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 E5E3EDF6D; Sat, 13 Jan 2024 09:56:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="I3FTkNUN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 23866C43390; Sat, 13 Jan 2024 09:56:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1705139768; bh=vz3lTZD5j0hnadsF5MUiTzRU5xO1DGcmd5AIUPTKa7E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=I3FTkNUN1nUci7ASzOtgm4RhDdUWnpP+D2bPRcK5EbZGSjqllv9ovIMwrzbrTaY4b nyC0FvpM/gLYjsWuhk+NNchbV5VtRoRYW0f1NcWW9aZwAI8YubnkGZaFDzrN3Rrxjv 5+Iq+0O6q99T6o1xS073Fy1bD9/XJZxvQEjFBNko= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jiajun Xie , Andrew Morton Subject: [PATCH 5.4 24/38] mm: fix unmap_mapping_range high bits shift bug Date: Sat, 13 Jan 2024 10:50:00 +0100 Message-ID: <20240113094207.187633705@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240113094206.455533180@linuxfoundation.org> References: <20240113094206.455533180@linuxfoundation.org> User-Agent: quilt/0.67 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 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiajun Xie commit 9eab0421fa94a3dde0d1f7e36ab3294fc306c99d upstream. The bug happens when highest bit of holebegin is 1, suppose holebegin is 0x8000000111111000, after shift, hba would be 0xfff8000000111111, then vma_interval_tree_foreach would look it up fail or leads to the wrong result. error call seq e.g.: - mmap(..., offset=0x8000000111111000) |- syscall(mmap, ... unsigned long, off): |- ksys_mmap_pgoff( ... , off >> PAGE_SHIFT); here pgoff is correctly shifted to 0x8000000111111, but pass 0x8000000111111000 as holebegin to unmap would then cause terrible result, as shown below: - unmap_mapping_range(..., loff_t const holebegin) |- pgoff_t hba = holebegin >> PAGE_SHIFT; /* hba = 0xfff8000000111111 unexpectedly */ The issue happens in Heterogeneous computing, where the device(e.g. gpu) and host share the same virtual address space. A simple workflow pattern which hit the issue is: /* host */ 1. userspace first mmap a file backed VA range with specified offset. e.g. (offset=0x800..., mmap return: va_a) 2. write some data to the corresponding sys page e.g. (va_a = 0xAABB) /* device */ 3. gpu workload touches VA, triggers gpu fault and notify the host. /* host */ 4. reviced gpu fault notification, then it will: 4.1 unmap host pages and also takes care of cpu tlb (use unmap_mapping_range with offset=0x800...) 4.2 migrate sys page to device 4.3 setup device page table and resolve device fault. /* device */ 5. gpu workload continued, it accessed va_a and got 0xAABB. 6. gpu workload continued, it wrote 0xBBCC to va_a. /* host */ 7. userspace access va_a, as expected, it will: 7.1 trigger cpu vm fault. 7.2 driver handling fault to migrate gpu local page to host. 8. userspace then could correctly get 0xBBCC from va_a 9. done But in step 4.1, if we hit the bug this patch mentioned, then userspace would never trigger cpu fault, and still get the old value: 0xAABB. Making holebegin unsigned first fixes the bug. Link: https://lkml.kernel.org/r/20231220052839.26970-1-jiajun.xie.sh@gmail.com Signed-off-by: Jiajun Xie Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/memory.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/memory.c +++ b/mm/memory.c @@ -2872,8 +2872,8 @@ void unmap_mapping_pages(struct address_ void unmap_mapping_range(struct address_space *mapping, loff_t const holebegin, loff_t const holelen, int even_cows) { - pgoff_t hba = holebegin >> PAGE_SHIFT; - pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT; + pgoff_t hba = (pgoff_t)(holebegin) >> PAGE_SHIFT; + pgoff_t hlen = ((pgoff_t)(holelen) + PAGE_SIZE - 1) >> PAGE_SHIFT; /* Check for overflow. */ if (sizeof(holelen) > sizeof(hlen)) {