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 B6FD52DCF70 for ; Thu, 20 Nov 2025 19:38:27 +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=1763667507; cv=none; b=aNPHBnynzHzNZvz3tVvfeLgYn8HX9CDbhmga9AsRdKgE73K+qAqkjaXfihVrJjf3ggi1QRTvfd+km8duTU/gz1WM1tID39ZA5hRB0r2PUo87dMtND1k+UXNb5UCzA6LMQidqShQyzGsu6B1rGg1oIk+VkPVP99TNdDGxCsWHXIk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763667507; c=relaxed/simple; bh=fBLTANODSfkqSh8+8qVVdC4+k64zS+gYxxbuXJMJzJw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TviGlOIQgn+2QS17xa1QOOEZP74NINpoAXFSuN10BIHgZTbW/U7uw89fUZERQYu23ti9flF1Yj0wh0mP0n5tXng/3MYkM4a2xYq3rva2sTg/DXFN4dYaYzaU1mSXZ1uOxZ9QxQugy1RRcXoImJ2pVb5Jy1A6beF2yO75fMDlGOo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AZaULMBK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AZaULMBK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F14ADC4CEF1; Thu, 20 Nov 2025 19:38:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763667507; bh=fBLTANODSfkqSh8+8qVVdC4+k64zS+gYxxbuXJMJzJw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AZaULMBKCEVt5hWh2Vx9vY0DnEUdCyfnW1U6dU542V4uaK2MsWtLx781NSZ1Y+EK3 cuxxGnNNDzXB8HN6oIexj3CMYsjgUeIfjKI5SP82bu7fPjA9lKVrdP7phNFFMMxhHO kVApgz8Bca5hVFNFpK6d9cjxSb+BXAhH0jc/ofth82u9xZ9RdBFMiOKwDCrSLNy6b9 2RRypWPoz+J6KxmVgKSOHz0vRYoYu87I8zOV7Reqkk4lhSTdHFCP6UiQG8O+D6N372 iigNVscMBmyC+qP5WYnnUDWUl7oWvHLfZjOJznowZb1qymSeunyQsfC8e2+5HISQ5+ Z4HiA9bSR8oPg== From: Mike Rapoport To: stable@vger.kernel.org Cc: Mike Rapoport , Lance Yang , Google Big Sleep , David Hildenbrand , Lorenzo Stoakes , "Matthew Wilcox (Oracle)" , Andrew Morton Subject: [PATCH 5.15.y] mm/secretmem: fix use-after-free race in fault handler Date: Thu, 20 Nov 2025 21:38:21 +0200 Message-ID: <20251120193821.2353216-1-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <2025112023-overact-rehydrate-ae42@gregkh> References: <2025112023-overact-rehydrate-ae42@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Lance Yang When a page fault occurs in a secret memory file created with `memfd_secret(2)`, the kernel will allocate a new page 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 page and removing the page from the direct map, but only one would succeed in adding the page to the file mapping. The task that failed undoes the effects of its attempt by (a) freeing the page 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 page 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 (cherry picked from commit 6f86d0534fddfbd08687fa0f01479d4226bc3c3d) [rppt: replaced folio with page in the patch and in the changelog] Signed-off-by: Mike Rapoport (Microsoft) --- mm/secretmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/secretmem.c b/mm/secretmem.c index 624663a94808..0c86133ad33f 100644 --- a/mm/secretmem.c +++ b/mm/secretmem.c @@ -82,13 +82,13 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf) __SetPageUptodate(page); err = add_to_page_cache_lru(page, mapping, offset, gfp); if (unlikely(err)) { - put_page(page); /* * 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(page); + put_page(page); if (err == -EEXIST) goto retry; -- 2.50.1