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 CD13538C427 for ; Fri, 13 Mar 2026 12:44:27 +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=1773405867; cv=none; b=PP278LOn0xNQEy3+LT5dGqv0CNBajby5p1Duhx+lbvMGbYfMplfO3xZDf5px/DVfSjRACMmhEdM/90w28d6WFDQHiQ/GMn+egut8QW+Se+FjIZFbCUBoqgaTMzq77+jf7JR3quOcYJ9fE6toxU8AnGq4D1nROXqBmFQXh6VpsHo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773405867; c=relaxed/simple; bh=4igv/njyyDqCBiOI9NwnVPBjGSrhcSKt6lOn2kp7p74=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XjpSBnnpaIU+vzgftz4ld8SyqWykEGx3YIYEwY3AHfgKMGsl36bm+Dz8fw2KsN4LYKp1wzrLlGDX2E4rhvOfM7lB719/iku/Ir5xonHXekzUp0oroHPBvWzta6WmU+Wjvsli0ZGc8ai94Mf113IkJZK0i1tU0HXc+4Euz9WFFcs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Xo2gr9Kb; 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="Xo2gr9Kb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCC76C19421; Fri, 13 Mar 2026 12:44:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1773405867; bh=4igv/njyyDqCBiOI9NwnVPBjGSrhcSKt6lOn2kp7p74=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Xo2gr9KbfmoI7Tgij6cQksILW/GDMLaMDPZtm1PlS9L70StRdBoWhLGQ7vyenC2JK Zsf9GndEWaYqB8Td9VZQyhObOsJJu9M3279AiiHgQ/qyoWq34vBjZlz8Be5pdq7F1y DqNdnb/Cy+F7v/mSMnHyVzsxS+icoi8mHWEZmTDA= Date: Fri, 13 Mar 2026 13:44:23 +0100 From: Greg KH To: Hao-Yu Yang Cc: security@kernel.org, tglx@kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] futex: Use-after-free between futex_key_to_node_opt and vma_replace_policy Message-ID: <2026031349-aging-colonize-39a0@gregkh> References: <20260313123940.51301-1-naup96721@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260313123940.51301-1-naup96721@gmail.com> On Fri, Mar 13, 2026 at 08:39:40PM +0800, Hao-Yu Yang wrote: > During futex_key_to_node_opt() execution, vma->vm_policy is read under > speculative mmap lock and RCU. Concurrently, mbind() may call > vma_replace_policy() which frees the old mempolicy immediately via > kmem_cache_free(). > > This creates a race where __futex_key_to_node() dereferences a freed > mempolicy pointer, causing a use-after-free read of mpol->mode. As this is sent to lkml in public, no need to get security@k.o involved. > [ 151.412631] BUG: KASAN: slab-use-after-free in __futex_key_to_node (kernel/futex/core.c:349) > [ 151.414046] Read of size 2 at addr ffff888001c49634 by task e/87 > [ 151.414476] > [ 151.415431] CPU: 1 UID: 1000 PID: 87 Comm: e Not tainted 7.0.0-rc3-g0257f64bdac7 #1 PREEMPT(lazy) > [ 151.415758] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 > [ 151.415969] Call Trace: > [ 151.416059] > [ 151.416161] dump_stack_lvl (lib/dump_stack.c:123) > [ 151.416299] print_report (mm/kasan/report.c:379 mm/kasan/report.c:482) > [ 151.416359] ? __virt_addr_valid (./include/linux/mmzone.h:2046 ./include/linux/mmzone.h:2198 arch/x86/mm/physaddr.c:54) > [ 151.416412] ? __futex_key_to_node (kernel/futex/core.c:349) > [ 151.416517] ? kasan_complete_mode_report_info (mm/kasan/report_generic.c:182) > [ 151.416583] ? __futex_key_to_node (kernel/futex/core.c:349) > [ 151.416631] kasan_report (mm/kasan/report.c:597) > [ 151.416677] ? __futex_key_to_node (kernel/futex/core.c:349) > [ 151.416732] __asan_load2 (mm/kasan/generic.c:271) > [ 151.416777] __futex_key_to_node (kernel/futex/core.c:349) > [ 151.416822] get_futex_key (kernel/futex/core.c:374 kernel/futex/core.c:386 kernel/futex/core.c:593) > [ 151.416871] ? __pfx_get_futex_key (kernel/futex/core.c:550) > [ 151.416927] futex_wake (kernel/futex/waitwake.c:165) > [ 151.416976] ? __pfx_futex_wake (kernel/futex/waitwake.c:156) > [ 151.417022] ? __pfx___x64_sys_futex_wait (kernel/futex/syscalls.c:398) > [ 151.417081] __x64_sys_futex_wake (kernel/futex/syscalls.c:382 kernel/futex/syscalls.c:366 kernel/futex/syscalls.c:366) > [ 151.417129] x64_sys_call (arch/x86/entry/syscall_64.c:41) > [ 151.417236] do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) > [ 151.417342] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) > [ 151.418312] > > Fix by adding rcu to __mpol_put(). > > change-log: > v2-v1: add rcu to __mpol_put This goes below the --- line. > > Fixes: c042c505210d ("futex: Implement FUTEX2_MPOL") > Reported-by: Hao-Yu Yang > Signed-off-by: Hao-Yu Yang > --- No cc: stable? thanks, greg k-h