Re: [PATCH v2 13/13] lib/crypto: Add documentation about zeroization of key and context data
From: Jonathan Corbet <corbet@lwn.net>
Date: 2026-09-09 13:22:13
Also in:
linux-crypto, lkml
Thomas Huth [off-list ref] writes:
Add a central document about zeroization in libcrypto so we don't have to repeat this information in the individual kernel docs of the zeroization functions all over the place. Signed-off-by: Thomas Huth <redacted> --- .../crypto/libcrypto-zeroization.rst | 129 ++++++++++++++++++ Documentation/crypto/libcrypto.rst | 1 + 2 files changed, 130 insertions(+) create mode 100644 Documentation/crypto/libcrypto-zeroization.rst
One nit...
quoted hunk ↗ jump to hunk
diff --git a/Documentation/crypto/libcrypto-zeroization.rst b/Documentation/crypto/libcrypto-zeroization.rst new file mode 100644 index 0000000000000..ba9b05320ad53 --- /dev/null +++ b/Documentation/crypto/libcrypto-zeroization.rst@@ -0,0 +1,129 @@ +.. SPDX-License-Identifier: GPL-2.0-or-later + +Crypto Key Zeroization +====================== + +This document describes the conventions for zeroizing crypto structures in the +kernel. + +.. contents:: + +Overview +-------- + +Cryptographic key material and intermediate state (such as HMAC contexts) must +be zeroized after use to prevent sensitive data from lingering on the stack or +heap, where it could be leaked through memory disclosure vulnerabilities, +crash dumps, or cold-boot attacks. + +For memory that has been allocated with kmalloc() or a similar function, +kfree_sensitive() should be used instead of kfree() to release the memory. + +For other cases, the kernel provides ``memzero_explicit()`` for clearing the +memory. Unlike plain ``memset()``, ``memzero_explicit()`` is guaranteed not +to be optimized away by the compiler, even when the memory being cleared +appears to be dead.
Don't mark up function names, just say memzero_explicit(). The automarkup code will then do the right thing, including cross-references when the functions have kerneldoc documentation. Thanks, jon