linux.git/include/crypto/algapi.h, branch v6.12.80

crypto: remove CONFIG_CRYPTO_STATS

2024-04-02T02:49:38+00:00

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 a 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.

Acked-by: Ard Biesheuvel
Acked-by: Corentin Labbe
Signed-off-by: Eric Biggers
Signed-off-by: Herbert Xu

crypto: shash - remove crypto_shash_ctx_aligned()

2023-10-27T10:04:28+00:00

crypto_shash_ctx_aligned() is no longer used, and it is useless now that
shash algorithms don't support nonzero alignmasks, so remove it.

Also remove crypto_tfm_ctx_aligned() which was only called by
crypto_shash_ctx_aligned().  It's unlikely to be useful again, since it
seems inappropriate to use cra_alignmask to represent alignment for the
tfm context when it already means alignment for inputs/outputs.

Signed-off-by: Eric Biggers 
Signed-off-by: Herbert Xu

crypto: api - Use work queue in crypto_destroy_instance

2023-08-11T11:19:27+00:00

The function crypto_drop_spawn expects to be called in process
context.  However, when an instance is unregistered while it still
has active users, the last user may cause the instance to be freed
in atomic context.

Fix this by delaying the freeing to a work queue.

Fixes: 6bfd48096ff8 ("[CRYPTO] api: Added spawns")
Reported-by: Florent Revest 
Reported-by: syzbot+d769eed29cc42d75e2a3@syzkaller.appspotmail.com
Reported-by: syzbot+610ec0671f51e838436e@syzkaller.appspotmail.com
Signed-off-by: Herbert Xu 
Tested-by: Florent Revest 
Acked-by: Florent Revest 
Signed-off-by: Herbert Xu

crypto: api - Remove crypto_init_ops()

2023-06-23T08:15:36+00:00

Purge crypto_type::init() as well.
The last user seems to be gone with commit d63007eb954e ("crypto:
ablkcipher - remove deprecated and unused ablkcipher support").

Signed-off-by: Dmitry Safonov 
Reviewed-by: Eric Biggers 
Signed-off-by: Herbert Xu

crypto: api - Move low-level functions into algapi.h

2023-04-14T10:59:34+00:00

A number of low-level functions were exposed in crypto.h.  Move
them into algapi.h (and internal.h).

Signed-off-by: Herbert Xu

crypto: lib/utils - Move utilities into new header

2023-03-31T09:50:09+00:00

The utilities have historically resided in algapi.h as they were
first used internally before being exported.  Move them into a
new header file so external users don't see internal API details.

Signed-off-by: Herbert Xu

crypto: api - Move MODULE_ALIAS_CRYPTO to algapi.h

2023-03-14T09:06:42+00:00

This is part of the low-level API and should not be exposed to
top-level Crypto API users.

Signed-off-by: Herbert Xu

crypto: algapi - Move stat reporting into algapi

2023-03-14T09:06:41+00:00

The stats code resurrected the unions from the early days of
kernel crypto.  This patch starts the process of moving them
out to the individual type structures as we do for everything
else.

In particular, add a report_stat function to cra_type and call
that from the stats code if available.  This allows us to move
the actual code over one-by-one.

Signed-off-by: Herbert Xu

crypto: api - Use data directly in completion function

2023-02-13T10:35:14+00:00

This patch does the final flag day conversion of all completion
functions which are now all contained in the Crypto API.

Signed-off-by: Herbert Xu

crypto: api - Add scaffolding to change completion function signature

2023-02-13T10:34:48+00:00

The crypto completion function currently takes a pointer to a
struct crypto_async_request object.  However, in reality the API
does not allow the use of any part of the object apart from the
data field.  For example, ahash/shash will create a fake object
on the stack to pass along a different data field.

This leads to potential bugs where the user may try to dereference
or otherwise use the crypto_async_request object.

This patch adds some temporary scaffolding so that the completion
function can take a void * instead.  Once affected users have been
converted this can be removed.

The helper crypto_request_complete will remain even after the
conversion is complete.  It should be used instead of calling
the completion function directly.

Signed-off-by: Herbert Xu 
Reviewed-by: Giovanni Cabiddu 
Signed-off-by: Herbert Xu