernate_64.c > @@ -233,28 +233,31 @@ struct restore_data_record { > */ > static int get_e820_md5(struct e820_table *table, void *buf) > { > - struct scatterlist sg; > - struct crypto_ahash *tfm; > + struct crypto_shash *tfm; > + struct shash_desc *desc; > int size; > int ret = 0; > > - tfm = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC); > + tfm = crypto_alloc_shash("md5", 0, 0); > if (IS_ERR(tfm)) > return -ENOMEM; > > - { > - AHASH_REQUEST_ON_STACK(req, tfm); > - size = offsetof(struct e820_table, entries) + sizeof(struct > e820_entry) * table->nr_entries; > - ahash_request_set_tfm(req, tfm); > - sg_init_one(&sg, (u8 *)table, size); > - ahash_request_set_callback(req, 0, NULL, NULL); > - ahash_request_set_crypt(req, &sg, buf, size); > - > - if (crypto_ahash_digest(req)) > - ret = -EINVAL; > - ahash_request_zero(req); > - } > - crypto_free_ahash(tfm); > + desc = kmalloc(sizeof(struct shash_desc) + crypto_shash_descsize(tfm), > + GFP_KERNEL); > + if (!desc) > + return -ENOMEM;
Need crypto_free_shash(tfm) if the kmalloc() here fails. > + > + desc->tfm = tfm; > + desc->flags = 0; > + > + size = offsetof(struct e820_table, entries) + > + sizeof(struct e820_entry) * table->nr_entries; > + > + if (crypto_shash_digest(desc, (u8 *)table, size, buf)) > + ret = -EINVAL; > + > + kzfree(desc); > + crypto_free_shash(tfm); > > return ret; > } > -- > 2.17.1 > > > -- > Kees Cook > Pixel Security
