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[68.48.65.54]) by smtp.gmail.com with ESMTPSA id af79cd13be357-92ee5b492ebsm624902185a.9.2026.07.11.18.45.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Jul 2026 18:45:17 -0700 (PDT) From: Michael Bommarito To: David Howells , Jarkko Sakkinen Cc: Paul Moore , James Morris , "Serge E . Hallyn" , Andrew Morton , keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/3] keys: fix out-of-bounds read in keyring_get_key_chunk() Date: Sat, 11 Jul 2026 21:44:58 -0400 Message-ID: <20260712014500.480410-2-michael.bommarito@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260712014500.480410-1-michael.bommarito@gmail.com> References: <20260712014500.480410-1-michael.bommarito@gmail.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit For description-level chunks keyring_get_key_chunk() advances the read pointer by level * sizeof(long) past the inline prefix but only bounds-checks the prefix, so a long enough key description is read past its kmemdup(desc, desc_len + 1) allocation. Compute the full byte offset and bounds-check the description against it before reading. The walk only reaches a description-level chunk when two keys collide through the hash, x, type and domain_tag chunks, so this is reached from an unprivileged add_key(2) with a crafted pair of same-type keys whose index hashes collide; KASAN reports a slab-out-of-bounds read. Fixes: f771fde82051 ("keys: Simplify key description management") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito --- security/keys/keyring.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) KASAN, x86_64: add_key(2) of a crafted hash-colliding "user"-key pair (~63-byte descriptions) reports BUG: KASAN: slab-out-of-bounds in keyring_get_key_chunk keyring_get_key_chunk <- assoc_array_insert <- __key_link_begin <- __do_sys_add_key reading one byte past the description allocation; the same trigger is KASAN-clean with this patch. On a kernel built without init-on-alloc, reading the colliding keyring back with KEYCTL_READ returns uninitialized slab until patches 2 and 3 are applied too. Trigger available off-list. diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 7a2ee0ded7c93..1739373172ad5 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -270,7 +270,7 @@ static unsigned long keyring_get_key_chunk(const void *data, int level) const struct keyring_index_key *index_key = data; unsigned long chunk = 0; const u8 *d; - int desc_len = index_key->desc_len, n = sizeof(chunk); + int desc_len = index_key->desc_len, n = sizeof(chunk), offset; level /= ASSOC_ARRAY_KEY_CHUNK_SIZE; switch (level) { @@ -284,12 +284,12 @@ static unsigned long keyring_get_key_chunk(const void *data, int level) return (unsigned long)index_key->domain_tag; default: level -= 4; - if (desc_len <= sizeof(index_key->desc)) + offset = sizeof(index_key->desc) + level * sizeof(long); + if (desc_len <= offset) return 0; - d = index_key->description + sizeof(index_key->desc); - d += level * sizeof(long); - desc_len -= sizeof(index_key->desc); + d = index_key->description + offset; + desc_len -= offset; if (desc_len > n) desc_len = n; do { -- 2.53.0