Re: [PATCH 1/1] use crc32 instead of md5 for hibernation e820 integrity check

Rafael J. Wysocki
2021-04-01T18:45:13Z

On Thu, Apr 1, 2021 at 3:34 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Thu, Apr 1, 2021 at 2:25 PM Chris von Recklinghausen
> <crecklin@redhat.com> wrote:
> >
> > Suspend fails on a system in fips mode because md5 is used for the e820
> > integrity check and is not available. Use crc32 instead.
> >
> > Fixes: 62a03defeabd ("PM / hibernate: Verify the consistent of e820 memory map
> > by md5 digest")
> > Signed-off-by: Chris von Recklinghausen <crecklin@redhat.com>
> > ---
> > arch/x86/power/hibernate.c | 31 +++++++++++++++++--------------
> > 1 file changed, 17 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/x86/power/hibernate.c b/arch/x86/power/hibernate.c
> > index cd3914fc9f3d..6a3f4e32e49c 100644
> > --- a/arch/x86/power/hibernate.c
> > +++ b/arch/x86/power/hibernate.c
> > @@ -55,31 +55,31 @@ int pfn_is_nosave(unsigned long pfn)
> > }
> >
> >
> > -#define MD5_DIGEST_SIZE 16
> > +#define CRC32_DIGEST_SIZE 16
> >
> > struct restore_data_record {
> > unsigned long jump_address;
> > unsigned long jump_address_phys;
> > unsigned long cr3;
> > unsigned long magic;
> > - u8 e820_digest[MD5_DIGEST_SIZE];
> > + u8 e820_digest[CRC32_DIGEST_SIZE];
> > };
>
> No.
>
> CRC32 was used here before and it was deemed insufficient.
>
> Please find a different way to address this issue.

Well, I guess I'm going to change my mind on this, so we can go with
this patch, but please bump up RESTORE_MAGIC too.

> > -#if IS_BUILTIN(CONFIG_CRYPTO_MD5)
> > +#if IS_BUILTIN(CONFIG_CRYPTO_CRC32)
> > /**
> > - * get_e820_md5 - calculate md5 according to given e820 table
> > + * get_e820_crc32 - calculate crc32 according to given e820 table
> > *
> > * @table: the e820 table to be calculated
> > - * @buf: the md5 result to be stored to
> > + * @buf: the crc32 result to be stored to
> > */
> > -static int get_e820_md5(struct e820_table *table, void *buf)
> > +static int get_e820_crc32(struct e820_table *table, void *buf)
> > {
> > struct crypto_shash *tfm;
> > struct shash_desc *desc;
> > int size;
> > int ret = 0;
> >
> > - tfm = crypto_alloc_shash("md5", 0, 0);
> > + tfm = crypto_alloc_shash("crc32", 0, 0);
> > if (IS_ERR(tfm))
> > return -ENOMEM;
> >
> > @@ -107,24 +107,24 @@ static int get_e820_md5(struct e820_table *table, void *buf)
> >
> > static int hibernation_e820_save(void *buf)
> > {
> > - return get_e820_md5(e820_table_firmware, buf);
> > + return get_e820_crc32(e820_table_firmware, buf);
> > }
> >
> > static bool hibernation_e820_mismatch(void *buf)
> > {
> > int ret;
> > - u8 result[MD5_DIGEST_SIZE];
> > + u8 result[CRC32_DIGEST_SIZE];
> >
> > - memset(result, 0, MD5_DIGEST_SIZE);
> > + memset(result, 0, CRC32_DIGEST_SIZE);
> > /* If there is no digest in suspend kernel, let it go. */
> > - if (!memcmp(result, buf, MD5_DIGEST_SIZE))
> > + if (!memcmp(result, buf, CRC32_DIGEST_SIZE))
> > return false;
> >
> > - ret = get_e820_md5(e820_table_firmware, result);
> > + ret = get_e820_crc32(e820_table_firmware, result);
> > if (ret)
> > return true;
> >
> > - return memcmp(result, buf, MD5_DIGEST_SIZE) ? true : false;
> > + return memcmp(result, buf, CRC32_DIGEST_SIZE) ? true : false;
> > }
> > #else
> > static int hibernation_e820_save(void *buf)
> > @@ -134,7 +134,7 @@ static int hibernation_e820_save(void *buf)
> >
> > static bool hibernation_e820_mismatch(void *buf)
> > {
> > - /* If md5 is not builtin for restore kernel, let it go. */
> > + /* If crc32 is not builtin for restore kernel, let it go. */
> > return false;
> > }
> > #endif
> > @@ -160,6 +160,9 @@ int arch_hibernation_header_save(void *addr, unsigned int max_size)
> > rdr->jump_address = (unsigned long)restore_registers;
> > rdr->jump_address_phys = __pa_symbol(restore_registers);
> >
> > + /* crc32 digest size is 4 but digest buffer size is 16 so zero it all */
> > + memset(rdr->e820_digest, 0, CRC32_DIGEST_SIZE);
> > +
> > /*
> > * The restore code fixes up CR3 and CR4 in the following sequence:
> > *
> > --
> > 2.18.1
> >