forked from Minki/linux
keys: Handle there being no fallback destination keyring for request_key()
When request_key() is called, without there being any standard process keyrings on which to fall back if a destination keyring is not specified, an oops is liable to occur when construct_alloc_key() calls down_write() on dest_keyring's semaphore. Due to function inlining this may be seen as an oops in down_write() as called from request_key_and_link(). This situation crops up during boot, where request_key() is called from within the kernel (such as in CIFS mounts) where nobody is actually logged in, and so PAM has not had a chance to create a session keyring and user keyrings to act as the fallback. To fix this, make construct_alloc_key() not attempt to cache a key if there is no fallback key if no destination keyring is given specifically. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -311,6 +311,7 @@ static int construct_alloc_key(struct key_type *type,
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set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
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if (dest_keyring)
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down_write(&dest_keyring->sem);
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/* attach the key to the destination keyring under lock, but we do need
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@ -322,9 +323,11 @@ static int construct_alloc_key(struct key_type *type,
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if (!IS_ERR(key_ref))
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goto key_already_present;
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if (dest_keyring)
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__key_link(dest_keyring, key);
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mutex_unlock(&key_construction_mutex);
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if (dest_keyring)
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up_write(&dest_keyring->sem);
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mutex_unlock(&user->cons_lock);
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*_key = key;
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