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 96C96318EEE for ; Mon, 4 May 2026 08:52:18 +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=1777884738; cv=none; b=dro+D2tGPxs1BjBk2ykN2enrt8WH30LICXHbPY1KQyg9p4bp+MBltN+ohuQALSELRULRqsKGyQ5f766JfJJdW+c+XiYIpLdCgttwtHoHlI+SQYFP6CK/93rl256o99mxo9MwyeXEs5DBIE+cskH8JXSLI8d5YEoSlZqnDFGLUXc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777884738; c=relaxed/simple; bh=HuFfhsaWweKjECWKYLRNQkSRzxwk2hSr02HmoK/p2so=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=GzsPcrdmtCJnu2WIXmyy0ReXl9eybE9exL+ScX1sWWD8anruyEi8qkMLGxXaS/xxv+ezr13UO9L34Yb37fNwBMRm5CVFbH0M8unuvbyXh+QUkOXWSasNnCNYNHDxlGrtPMo6st8dDFhQ7YGZktnaSPramhcIjFsOl+ON/VygKfM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hBXob6Qm; 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="hBXob6Qm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2411FC2BCB8; Mon, 4 May 2026 08:52:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777884738; bh=HuFfhsaWweKjECWKYLRNQkSRzxwk2hSr02HmoK/p2so=; h=Subject:To:Cc:From:Date:From; b=hBXob6Qm34HkfukABF3wu3lhHpx6ZTbFhUugtpBXLyUJYVXjZO+Fuoe9aa8HxDRUI PLfQ+xMhhwuCIIlUnf3mtbm4gSRO1OC3uRmtpa+JkQ5p7pQxYLACiAXddU82XOUp8L 1ex9V/9yPm1e9fPHB6aRa5yd9rZn1vB70MOGjY4Q= Subject: FAILED: patch "[PATCH] rtmutex: Use waiter::task instead of current in" failed to apply to 5.10-stable tree To: keenanat2000@gmail.com,bird@lzu.edu.cn,tglx@kernel.org,tomapufckgml@gmail.com,yifanwucs@gmail.com,yuantan098@gmail.com Cc: From: Date: Mon, 04 May 2026 10:52:16 +0200 Message-ID: <2026050416-constrain-galore-c174@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x 3bfdc63936dd4773109b7b8c280c0f3b5ae7d349 # git commit -s git send-email --to '' --in-reply-to '2026050416-constrain-galore-c174@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 3bfdc63936dd4773109b7b8c280c0f3b5ae7d349 Mon Sep 17 00:00:00 2001 From: Keenan Dong Date: Wed, 8 Apr 2026 16:46:00 +0800 Subject: [PATCH] rtmutex: Use waiter::task instead of current in remove_waiter() remove_waiter() is used by the slowlock paths, but it is also used for proxy-lock rollback in rt_mutex_start_proxy_lock() when invoked from futex_requeue(). In the latter case waiter::task is not current, but remove_waiter() operates on current for the dequeue operation. That results in several problems: 1) the rbtree dequeue happens without waiter::task::pi_lock being held 2) the waiter task's pi_blocked_on state is not cleared, which leaves a dangling pointer primed for UAF around. 3) rt_mutex_adjust_prio_chain() operates on the wrong top priority waiter task Use waiter::task instead of current in all related operations in remove_waiter() to cure those problems. [ tglx: Fixup rt_mutex_adjust_prio_chain(), add a comment and amend the changelog ] Fixes: 8161239a8bcc ("rtmutex: Simplify PI algorithm and make highest prio task get lock") Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Signed-off-by: Keenan Dong Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index ccaba6148b61..4f386ea6c792 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1544,6 +1544,8 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock, * * Must be called with lock->wait_lock held and interrupts disabled. It must * have just failed to try_to_take_rt_mutex(). + * + * When invoked from rt_mutex_start_proxy_lock() waiter::task != current ! */ static void __sched remove_waiter(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter) @@ -1551,14 +1553,15 @@ static void __sched remove_waiter(struct rt_mutex_base *lock, { bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); struct task_struct *owner = rt_mutex_owner(lock); + struct task_struct *waiter_task = waiter->task; struct rt_mutex_base *next_lock; lockdep_assert_held(&lock->wait_lock); - raw_spin_lock(¤t->pi_lock); - rt_mutex_dequeue(lock, waiter); - current->pi_blocked_on = NULL; - raw_spin_unlock(¤t->pi_lock); + scoped_guard(raw_spinlock, &waiter_task->pi_lock) { + rt_mutex_dequeue(lock, waiter); + waiter_task->pi_blocked_on = NULL; + } /* * Only update priority if the waiter was the highest priority @@ -1594,7 +1597,7 @@ static void __sched remove_waiter(struct rt_mutex_base *lock, raw_spin_unlock_irq(&lock->wait_lock); rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, - next_lock, NULL, current); + next_lock, NULL, waiter_task); raw_spin_lock_irq(&lock->wait_lock); }