diff options
| author | 성병찬 <tjdqudcks0424@naver.com> | 2026-09-30 13:18:01 +0900 |
|---|---|---|
| committer | Jarkko Sakkinen <jarkko@kernel.org> | 2026-10-04 21:09:32 +0300 |
| commit | dd3ea3fcba7c75493760cdbccd35f029597e8d5e (patch) | |
| tree | eec349d2859f3c3951d36964ae37c4072df7630e | |
| parent | 25bf14f817168079f731975b8998fc2af380f29e (diff) | |
KEYS: Fix add_key() race with keyring restriction
__key_create_or_update() snapshots keyring->restrict_link before taking
the destination keyring's semaphore. keyring_restrict() installs a
restriction while holding that semaphore.
This allows a writer to observe no restriction, wait for the keyring
owner to install a reject-all restriction and return successfully, and
then link a key using the stale NULL snapshot. The writer only needs
write permission on the destination keyring.
Move the restrict_link read after __key_link_lock() and
__key_link_begin(). The read and the subsequent restriction check are
then serialized with restriction installation by keyring->sem.
The race was reproduced on v7.2.8 in 19 executions where restriction
installation returned before the link completed. All 19 linked the key
despite the reject-all restriction. With this change, 312 executions
reached the same ordering and every add_key() call failed with -EPERM.
The issue was found by manual concurrency analysis assisted by AI-based
analysis and independently verified with a QEMU reproducer and kernel
instrumentation.
Fixes: 5ac7eace2d00 ("KEYS: Add a facility to restrict new links into a keyring")
Cc: stable@vger.kernel.org
Signed-off-by: 성병찬 <tjdqudcks0424@naver.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/r/20260930041802.6114-1-tjdqudcks0424@naver.com
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
| -rw-r--r-- | security/keys/key.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/security/keys/key.c b/security/keys/key.c index b34a64d81d47..a438c4508595 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -840,9 +840,6 @@ static key_ref_t __key_create_or_update(key_ref_t keyring_ref, key_check(keyring); - if (!(flags & KEY_ALLOC_BYPASS_RESTRICTION)) - restrict_link = keyring->restrict_link; - key_ref = ERR_PTR(-ENOTDIR); if (keyring->type != &key_type_keyring) goto error_put_type; @@ -880,6 +877,9 @@ static key_ref_t __key_create_or_update(key_ref_t keyring_ref, goto error_link_end; } + if (!(flags & KEY_ALLOC_BYPASS_RESTRICTION)) + restrict_link = keyring->restrict_link; + if (restrict_link && restrict_link->check) { ret = restrict_link->check(keyring, index_key.type, &prep.payload, restrict_link->key); |