I'm using linux on an embedded target in a Hardware Security Module-like application. One requirement is that I want the system to be able to quickly erase its memory when it detects physical tampering. I'm approaching that by using kdump to load into a small payload that instead of dumping RAM, erases RAM from start to end. However, writing all of RAM, especially on an embedded target, is rather slow. For this reason, I propose the mechanism in this patch series:
Add CONFIG_CRASH_ZEROIZE (default off), which when enabled makes various subsystems handling secret data do a quick, targeted wipe of these secrets before kdump. This behavior might also be interesting in cases where you run a normal kdump kernel but you still want to keep things like fde crypto keys out of these dumps. CONFIG_CRASH_ZEROIZE is a best effort, defense in depth solution. There are circumstances, such as when a panic is triggered after memory corruption, or when a panic interrupts some operation that mutates data structures under locks, when the kernel cannot safely wipe some memory areas. The handlers proposed in this series will just print a warning and skip the affected areas in this case. This series introduces handlers for the major locations I found where having this sort of thing makes sense. Notable omissions right now are the Ceph and CIFS subsystems. I have WIP patches for these, but since I can't easily test them right now, I omitted them from this patch set for now. Currently included locations are: * various key types in security/keys * rxrpc * fscrypt * dm-crypt * crypto tfm instances * secretmem (which I'm going to start using in my application) I've verified this patch series on an ARM64 target using the helper code at https://codeberg.org/yasec/crash-wipe-test . This code stuffs the affected kernel subsystems with keys and secret data, then crashes the system, takes a RAM dump and verifies the dump is clean of secrets. Note that the helper code is partially LLM-generated, so read with care. It passes a positive control test with the config option disabled. The patch series applies on top of linux-next but should work on 7.0.0, too. I've tested the patches on a Arduino uno Q (Qualcomm QRB2210, ARM64) embedded target. Signed-off-by: Jan Sebastian Götte <[email protected]> --- Changes in v2: - New keyring key types - New handlers: rxrpc, fscrypt, dm-crypt and crypto tfm - Renamed from "zeroize" to "wipe" - Add ARM64-specific cache flush logic - Link to v1: https://patch.msgid.link/[email protected] To: Andrew Morton <[email protected]> To: Baoquan He <[email protected]> To: Mike Rapoport <[email protected]> To: Pasha Tatashin <[email protected]> To: Pratyush Yadav <[email protected]> To: Dave Young <[email protected]> To: Catalin Marinas <[email protected]> To: Will Deacon <[email protected]> To: David Howells <[email protected]> To: Jarkko Sakkinen <[email protected]> To: Jonathan Corbet <[email protected]> To: Shuah Khan <[email protected]> To: Paul Moore <[email protected]> To: James Morris <[email protected]> To: "Serge E. Hallyn" <[email protected]> To: Lukas Wunner <[email protected]> To: Ignat Korchagin <[email protected]> To: Herbert Xu <[email protected]> To: "David S. Miller" <[email protected]> To: Keith Busch <[email protected]> To: Jens Axboe <[email protected]> To: Christoph Hellwig <[email protected]> To: Sagi Grimberg <[email protected]> To: Trond Myklebust <[email protected]> To: Anna Schumaker <[email protected]> To: Mimi Zohar <[email protected]> To: James Bottomley <[email protected]> To: Marc Dionne <[email protected]> To: Eric Dumazet <[email protected]> To: Jakub Kicinski <[email protected]> To: Paolo Abeni <[email protected]> To: Simon Horman <[email protected]> To: Eric Biggers <[email protected]> To: "Theodore Y. Ts'o" <[email protected]> To: Jaegeuk Kim <[email protected]> To: Alexander Viro <[email protected]> To: Christian Brauner <[email protected]> To: Jan Kara <[email protected]> To: Alasdair Kergon <[email protected]> To: Mike Snitzer <[email protected]> To: Mikulas Patocka <[email protected]> To: Benjamin Marzinski <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] --- Jan Sebastian Götte (13): kexec: add CRASH_WIPE_SECRETS to wipe secrets before kdump crash-core: Flush caches on CRASH_WIPE_SECRETS arm64/mm: add set_direct_map_default_nosplit() mm/secretmem: wipe secret pages before kdump security/keys: wipe key payloads before kdump security/keys: implement wipe op for user-type keys security/keys: implement wipe op for big_key security/keys: implement wipe op for trusted and encrypted keys security/keys: implement wipe op for asymmetric keys rxrpc: implement wipe op for rxrpc keys fscrypt: wipe master keys before kdump crypto: api - wipe tfm contexts before kdump dm crypt: wipe key material before kdump Documentation/security/keys/core.rst | 13 +++ arch/arm64/include/asm/set_memory.h | 2 + arch/arm64/kernel/machine_kexec.c | 20 ++++ arch/arm64/mm/pageattr.c | 21 +++++ crypto/api.c | 78 +++++++++++++-- crypto/asymmetric_keys/asymmetric_type.c | 11 +++ crypto/asymmetric_keys/pkcs7_key_type.c | 1 + crypto/asymmetric_keys/public_key.c | 15 +++ drivers/md/dm-crypt.c | 151 ++++++++++++++++++++++++++---- drivers/nvme/common/keyring.c | 1 + fs/crypto/block.c | 10 ++ fs/crypto/fscrypt_private.h | 15 +++ fs/crypto/keyring.c | 68 +++++++++++++- fs/crypto/keysetup_v1.c | 15 +++ fs/nfs/nfs4idmap.c | 2 + fs/super.c | 29 ++++++ include/keys/asymmetric-subtype.h | 5 + include/keys/user-type.h | 1 + include/linux/crash_core.h | 37 ++++++++ include/linux/crypto.h | 11 +++ include/linux/fs.h | 4 + include/linux/key-type.h | 9 ++ include/linux/set_memory.h | 17 +++- kernel/Kconfig.kexec | 16 ++++ kernel/crash_core.c | 52 ++++++++++ mm/secretmem.c | 53 +++++++++++ net/rxrpc/ar-internal.h | 5 + net/rxrpc/key.c | 34 +++++++ net/rxrpc/rxgk.c | 11 +++ net/rxrpc/rxkad.c | 14 +++ net/rxrpc/server_key.c | 11 +++ security/keys/big_key.c | 17 ++++ security/keys/encrypted-keys/encrypted.c | 13 +++ security/keys/key.c | 43 +++++++++ security/keys/trusted-keys/trusted_core.c | 15 +++ security/keys/user_defined.c | 15 +++ 36 files changed, 808 insertions(+), 27 deletions(-) --- base-commit: a0dbb7d3457bdebe2dbe198bd08bf9690be5f1ec change-id: 20260811-crash-zeroize-rework-bb1a5d917577 Best regards, -- Jan Sebastian Götte <[email protected]>
