From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A34541C549E; Wed, 19 Mar 2025 14:34:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742394869; cv=none; b=Sbm7SSt4AUxwcBRsq18WLREOXEnAmCm40dLvrQe6IBmje51Atx6UOemT0iZyYO+6Z7Y6MI0BEqaGbvk4LSPkyI4dltpXM6kqNzOWvr8qoVP2LCzfLVTqBi5HXWqhzQH52wX1yBe9zu/E/zIOaFsfLIfAwg0MzmvUTou8SbTLDHE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742394869; c=relaxed/simple; bh=tN6icY64IwBxyikVGg7tzGOQUUa39s857vFPKP23/2s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=K4iEp5P0p5XHmwCpK8gK65mHuS1zSA0G0NmHfbvHbyWxv00AjrwCc0uRX/HQAXWsf0JYfgZK5zXOMP6NHEbUDag+vLcmFbIMzcZ//dQREqKA8R137JPeQHZKI5f9y8WlRIfNvwQ3oIv8M1EDmA/yDvUqcJEcb1HY+XjcQoz8iZQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1KJlBwG8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1KJlBwG8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D2B4C4CEE4; Wed, 19 Mar 2025 14:34:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1742394869; bh=tN6icY64IwBxyikVGg7tzGOQUUa39s857vFPKP23/2s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1KJlBwG8Eo0rfOAaT6D6RVkMY1bfOVgTg/oiZdBth5nF68cExeaRUnwurKSPp4BIO zmezwuEv65s3q7Ve9lpB8Ml18Xvti0Aa65PvvZ/bTcxx6FEC4CEUPnsoP+MmLnDwda c1BFePFafQM1Jw5R3VKwBNpmg+nThzG90vFDg6qo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jann Horn , Jens Axboe , Thomas Gleixner , Sasha Levin Subject: [PATCH 6.13 061/241] futex: Pass in task to futex_queue() Date: Wed, 19 Mar 2025 07:28:51 -0700 Message-ID: <20250319143029.238400214@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250319143027.685727358@linuxfoundation.org> References: <20250319143027.685727358@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jens Axboe [ Upstream commit 5e0e02f0d7e52cfc8b1adfc778dd02181d8b47b4 ] futex_queue() -> __futex_queue() uses 'current' as the task to store in the struct futex_q->task field. This is fine for synchronous usage of the futex infrastructure, but it's not always correct when used by io_uring where the task doing the initial futex_queue() might not be available later on. This doesn't lead to any issues currently, as the io_uring side doesn't support PI futexes, but it does leave a potentially dangling pointer which is never a good idea. Have futex_queue() take a task_struct argument, and have the regular callers pass in 'current' for that. Meanwhile io_uring can just pass in NULL, as the task should never be used off that path. In theory req->tctx->task could be used here, but there's no point populating it with a task field that will never be used anyway. Reported-by: Jann Horn Signed-off-by: Jens Axboe Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/22484a23-542c-4003-b721-400688a0d055@kernel.dk Signed-off-by: Sasha Levin --- io_uring/futex.c | 2 +- kernel/futex/core.c | 5 +++-- kernel/futex/futex.h | 11 ++++++++--- kernel/futex/pi.c | 2 +- kernel/futex/waitwake.c | 4 ++-- 5 files changed, 15 insertions(+), 9 deletions(-) diff --git a/io_uring/futex.c b/io_uring/futex.c index e29662f039e1a..f108da4ff863c 100644 --- a/io_uring/futex.c +++ b/io_uring/futex.c @@ -349,7 +349,7 @@ int io_futex_wait(struct io_kiocb *req, unsigned int issue_flags) hlist_add_head(&req->hash_node, &ctx->futex_list); io_ring_submit_unlock(ctx, issue_flags); - futex_queue(&ifd->q, hb); + futex_queue(&ifd->q, hb, NULL); return IOU_ISSUE_SKIP_COMPLETE; } diff --git a/kernel/futex/core.c b/kernel/futex/core.c index ebdd76b4ecbba..3db8567f5a44e 100644 --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -532,7 +532,8 @@ void futex_q_unlock(struct futex_hash_bucket *hb) futex_hb_waiters_dec(hb); } -void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb) +void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb, + struct task_struct *task) { int prio; @@ -548,7 +549,7 @@ void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb) plist_node_init(&q->list, prio); plist_add(&q->list, &hb->chain); - q->task = current; + q->task = task; } /** diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h index 99b32e728c4ad..6b2f4c7eb720f 100644 --- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -285,13 +285,15 @@ static inline int futex_get_value_locked(u32 *dest, u32 __user *from) } extern void __futex_unqueue(struct futex_q *q); -extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb); +extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb, + struct task_struct *task); extern int futex_unqueue(struct futex_q *q); /** * futex_queue() - Enqueue the futex_q on the futex_hash_bucket * @q: The futex_q to enqueue * @hb: The destination hash bucket + * @task: Task queueing this futex * * The hb->lock must be held by the caller, and is released here. A call to * futex_queue() is typically paired with exactly one call to futex_unqueue(). The @@ -299,11 +301,14 @@ extern int futex_unqueue(struct futex_q *q); * or nothing if the unqueue is done as part of the wake process and the unqueue * state is implicit in the state of woken task (see futex_wait_requeue_pi() for * an example). + * + * Note that @task may be NULL, for async usage of futexes. */ -static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb) +static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb, + struct task_struct *task) __releases(&hb->lock) { - __futex_queue(q, hb); + __futex_queue(q, hb, task); spin_unlock(&hb->lock); } diff --git a/kernel/futex/pi.c b/kernel/futex/pi.c index d62cca5ed8f4c..635c7d5d42220 100644 --- a/kernel/futex/pi.c +++ b/kernel/futex/pi.c @@ -982,7 +982,7 @@ int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int tryl /* * Only actually queue now that the atomic ops are done: */ - __futex_queue(&q, hb); + __futex_queue(&q, hb, current); if (trylock) { ret = rt_mutex_futex_trylock(&q.pi_state->pi_mutex); diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c index 3a10375d95218..a9056acb75eef 100644 --- a/kernel/futex/waitwake.c +++ b/kernel/futex/waitwake.c @@ -350,7 +350,7 @@ void futex_wait_queue(struct futex_hash_bucket *hb, struct futex_q *q, * access to the hash list and forcing another memory barrier. */ set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE); - futex_queue(q, hb); + futex_queue(q, hb, current); /* Arm the timer */ if (timeout) @@ -461,7 +461,7 @@ int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *woken) * next futex. Queue each futex at this moment so hb can * be unlocked. */ - futex_queue(q, hb); + futex_queue(q, hb, current); continue; } -- 2.39.5