Hi Fabrice, > On 19.07.2026, at 18:41, Fabrice Derepas <[email protected]> > wrote: > Two correctness and type-hygiene issues exist in the DCP trusted keys > implementation. > > First, trusted_dcp_unseal() reads p->key_len from a user-supplied blob > without checking if it exceeds MAX_KEY_SIZE. If a crafted blob provides > a payload_len larger than 128, the subsequent do_aead_crypto() call > writes past the end of the p->key array into the adjacent p->blob > buffer within the same struct trusted_key_payload -- the caller's own > input, not unrelated kernel memory. While not exploitable, this > violates strict array bounds and triggers static analyzers. Fix this by > adding a validation check against > MIN_KEY_SIZE and MAX_KEY_SIZE immediately after reading the length, > matching the checks already done in trusted_core.c. > > Second, calc_blob_len() calculates a sum in size_t that truncates to > unsigned int on 64-bit platforms. Because the DCP hardware is only > present on 32-bit i.MX SoC platforms, size_t and unsigned int are > functionally equivalent in production, making this truncation harmless in > practice. Nevertheless, updating the return type to size_t (and > subsequently updating 'blen' in the seal/unseal paths) resolves > type-narrowing warnings and improves overall code hygiene. > > Fixes: 2e8a0f40a39c ("KEYS: trusted: Introduce NXP DCP-backed trusted keys") > Signed-off-by: Fabrice Derepas <[email protected]> > --- > Changes in v2: > - Reframed commit message as correctness/hardening fix (Richard, Jarkko) > - Changed bare return -EINVAL to goto out for consistency > - Added Fixes tag > > Compile-tested with arm-linux-gnueabihf-gcc on imx_v6_v7_defconfig > with CONFIG_TRUSTED_KEYS_DCP=y (W=1, zero warnings). No DCP hardware > available for runtime testing. > > security/keys/trusted-keys/trusted_dcp.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/security/keys/trusted-keys/trusted_dcp.c > b/security/keys/trusted-keys/trusted_dcp.c > index 7b6eb655d..c078adebe 100644 > --- a/security/keys/trusted-keys/trusted_dcp.c > +++ b/security/keys/trusted-keys/trusted_dcp.c > @@ -69,7 +69,7 @@ static bool skip_zk_test; > module_param_named(dcp_skip_zk_test, skip_zk_test, bool, 0); > MODULE_PARM_DESC(dcp_skip_zk_test, "Don't test whether device keys are > zero'ed"); > > -static unsigned int calc_blob_len(unsigned int payload_len) > +static size_t calc_blob_len(unsigned int payload_len) > { > return sizeof(struct dcp_blob_fmt) + payload_len + DCP_BLOB_AUTHLEN; > } > @@ -200,7 +200,8 @@ static int encrypt_blob_key(u8 *plain_key, u8 > *encrypted_key) > static int trusted_dcp_seal(struct trusted_key_payload *p, char *datablob) > { > struct dcp_blob_fmt *b = (struct dcp_blob_fmt *)p->blob; > - int blen, ret; > + size_t blen; > + int ret; > u8 *plain_blob_key; > > blen = calc_blob_len(p->key_len); > @@ -242,7 +243,8 @@ static int trusted_dcp_seal(struct trusted_key_payload > *p, char *datablob) > static int trusted_dcp_unseal(struct trusted_key_payload *p, char *datablob) > { > struct dcp_blob_fmt *b = (struct dcp_blob_fmt *)p->blob; > - int blen, ret; > + size_t blen; > + int ret; > u8 *plain_blob_key = NULL; > > if (b->fmt_version != DCP_BLOB_VERSION) { > @@ -253,9 +255,14 @@ static int trusted_dcp_unseal(struct trusted_key_payload > *p, char *datablob) > } > > p->key_len = le32_to_cpu(b->payload_len); > + if (p->key_len < MIN_KEY_SIZE || p->key_len > MAX_KEY_SIZE) { > + ret = -EINVAL; > + goto out; > + } > + > blen = calc_blob_len(p->key_len); > if (blen != p->blob_len) { > - pr_err("DCP blob has bad length: %i != %i\n", blen, > + pr_err("DCP blob has bad length: %zu != %u\n", blen, > p->blob_len); > ret = -EINVAL; > goto out; > > base-commit: 6d41c11ef3044788902a05e292cd7f0a9c7a8157 > -- > 2.53.0 >
LGTM and thanks for the fix! Reviewed-by: David Gstir <[email protected]> - David
