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 158923043DD; Tue, 30 Sep 2025 15:29:53 +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=1759246194; cv=none; b=GvLYLo1KWeeJ4aQv648YUc3/FJZWVt0pP+XpMTe8lbKNXyWJSFvqkz1IXD4Zv23BHpPR+3BJ7sR6ezTyz4fDJsqEhulINUXkBE9CASVH3ojHR7eTgMJgxU4qeielyfcVjeEftVJwLeiyFtdZMAUL22cbq741liLU7u+/8RiIbY0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759246194; c=relaxed/simple; bh=ThXWgm0oz4wxkOI/7aH9icv2d2wjXCRdHy+7iUQoN1M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=hyvckxkJIDmqayJqFAkuB9c3VA8mxyNKrbyBbQ+El0cGoSS8bvpq9jwxolc/XhP62C3UD6qQH665/pzNCG2g09uAVXjfJcki0j44TXlJ03U7c8wwK4TmVrBlLiGf2MaDjwejDDh7wvUPOkKSegkkhY/YXHgtDox8xHb8DzYnTJk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xJrFpN8a; 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="xJrFpN8a" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F73AC4CEF0; Tue, 30 Sep 2025 15:29:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759246193; bh=ThXWgm0oz4wxkOI/7aH9icv2d2wjXCRdHy+7iUQoN1M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xJrFpN8aWvZdQWNIvCO16Q4z8Cv5zJhMZmUjPti6Clfo3a2FE6U0hk8IF+oi9uzt8 NbApEgZrZE+TI/AcKuuJ8uLvUB01UC1yNpDQxUQRqPOnE0dXYp5NbJRFAEEjhtdv+4 hS7lAy0eXVBah4e32tu5XTJsEVHBWeRbtGL5hT5k= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jakub Acs , Muhammad Usama Anjum , David Hildenbrand , Vlastimil Babka , Lorenzo Stoakes , Jinjiang Tu , Suren Baghdasaryan , Penglei Jiang , Mark Brown , Baolin Wang , Ryan Roberts , Andrei Vagin , =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= , Stephen Rothwell , Andrew Morton Subject: [PATCH 6.12 82/89] fs/proc/task_mmu: check p->vec_buf for NULL Date: Tue, 30 Sep 2025 16:48:36 +0200 Message-ID: <20250930143825.288941793@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250930143821.852512002@linuxfoundation.org> References: <20250930143821.852512002@linuxfoundation.org> User-Agent: quilt/0.69 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jakub Acs commit 28aa29986dde79e8466bc87569141291053833f5 upstream. When the PAGEMAP_SCAN ioctl is invoked with vec_len = 0 reaches pagemap_scan_backout_range(), kernel panics with null-ptr-deref: [ 44.936808] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 44.937797] KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] [ 44.938391] CPU: 1 UID: 0 PID: 2480 Comm: reproducer Not tainted 6.17.0-rc6 #22 PREEMPT(none) [ 44.939062] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 44.939935] RIP: 0010:pagemap_scan_thp_entry.isra.0+0x741/0xa80 [ 44.946828] Call Trace: [ 44.947030] [ 44.949219] pagemap_scan_pmd_entry+0xec/0xfa0 [ 44.952593] walk_pmd_range.isra.0+0x302/0x910 [ 44.954069] walk_pud_range.isra.0+0x419/0x790 [ 44.954427] walk_p4d_range+0x41e/0x620 [ 44.954743] walk_pgd_range+0x31e/0x630 [ 44.955057] __walk_page_range+0x160/0x670 [ 44.956883] walk_page_range_mm+0x408/0x980 [ 44.958677] walk_page_range+0x66/0x90 [ 44.958984] do_pagemap_scan+0x28d/0x9c0 [ 44.961833] do_pagemap_cmd+0x59/0x80 [ 44.962484] __x64_sys_ioctl+0x18d/0x210 [ 44.962804] do_syscall_64+0x5b/0x290 [ 44.963111] entry_SYSCALL_64_after_hwframe+0x76/0x7e vec_len = 0 in pagemap_scan_init_bounce_buffer() means no buffers are allocated and p->vec_buf remains set to NULL. This breaks an assumption made later in pagemap_scan_backout_range(), that page_region is always allocated for p->vec_buf_index. Fix it by explicitly checking p->vec_buf for NULL before dereferencing. Other sites that might run into same deref-issue are already (directly or transitively) protected by checking p->vec_buf. Note: >>From PAGEMAP_SCAN man page, it seems vec_len = 0 is valid when no output is requested and it's only the side effects caller is interested in, hence it passes check in pagemap_scan_get_args(). This issue was found by syzkaller. Link: https://lkml.kernel.org/r/20250922082206.6889-1-acsjakub@amazon.de Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs") Signed-off-by: Jakub Acs Reviewed-by: Muhammad Usama Anjum Acked-by: David Hildenbrand Cc: Vlastimil Babka Cc: Lorenzo Stoakes Cc: Jinjiang Tu Cc: Suren Baghdasaryan Cc: Penglei Jiang Cc: Mark Brown Cc: Baolin Wang Cc: Ryan Roberts Cc: Andrei Vagin Cc: "Michał Mirosław" Cc: Stephen Rothwell Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- fs/proc/task_mmu.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -2259,6 +2259,9 @@ static void pagemap_scan_backout_range(s { struct page_region *cur_buf = &p->vec_buf[p->vec_buf_index]; + if (!p->vec_buf) + return; + if (cur_buf->start != addr) cur_buf->end = addr; else