From 3ceb6543e9cf6ed87cc1fbc6f23ca2db903564cd Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Fri, 23 Oct 2020 17:51:31 -0700 Subject: fscrypt: remove kernel-internal constants from UAPI header There isn't really any valid reason to use __FSCRYPT_MODE_MAX or FSCRYPT_POLICY_FLAGS_VALID in a userspace program. These constants are only meant to be used by the kernel internally, and they are defined in the UAPI header next to the mode numbers and flags only so that kernel developers don't forget to update them when adding new modes or flags. In https://lkml.kernel.org/r/20201005074133.1958633-2-satyat@google.com there was an example of someone wanting to use __FSCRYPT_MODE_MAX in a user program, and it was wrong because the program would have broken if __FSCRYPT_MODE_MAX were ever increased. So having this definition available is harmful. FSCRYPT_POLICY_FLAGS_VALID has the same problem. So, remove these definitions from the UAPI header. Replace FSCRYPT_POLICY_FLAGS_VALID with just listing the valid flags explicitly in the one kernel function that needs it. Move __FSCRYPT_MODE_MAX to fscrypt_private.h, remove the double underscores (which were only present to discourage use by userspace), and add a BUILD_BUG_ON() and comments to (hopefully) ensure it is kept in sync. Keep the old name FS_POLICY_FLAGS_VALID, since it's been around for longer and there's a greater chance that removing it would break source compatibility with some program. Indeed, mtd-utils is using it in an #ifdef, and removing it would introduce compiler warnings (about FS_POLICY_FLAGS_PAD_* being redefined) into the mtd-utils build. However, reduce its value to 0x07 so that it only includes the flags with old names (the ones present before Linux 5.4), and try to make it clear that it's now "frozen" and no new flags should be added to it. Fixes: 2336d0deb2d4 ("fscrypt: use FSCRYPT_ prefix for uapi constants") Cc: # v5.4+ Link: https://lore.kernel.org/r/20201024005132.495952-1-ebiggers@kernel.org Signed-off-by: Eric Biggers --- fs/crypto/fscrypt_private.h | 9 ++++++--- fs/crypto/keyring.c | 2 +- fs/crypto/keysetup.c | 4 +++- fs/crypto/policy.c | 5 ++++- 4 files changed, 14 insertions(+), 6 deletions(-) (limited to 'fs/crypto') diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 4f5806a3b73d..322ecae9a758 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -25,6 +25,9 @@ #define FSCRYPT_CONTEXT_V1 1 #define FSCRYPT_CONTEXT_V2 2 +/* Keep this in sync with include/uapi/linux/fscrypt.h */ +#define FSCRYPT_MODE_MAX FSCRYPT_MODE_ADIANTUM + struct fscrypt_context_v1 { u8 version; /* FSCRYPT_CONTEXT_V1 */ u8 contents_encryption_mode; @@ -491,9 +494,9 @@ struct fscrypt_master_key { * Per-mode encryption keys for the various types of encryption policies * that use them. Allocated and derived on-demand. */ - struct fscrypt_prepared_key mk_direct_keys[__FSCRYPT_MODE_MAX + 1]; - struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[__FSCRYPT_MODE_MAX + 1]; - struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[__FSCRYPT_MODE_MAX + 1]; + struct fscrypt_prepared_key mk_direct_keys[FSCRYPT_MODE_MAX + 1]; + struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[FSCRYPT_MODE_MAX + 1]; + struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[FSCRYPT_MODE_MAX + 1]; /* Hash key for inode numbers. Initialized only when needed. */ siphash_key_t mk_ino_hash_key; diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index 53cc552a7b8f..d7ec52cb3d9a 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -44,7 +44,7 @@ static void free_master_key(struct fscrypt_master_key *mk) wipe_master_key_secret(&mk->mk_secret); - for (i = 0; i <= __FSCRYPT_MODE_MAX; i++) { + for (i = 0; i <= FSCRYPT_MODE_MAX; i++) { fscrypt_destroy_prepared_key(&mk->mk_direct_keys[i]); fscrypt_destroy_prepared_key(&mk->mk_iv_ino_lblk_64_keys[i]); fscrypt_destroy_prepared_key(&mk->mk_iv_ino_lblk_32_keys[i]); diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index d595abb8ef90..31fb08d94f87 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -56,6 +56,8 @@ static struct fscrypt_mode * select_encryption_mode(const union fscrypt_policy *policy, const struct inode *inode) { + BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1); + if (S_ISREG(inode->i_mode)) return &fscrypt_modes[fscrypt_policy_contents_mode(policy)]; @@ -168,7 +170,7 @@ static int setup_per_mode_enc_key(struct fscrypt_info *ci, unsigned int hkdf_infolen = 0; int err; - if (WARN_ON(mode_num > __FSCRYPT_MODE_MAX)) + if (WARN_ON(mode_num > FSCRYPT_MODE_MAX)) return -EINVAL; prep_key = &keys[mode_num]; diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index 4441d9944b9e..faa0f21daa68 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -175,7 +175,10 @@ static bool fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 *policy, return false; } - if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) { + if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK | + FSCRYPT_POLICY_FLAG_DIRECT_KEY | + FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 | + FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) { fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)", policy->flags); return false; -- cgit v1.2.3