| Message ID | 20180716035657.GA32180@beast (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
On Sun 2018-07-15 20:56:57, 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=qPXydAacU1RqZWA@mail.gmail.com > > Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Pavel Machek <pavel@ucw.cz> , provided it was tested. Pavel
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=qPXydAacU1RqZWA@mail.gmail.com > > Signed-off-by: Kees Cook <keescook@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
On Mon, Jul 16, 2018 at 10:22 AM, Eric Biggers <ebiggers@google.com> wrote: > 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=qPXydAacU1RqZWA@mail.gmail.com >> >> Signed-off-by: Kees Cook <keescook@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. Ah thanks! Fixed now for the next version. -Kees
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; + + 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; }
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=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/x86/power/hibernate_64.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-)