On Wed, Sep 09, 2026 at 11:34:33AM -0400, Cen Zhang wrote:
> encrypted_key_alloc() stores datablob_len in a u16. It is computed from
> multiple string and payload lengths. If the result exceeds U16_MAX, the
> assignment truncates the allocation size. KASAN reports a 32760-byte
> slab-out-of-bounds write when __ekey_init() copies the master key
> description into the undersized buffer.
>
> The total payload length stored in key->datalen is also a u16. Use
> check_add_overflow() to reject values that do not fit either destination,
> and use kzalloc_flex() for the flexible-array allocation.
>
> Fixes: 7e70cb497850 ("keys: add new key-type encrypted")
> Cc: [email protected]
> Link:
> https://lore.kernel.org/keyrings/[email protected]/
> Assisted-by: GitHub-Copilot:claude-opus-4.6
> Signed-off-by: Cen Zhang <[email protected]>
> Signed-off-by: Francis Perron <[email protected]>
> ---
> Changes in v3:
> - Describe the bounds using u16 and U16_MAX and simplify the commit
> message.
> - Include the KASAN-reported write size.
> - Remove organization names from the author and sign-off identities.
> - Remove the unnecessary off-list discussion note.
> - Use [email protected].
> - No code changes.
>
> 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 <linux/parser.h>
> #include <linux/string.h>
> #include <linux/err.h>
> +#include <linux/overflow.h>
> #include <keys/user-type.h>
> #include <keys/trusted-type.h>
> #include <keys/encrypted-type.h>
> @@ -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);
>
>
> base-commit: 893e11787f78e43b534e252249ac3fff4d1333f8
> --
> 2.55.0
Thanks!
Reviewed-by: Jarkko Sakkinen <[email protected]>
BR, Jarkko
