evm_fix_hmac(9)

🦋 bestie, meet evm_fix_hmac(9) 🦋

okay so this is the section 9 Kernel API Manual page for evm_fix_hmac, and it is lowkey very "kernel integrity internals" of it all. We're gonna get through it together, no cap. 💖

🌸 NAME 🌸

evm_fix_hmac — calculates the HMAC and adds it to security.evm for fix mode. That's the whole vibe: HMAC math, then it goes into security.evm because we're in fix mode. ✨

✨ SYNOPSIS ✨

int evm_fix_hmac (struct dentry *dentry , const char *xattr_name , const
       char *xattr_value , size_t xattr_value_len );

🎀 ARGUMENTS 🎀

• dentry — pointer to the affected dentry which doesn't yet have security.evm xattr. So like, this is the dentry in question, and it has not gotten its security.evm xattr yet. 🫶
• xattr_name — pointer to the affected extended attribute name. The name of the xattr that's in the mix.
• xattr_value — pointer to the new extended attribute value. The fresh value, bestie.
• xattr_value_len — pointer to the new extended attribute value length. Yep, that's the length situation exactly as the page spells it out.

💅 DESCRIPTION 💅

Expects to be called with i_mutex locked.

⚠️ okay important vibe check: this page says it expects to be called with i_mutex locked. So do not come in here unlocked and act surprised, bestie. The manual is telling you the expectation up front. 🔒

🔥 RETURN 🔥

• 0 on success. Slay, it worked. ✅
• -EPERM / -ENOMEM / -EOPNOTSUPP on failure. Those are the failure returns, and they are not cute. 😭

🌈 SEE ALSO 🌈

Kernel file: ./security/integrity/evm/evm_main.c

• evm_read_protected_xattrs(9)
• evm_verifyxattr(9)
• evm_inode_setxattr(9)
• evm_inode_removexattr(9)
• evm_inode_set_acl(9)
• evm_inode_remove_acl(9)
• evm_metadata_changed(9)
• evm_revalidate_status(9)
• evm_inode_post_setxattr(9)
• evm_inode_post_set_acl(9)
• evm_inode_post_removexattr(9)
• evm_inode_post_remove_acl(9)
• evm_inode_setattr(9)
• evm_inode_post_setattr(9)

Signed off from ./security/integrity/evm, dated October 2026, and filed under evm_fix_hmac(9) — bye bestie, go lock that i_mutex 💅✨