On Sun, Oct 12, 2025 at 10:38:40PM +0200, Thorsten Blum wrote:
Use check_add_overflow() to guard against a potential integer overflow when adding the binary blob lengths in asymmetric_key_generate_id() and return -EOVERFLOW accordingly. This prevents a possible buffer overflow when copying data from potentially malicious X.509 fields that can be arbitrarily large, such as ASN.1 INTEGER serial numbers, issuer names, etc.
Also use struct_size() to calculate the number of bytes to allocate for the new asymmetric key id.
Cc: stable@vger.kernel.org Fixes: 7901c1a8effb ("KEYS: Implement binary asymmetric key ID handling")
No stable designation please, this doesn't pass the "obviously correct" test, see below.
+++ b/crypto/asymmetric_keys/asymmetric_type.c @@ -141,12 +142,14 @@ struct asymmetric_key_id *asymmetric_key_generate_id(const void *val_1, size_t len_2) { struct asymmetric_key_id *kid;
- size_t len;
- kid = kmalloc(sizeof(struct asymmetric_key_id) + len_1 + len_2,
GFP_KERNEL);
- if (check_add_overflow(len_1, len_2, &len))
return ERR_PTR(-EOVERFLOW);- kid = kmalloc(struct_size(kid, data, len), GFP_KERNEL);
This will add (at least) 2 bytes to len (namely the size of struct asymmetric_key_id)) and may cause an overflow (even if len_1 + len_2 did not overflow).
struct_size() truncates to SIZE_MAX and then right below...
if (!kid) return ERR_PTR(-ENOMEM);
- kid->len = len_1 + len_2;
- kid->len = len; memcpy(kid->data, val_1, len_1); memcpy(kid->data + len_1, val_2, len_2);
... this memcpy() operation will perform an out-of-bound access beyond SIZE_MAX.
Thanks,
Lukas