This fixes following lockdep splat emerging on
table load with a key in kernel keyring service.
In fact it hints a bug in RCU usage in dm-crypt since
kernel keyring fn user_key_payload() is in fact a wrapper
for rcu_dereference_protected() which must not be used
with only rcu_read_lock() mark.
===============================
[ INFO: suspicious RCU usage. ]
4.10.0-rc5 #2 Not tainted
-------------------------------
./include/keys/user-type.h:53 suspicious usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
2 locks held by cryptsetup/5555:
#0: (&md->type_lock){+.+.+.}, at: [<ffffffffa02472a2>] dm_lock_md_type+0x12/0x20 [dm_mod]
#1: (rcu_read_lock){......}, at: [<ffffffffa026b2f8>] crypt_set_key+0x1d8/0x4b0 [dm_crypt]
stack backtrace:
CPU: 1 PID: 5555 Comm: cryptsetup Not tainted 4.10.0-rc5 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
Call Trace:
dump_stack+0x67/0x92
lockdep_rcu_suspicious+0xc5/0x100
crypt_set_key+0x351/0x4b0 [dm_crypt]
? crypt_set_key+0x1d8/0x4b0 [dm_crypt]
crypt_ctr+0x341/0xa53 [dm_crypt]
dm_table_add_target+0x147/0x330 [dm_mod]
table_load+0x111/0x350 [dm_mod]
? retrieve_status+0x1c0/0x1c0 [dm_mod]
ctl_ioctl+0x1f5/0x510 [dm_mod]
dm_ctl_ioctl+0xe/0x20 [dm_mod]
do_vfs_ioctl+0x8e/0x690
? task_work_run+0x7e/0xa0
? trace_hardirqs_on_caller+0x122/0x1b0
SyS_ioctl+0x3c/0x70
entry_SYSCALL_64_fastpath+0x18/0xad
RIP: 0033:0x7f1be07ceec7
RSP: 002b:00007fff38c094d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000d4dbae9 RCX: 00007f1be07ceec7
RDX: 0000000001768100 RSI: 00000000c138fd09 RDI: 0000000000000005
RBP: 0000000000000006 R08: 00000000ffffffff R09: 00000000017623f0
R10: 2a28205d34383336 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fff38c0987c R14: 00007fff38c097ec R15: 0000000000000000
Reported-by: Milan Broz <mbroz@xxxxxxxxxx>
Fixes: c538f6ec9f56 (dm crypt: add ability to use keys from the kernel key retention service)
Signed-off-by: Ondrej Kozina <okozina@xxxxxxxxxx>
---
drivers/md/dm-crypt.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 7c6c572..37d5027 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -31,6 +31,7 @@
#include <crypto/md5.h>
#include <crypto/algapi.h>
#include <crypto/skcipher.h>
+#include <linux/rcupdate.h>
#include <keys/user-type.h>
#include <linux/device-mapper.h>
@@ -1498,6 +1499,12 @@ static bool contains_whitespace(const char *str)
return false;
}
+/* workaround for missing RCU read key payload wrapper */
+static const struct user_key_payload *_user_key_payload(const struct key *key)
+{
+ return (const struct user_key_payload *) rcu_dereference(key->payload.rcu_data0);
+}
+
static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string)
{
char *new_key_string, *key_desc;
@@ -1536,7 +1543,7 @@ static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string
rcu_read_lock();
- ukp = user_key_payload(key);
+ ukp = _user_key_payload(key);
if (!ukp) {
rcu_read_unlock();
key_put(key);
--
2.7.4
--
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