1. 01 Mar, 2024 3 commits
    • Varshini Rajendran's avatar
      7bb9f42d
    • Eric Biggers's avatar
      crypto: remove CONFIG_CRYPTO_STATS · 2beb81fb
      Eric Biggers authored
      Remove support for the "Crypto usage statistics" feature
      (CONFIG_CRYPTO_STATS).  This feature does not appear to have ever been
      used, and it is harmful because it significantly reduces performance and
      is a large maintenance burden.
      
      Covering each of these points in detail:
      
      1. Feature is not being used
      
      Since these generic crypto statistics are only readable using netlink,
      it's fairly straightforward to look for programs that use them.  I'm
      unable to find any evidence that any such programs exist.  For example,
      Debian Code Search returns no hits except the kernel header and kernel
      code itself and translations of the kernel header:
      https://codesearch.debian.net/search?q=CRYPTOCFGA_STAT&literal=1&perpkg=1
      
      The patch series that added this feature in 2018
      (https://lore.kernel.org/linux-crypto/1537351855-16618-1-git-send-email-clabbe@baylibre.com/)
      said "The goal is to have an ifconfig for crypto device."  This doesn't
      appear to have happened.
      
      It's not clear that there is real demand for crypto statistics.  Just
      because the kernel provides other types of statistics such as I/O and
      networking statistics and some people find those useful does not mean
      that crypto statistics are useful too.
      
      Further evidence that programs are not using CONFIG_CRYPTO_STATS is that
      it was able to be disabled in RHEL and Fedora as a bug fix
      (https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/2947).
      
      Even further evidence comes from the fact that there are and have been
      bugs in how the stats work, but they were never reported.  For example,
      before Linux v6.7 hash stats were double-counted in most cases.
      
      There has also never been any documentation for this feature, so it
      might be hard to use even if someone wanted to.
      
      2. CONFIG_CRYPTO_STATS significantly reduces performance
      
      Enabling CONFIG_CRYPTO_STATS significantly reduces the performance of
      the crypto API, even if no program ever retrieves the statistics.  This
      primarily affects systems with large number of CPUs.  For example,
      https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039576 reported
      that Lustre client encryption performance improved from 21.7GB/s to
      48.2GB/s by disabling CONFIG_CRYPTO_STATS.
      
      It can be argued that this means that CONFIG_CRYPTO_STATS should be
      optimized with per-cpu counters similar to many of the networking
      counters.  But no one has done this in 5+ years.  This is consistent
      with the fact that the feature appears to be unused, so there seems to
      be little interest in improving it as opposed to just disabling it.
      
      It can be argued that because CONFIG_CRYPTO_STATS is off by default,
      performance doesn't matter.  But Linux distros tend to error on the side
      of enabling options.  The option is enabled in Ubuntu and Arch Linux,
      and until recently was enabled in RHEL and Fedora (see above).  So, even
      just having the option available is harmful to users.
      
      3. CONFIG_CRYPTO_STATS is a large maintenance burden
      
      There are over 1000 lines of code associated with CONFIG_CRYPTO_STATS,
      spread among 32 files.  It significantly complicates much of the
      implementation of the crypto API.  After the initial submission, many
      fixes and refactorings have consumed effort of multiple people to keep
      this feature "working".  We should be spending this effort elsewhere.
      
      Cc: Corentin Labbe <clabbe@baylibre.com>
      Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
      Acked-by: default avatarArd Biesheuvel <ardb@kernel.org>
      Acked-by: default avatarCorentin Labbe <clabbe@baylibre.com>
      Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      2beb81fb
    • Herbert Xu's avatar
      crypto: dh - Make public key test FIPS-only · f66a211e
      Herbert Xu authored
      The function dh_is_pubkey_valid was added to for FIPS but it was
      only partially conditional to fips_enabled.
      
      In particular, the first test in the function relies on the last
      test to work properly, but the last test is only run in FIPS mode.
      
      Fix this inconsistency by making the whole function conditional
      on fips_enabled.
      Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      f66a211e
  2. 24 Feb, 2024 16 commits
  3. 17 Feb, 2024 7 commits
  4. 09 Feb, 2024 12 commits
  5. 02 Feb, 2024 2 commits