[PATCH 6.18 645/752] crash_dump: fix dm_crypt keys locking and ref leak

Sasha Levin
2026-02-28T17:57:40Z

From: Vasily Gorbik <gor@linux.ibm.com>

[ Upstream commit 96a54b8ffc8c4567c32fe0b6996669f1132b026d ]

crash_load_dm_crypt_keys() reads dm-crypt volume keys from the user
keyring. It uses user_key_payload_locked() without holding key->sem,
which makes lockdep complain when kexec_file_load() assembles the crash
image:

=============================
WARNING: suspicious RCU usage
-----------------------------
./include/keys/user-type.h:53 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
no locks held by kexec/4875.

stack backtrace:
Call Trace:
<TASK>
dump_stack_lvl+0x5d/0x80
lockdep_rcu_suspicious.cold+0x4e/0x96
crash_load_dm_crypt_keys+0x314/0x390
bzImage64_load+0x116/0x9a0
? __lock_acquire+0x464/0x1ba0
__do_sys_kexec_file_load+0x26a/0x4f0
do_syscall_64+0xbd/0x430
entry_SYSCALL_64_after_hwframe+0x77/0x7f

In addition, the key returned by request_key() is never key_put()'d,
leaking a key reference on each load attempt.

Take key->sem while copying the payload and drop the key reference
afterwards.

Link: https://lkml.kernel.org/r/patch.git-2d4d76083a5c.your-ad-here.call-01769426386-ext-2560@work.hours
Fixes: 479e58549b0f ("crash_dump: store dm crypt keys in kdump reserved memory")
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Coiby Xu <coxu@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/crash_dump_dm_crypt.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
index 401423ba477da..abb307a23de33 100644
--- a/kernel/crash_dump_dm_crypt.c
+++ b/kernel/crash_dump_dm_crypt.c
@@ -143,6 +143,7 @@ static int read_key_from_user_keying(struct dm_crypt_key *dm_key)
{
const struct user_key_payload *ukp;
struct key *key;
+ int ret = 0;

kexec_dprintk("Requesting logon key %s", dm_key->key_desc);
key = request_key(&key_type_logon, dm_key->key_desc, NULL);
@@ -152,20 +153,28 @@ static int read_key_from_user_keying(struct dm_crypt_key *dm_key)
return PTR_ERR(key);
}

+ down_read(&key->sem);
ukp = user_key_payload_locked(key);
- if (!ukp)
- return -EKEYREVOKED;
+ if (!ukp) {
+ ret = -EKEYREVOKED;
+ goto out;
+ }

if (ukp->datalen > KEY_SIZE_MAX) {
pr_err("Key size %u exceeds maximum (%u)\n", ukp->datalen, KEY_SIZE_MAX);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}

memcpy(dm_key->data, ukp->data, ukp->datalen);
dm_key->key_size = ukp->datalen;
kexec_dprintk("Get dm crypt key (size=%u) %s: %8ph\n", dm_key->key_size,
dm_key->key_desc, dm_key->data);
- return 0;
+
+out:
+ up_read(&key->sem);
+ key_put(key);
+ return ret;
}

struct config_key {
--
2.51.0