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Hallyn" , Roberto Sassu , David Safford , Greg Kroah-Hartman , Kees Cook , Francis Perron , linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Akrites SIRT , AutonomousCodeSecurity@microsoft.com, Cen Zhang Subject: [PATCH v2] KEYS: encrypted: fix integer overflow of datablob_len Date: Wed, 26 Aug 2026 11:44:56 -0400 Message-ID: <20260826154456.85974-1-blbllhy@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Cen Zhang (Microsoft Security FORGE Labs)" The datablob_len field in struct encrypted_key_payload and the local variable in encrypted_key_alloc() are declared as unsigned short, which has a maximum value of 65535. The datablob_len is computed as: format_len + 1 + strlen(master_desc) + 1 + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen An attacker can create an encrypted key with a very long datalen string (e.g., 32756 characters of leading zeros followed by "4096", which kstrtol() happily parses as 4096), and then update it with a very long master_desc string (~32760 characters). The combined lengths exceed 65535, causing the unsigned short to silently wrap around. This results in a grossly undersized kzalloc() allocation, and the subsequent memcpy() in __ekey_init() writes ~32KB past the end of the buffer, corrupting adjacent slab objects. Fix this by: 1. Using check_add_overflow() to calculate datablob_len directly into its existing unsigned short destination. 2. Checking the total payload length the same way before passing it to key_payload_reserve(), since key->datalen is also unsigned short. 3. Using kzalloc_flex() to allocate encrypted_key_payload together with its trailing payload_data[] array. Fixes: 7e70cb497850 ("keys: add new key-type encrypted") Cc: stable@vger.kernel.org Assisted-by: GitHub-Copilot:claude-opus-4.6 Signed-off-by: Cen Zhang (Microsoft Security FORGE Labs) Signed-off-by: Francis Perron (Akrites SIRT) --- Changes in v2: - Keep datablob_len unchanged and check both unsigned short bounds with check_add_overflow(). - Use kzalloc_flex() for the trailing payload_data[] array. - Correct the attribution and sign-off trailers. The initial version was discussed off-list and is not publicly archived. security/keys/encrypted-keys/encrypted.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c index 59cb77b237b3..e07092ea301a 100644 --- a/security/keys/encrypted-keys/encrypted.c +++ b/security/keys/encrypted-keys/encrypted.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -579,6 +580,7 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key, { struct encrypted_key_payload *epayload = NULL; unsigned short datablob_len; + unsigned short payload_totallen; unsigned short decrypted_datalen; unsigned short payload_datalen; unsigned int encrypted_datalen; @@ -632,16 +634,22 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key, encrypted_datalen = roundup(decrypted_datalen, blksize); - datablob_len = format_len + 1 + strlen(master_desc) + 1 - + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen; + if (check_add_overflow(format_len + 1 + strlen(master_desc) + 1 + + strlen(datalen) + 1 + ivsize + 1, + encrypted_datalen, &datablob_len)) + return ERR_PTR(-EINVAL); + + if (check_add_overflow(datablob_len, + payload_datalen + HASH_SIZE + 1, + &payload_totallen)) + return ERR_PTR(-EINVAL); - ret = key_payload_reserve(key, payload_datalen + datablob_len - + HASH_SIZE + 1); + ret = key_payload_reserve(key, payload_totallen); if (ret < 0) return ERR_PTR(ret); - epayload = kzalloc(sizeof(*epayload) + payload_datalen + - datablob_len + HASH_SIZE + 1, GFP_KERNEL); + epayload = kzalloc_flex(*epayload, payload_data, payload_totallen, + GFP_KERNEL); if (!epayload) return ERR_PTR(-ENOMEM); -- 2.55.0