From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9F5615187EA; Wed, 30 Sep 2026 17:12:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790788343; cv=none; b=AwF5Vc9z62a7f1ejcE1zBCBdsKHBIQnYN2AolpNj1Eb3QzNGc1M+XLG12ylLhhUYR9aaUjbDccg/bHbn/XUyKKI6QvARVWtZ+2iXvgTTAd362vfnFc2uut4Y7Gxa5dMoqDQU59/gSiiRdeSQW39KlOT8zFv3gYTkBVknUgkiJW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790788343; c=relaxed/simple; bh=xitH/kbmXI4GKgNWKusCqgP7ZMuRGV3EmOTej7n3W4k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aLUKpqe/l3oISQtMgwocNWOt0SW8bmdnsEnkTR7s2tny1t9Rd8HSFuA15ObeFeqeuHRJtU58pMlrHzvc75yRrRB8B8FOqUSlY9yVROgIx/NVBh6EF4SIRiuZ+yLf98PO9JcTdYBQFtkxtcfLcGbOZO8EldyxejNV4w2D3iLg324= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Vz4ueHoB; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Vz4ueHoB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3E9E1F000FF; Wed, 30 Sep 2026 17:12:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790788342; bh=3sGcYnQUsNg6QmuhweavuGDKzRVVZeo/bQRa3YkppGM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Vz4ueHoBOFMjZwOqS0/BZaHI5pogVeHfC3gZdmCZn5hrtVjMTKg9d8igS9RvO6G7f AfU/joY8VGHgEO5UVmpFtKnAurmjQ5J+E1C1nqgG6A1rSENm9ZpoqBNcOd5uAqq/6d 2F5gF+ghkdENM/X/8AK1HPcy+PUK2FT/shYJQYRI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Karl Mehltretter , Jarkko Sakkinen , Sasha Levin Subject: [PATCH 6.12 091/877] keys: fix lost wakeup when reaping a dead key type Date: Wed, 30 Sep 2026 17:16:42 +0200 Message-ID: <20260930152416.701271629@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152414.738996857@linuxfoundation.org> References: <20260930152414.738996857@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Karl Mehltretter [ Upstream commit 2725ab3f5ad1c5f375c7c9fee4af02a9b138f701 ] clear_bit() is atomic with respect to the word it modifies, but it is an unordered operation: it implies no memory barrier on either side (Documentation/atomic_bitops.txt). key_garbage_collector() clears KEY_GC_REAPING_KEYTYPE with clear_bit() and calls wake_up_bit() after reaping a dead key type. wake_up_bit() uses a lockless waitqueue check and requires a full barrier after the clear. The existing smp_mb() is before clear_bit(), so nothing orders the clear against that check. The GC can see an empty waitqueue while unregister_key_type() still sees the bit set. The final wakeup is then lost, leaving module unload stuck in wait_on_bit(). Use clear_and_wake_up_bit(). Its clear_bit_unlock() has RELEASE semantics, so the completed GC work stays ordered before the clear, and its smp_mb__after_atomic() orders the clear before the waitqueue check. Fixes: 0c061b5707ab ("KEYS: Correctly destroy key payloads when their keytype is removed") Assisted-by: Claude:claude-fable-5 Signed-off-by: Karl Mehltretter Link: https://lore.kernel.org/r/20260821025327.61488-1-kmehltretter@gmail.com Reviewed-by: Jarkko Sakkinen Signed-off-by: Jarkko Sakkinen Signed-off-by: Sasha Levin --- security/keys/gc.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/security/keys/gc.c b/security/keys/gc.c index f27223ea4578f..cf71b26c0c008 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -318,9 +318,7 @@ static void key_garbage_collector(struct work_struct *work) if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) { kdebug("dead wake"); - smp_mb(); - clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); - wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE); + clear_and_wake_up_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); } if (gc_state & KEY_GC_REAP_AGAIN) -- 2.53.0