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authorOndrej Kozina <okozina@redhat.com>2017-01-31 15:47:11 +0100
committerMike Snitzer <snitzer@redhat.com>2017-02-03 10:26:14 -0500
commitf5b0cba8f23915e92932f11eb063e37d70556a89 (patch)
tree19f7ccac636459333cca52027914d19084b1392b /drivers/md/dm-crypt.c
parent4087a1fffe38106e10646606a27f10d40451862d (diff)
dm crypt: replace RCU read-side section with rwsem
The lockdep splat below hints at a bug in RCU usage in dm-crypt that was introduced with commit c538f6ec9f56 ("dm crypt: add ability to use keys from the kernel key retention service"). The kernel keyring function user_key_payload() is in fact a wrapper for rcu_dereference_protected() which must not be called with only rcu_read_lock() section mark. Unfortunately the kernel keyring subsystem doesn't currently provide an interface that allows the use of an RCU read-side section. So for now we must drop RCU in favour of rwsem until a proper function is made available in the kernel keyring subsystem. =============================== [ INFO: suspicious RCU usage. ] 4.10.0-rc5 #2 Not tainted ------------------------------- ./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 2 locks held by cryptsetup/6464: #0: (&md->type_lock){+.+.+.}, at: [<ffffffffa02472a2>] dm_lock_md_type+0x12/0x20 [dm_mod] #1: (rcu_read_lock){......}, at: [<ffffffffa02822f8>] crypt_set_key+0x1d8/0x4b0 [dm_crypt] stack backtrace: CPU: 1 PID: 6464 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 ? ____fput+0x9/0x10 ? task_work_run+0x7e/0xa0 ? trace_hardirqs_on_caller+0x122/0x1b0 SyS_ioctl+0x3c/0x70 entry_SYSCALL_64_fastpath+0x18/0xad RIP: 0033:0x7f392c9a4ec7 RSP: 002b:00007ffef6383378 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007ffef63830a0 RCX: 00007f392c9a4ec7 RDX: 000000000124fcc0 RSI: 00000000c138fd09 RDI: 0000000000000005 RBP: 00007ffef6383090 R08: 00000000ffffffff R09: 00000000012482b0 R10: 2a28205d34383336 R11: 0000000000000246 R12: 00007f392d803a08 R13: 00007ffef63831e0 R14: 0000000000000000 R15: 00007f392d803a0b Fixes: c538f6ec9f56 ("dm crypt: add ability to use keys from the kernel key retention service") Reported-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Ondrej Kozina <okozina@redhat.com> Reviewed-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-crypt.c')
-rw-r--r--drivers/md/dm-crypt.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 7c6c57216bf2..8a9f742d8ed7 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1534,18 +1534,18 @@ static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string
return PTR_ERR(key);
}
- rcu_read_lock();
+ down_read(&key->sem);
ukp = user_key_payload(key);
if (!ukp) {
- rcu_read_unlock();
+ up_read(&key->sem);
key_put(key);
kzfree(new_key_string);
return -EKEYREVOKED;
}
if (cc->key_size != ukp->datalen) {
- rcu_read_unlock();
+ up_read(&key->sem);
key_put(key);
kzfree(new_key_string);
return -EINVAL;
@@ -1553,7 +1553,7 @@ static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string
memcpy(cc->key, ukp->data, cc->key_size);
- rcu_read_unlock();
+ up_read(&key->sem);
key_put(key);
/* clear the flag since following operations may invalidate previously valid key */