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KEYS: Invert FINAL_PUT bit 

Invert the FINAL_PUT bit so that test_bit_acquire and clear_bit_unlock
can be used instead of smp_mb.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Herbert Xu 2025-05-28 13:18:17 +01:00 committed by Linus Torvalds
parent aef17cb3d3
commit 488ef35601
3 changed files with 6 additions and 5 deletions
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2
include/linux/key.h
View File

@ -236,7 +236,7 @@ struct key {
#define KEY_FLAG_ROOT_CAN_INVAL 7 /* set if key can be invalidated by root without permission */
#define KEY_FLAG_KEEP 8 /* set if key should not be removed */
#define KEY_FLAG_UID_KEYRING 9 /* set if key is a user or user session keyring */
#define KEY_FLAG_FINAL_PUT 10 /* set if final put has happened on key */
#define KEY_FLAG_USER_ALIVE 10 /* set if final put has not happened on key yet */
/* the key type and key description string
* - the desc is used to match a key against search criteria

4
security/keys/gc.c
View File

@ -218,8 +218,8 @@ continue_scanning:
key = rb_entry(cursor, struct key, serial_node);
cursor = rb_next(cursor);
if (test_bit(KEY_FLAG_FINAL_PUT, &key->flags)) {
smp_mb(); /* Clobber key->user after FINAL_PUT seen. */
if (!test_bit_acquire(KEY_FLAG_USER_ALIVE, &key->flags)) {
/* Clobber key->user after final put seen. */
goto found_unreferenced_key;
}

5
security/keys/key.c
View File

@ -298,6 +298,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
key->restrict_link = restrict_link;
key->last_used_at = ktime_get_real_seconds();
key->flags |= 1 << KEY_FLAG_USER_ALIVE;
if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
key->flags |= 1 << KEY_FLAG_IN_QUOTA;
if (flags & KEY_ALLOC_BUILT_IN)
@ -658,8 +659,8 @@ void key_put(struct key *key)
key->user->qnbytes -= key->quotalen;
spin_unlock_irqrestore(&key->user->lock, flags);
}
smp_mb(); /* key->user before FINAL_PUT set. */
set_bit(KEY_FLAG_FINAL_PUT, &key->flags);
/* Mark key as safe for GC after key->user done. */
clear_bit_unlock(KEY_FLAG_USER_ALIVE, &key->flags);
schedule_work(&key_gc_work);
}
}