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fscrypt: Replace some variable-size memsets with fixed-size

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For zeroing IVs and raw keys, remove the misguided optimization of
zeroing the actual size used (typically 16 and 64 bytes respectively)
instead of the max size (32 and 64 bytes respectively).  Using a
compile-time constant size allows the compiler to specialize the memset
for that size (typically by inlining a few 'mov' instructions), which
is more important than zeroing a few extra bytes with these small sizes.

Link: https://patch.msgid.link/20260718205606.50713-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
This commit is contained in:
Eric Biggers 2026-07-18 13:56:06 -07:00
parent b3aa5b308c
commit f5bd17a8b5
3 changed files with 4 additions and 4 deletions
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2
fs/crypto/crypto.c
View File

@ -83,7 +83,7 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index,
{
u8 flags = fscrypt_policy_flags(&ci->ci_policy);
memset(iv, 0, ci->ci_mode->ivsize);
memset(iv, 0, sizeof(*iv));
if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
WARN_ON_ONCE(index > U32_MAX);

4
fs/crypto/keysetup.c
View File

@ -267,7 +267,7 @@ static int setup_per_mode_enc_key(struct fscrypt_inode_info *ci,
hkdf_info, hkdf_infolen, raw_mode_key,
mode->keysize);
err = fscrypt_prepare_key(prep_key, raw_mode_key, ci);
memzero_explicit(raw_mode_key, mode->keysize);
memzero_explicit(raw_mode_key, sizeof(raw_mode_key));
}
if (err) {
kfree(new_node);
@ -397,7 +397,7 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_inode_info *ci,
ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
derived_key, ci->ci_mode->keysize);
err = fscrypt_set_per_file_enc_key(ci, derived_key);
memzero_explicit(derived_key, ci->ci_mode->keysize);
memzero_explicit(derived_key, sizeof(derived_key));
}
if (err)
return err;

2
fs/crypto/keysetup_v1.c
View File

@ -251,7 +251,7 @@ static int setup_v1_file_key_derived(struct fscrypt_inode_info *ci,
err = fscrypt_set_per_file_enc_key(ci, derived_key);
memzero_explicit(derived_key, derived_keysize);
memzero_explicit(derived_key, sizeof(derived_key));
/* No need to zeroize 'aes', as its key is not secret. */
return err;
}