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 3D4F433BBB2 for ; Thu, 20 Nov 2025 16:11:29 +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=1763655090; cv=none; b=KyRM4EImF+icFMlK0FLfxf/sQmlcJbaVMH3fWgOOE+FcVx6SV/fHT8p6mqaTATyfXznGj5JVHglRcmIAc3ur9baT+7m2WyLmRBhbcwEaMx6eA4GXZzsNvLKmqlN5Ba78vLufDj2h+yApYqL7lbv5iaxlZ4r1ITf3gkVaoam5OPI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763655090; c=relaxed/simple; bh=osjCowjAMM7psSitQ1JPkB+NhuliJfF7jynP1FEK22I=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=vAjEHvYjqOZaTO9OTUeQ1QJ6SNEF9OY3a+YWt/7Nxd/DryCE0pjfIWhq6g5ZphTW7fCLzc/OSUuX7Y8SAUipkOKdLsOx0mooQL1MBKTPQAsC6HegmpaX0cyA2x6m17qAAeM7bOfzaBmIjxkRuCWTlGXbU8ic2pLMPyxxNI7UQFA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Iz9F7hES; 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="Iz9F7hES" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74E8DC4CEF1; Thu, 20 Nov 2025 16:11:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1763655089; bh=osjCowjAMM7psSitQ1JPkB+NhuliJfF7jynP1FEK22I=; h=Subject:To:Cc:From:Date:From; b=Iz9F7hESre3tSgf2zOdxyJh9m2CPApx4ik+GJEO8DBYPRPuvC3xbKwTpvQwYBw+rS AT80WM6WRCFdybGAjf6lyOLzf9Cgi2gnvlrplZ8awN0fo9U/KK3YhnHUj6myDECuXR 3R+EJNyNW7AkB26xMN/hjs66I1mNkSBB+s77tATk= Subject: FAILED: patch "[PATCH] mm/secretmem: fix use-after-free race in fault handler" failed to apply to 6.6-stable tree To: lance.yang@linux.dev,akpm@linux-foundation.org,big-sleep-vuln-reports@google.com,david@redhat.com,lorenzo.stoakes@oracle.com,rppt@kernel.org,stable@vger.kernel.org,willy@infradead.org Cc: From: Date: Thu, 20 Nov 2025 17:11:21 +0100 Message-ID: <2025112021-swept-idealness-9ecb@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 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x 6f86d0534fddfbd08687fa0f01479d4226bc3c3d # git commit -s git send-email --to '' --in-reply-to '2025112021-swept-idealness-9ecb@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 6f86d0534fddfbd08687fa0f01479d4226bc3c3d Mon Sep 17 00:00:00 2001 From: Lance Yang Date: Fri, 31 Oct 2025 20:09:55 +0800 Subject: [PATCH] mm/secretmem: fix use-after-free race in fault handler When a page fault occurs in a secret memory file created with `memfd_secret(2)`, the kernel will allocate a new folio for it, mark the underlying page as not-present in the direct map, and add it to the file mapping. If two tasks cause a fault in the same page concurrently, both could end up allocating a folio and removing the page from the direct map, but only one would succeed in adding the folio to the file mapping. The task that failed undoes the effects of its attempt by (a) freeing the folio again and (b) putting the page back into the direct map. However, by doing these two operations in this order, the page becomes available to the allocator again before it is placed back in the direct mapping. If another task attempts to allocate the page between (a) and (b), and the kernel tries to access it via the direct map, it would result in a supervisor not-present page fault. Fix the ordering to restore the direct map before the folio is freed. Link: https://lkml.kernel.org/r/20251031120955.92116-1-lance.yang@linux.dev Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas") Signed-off-by: Lance Yang Reported-by: Google Big Sleep Closes: https://lore.kernel.org/linux-mm/CAEXGt5QeDpiHTu3K9tvjUTPqo+d-=wuCNYPa+6sWKrdQJ-ATdg@mail.gmail.com/ Acked-by: David Hildenbrand Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Signed-off-by: Andrew Morton diff --git a/mm/secretmem.c b/mm/secretmem.c index 60137305bc20..b59350daffe3 100644 --- a/mm/secretmem.c +++ b/mm/secretmem.c @@ -82,13 +82,13 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf) __folio_mark_uptodate(folio); err = filemap_add_folio(mapping, folio, offset, gfp); if (unlikely(err)) { - folio_put(folio); /* * If a split of large page was required, it * already happened when we marked the page invalid * which guarantees that this call won't fail */ set_direct_map_default_noflush(folio_page(folio, 0)); + folio_put(folio); if (err == -EEXIST) goto retry;