From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70945C4167B for ; Wed, 9 Dec 2020 18:14:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E78323C1A for ; Wed, 9 Dec 2020 18:14:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732740AbgLISOM (ORCPT ); Wed, 9 Dec 2020 13:14:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42932 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732438AbgLISOM (ORCPT ); Wed, 9 Dec 2020 13:14:12 -0500 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C6A9C0613CF for ; Wed, 9 Dec 2020 10:13:32 -0800 (PST) Received: by mail-pj1-x1042.google.com with SMTP id p21so1026134pjv.0 for ; Wed, 09 Dec 2020 10:13:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=BPpiVwJwbCA/SJkH1A30g3V3EvTXlK0B5wY4Rt0mSqQ=; b=Zev595F216Rc3TBUQGuC7gFiQSKi3xmHZh9VbmYr2J0aZ/2J4H0gNmA8rAoP2iJxzw XQ01BR8WSQPUviY2uVghZHY9gDSWP4KGi2xuAkF+QfYdzx8EPAUSIXFZYG+p/KsREBql KuSlbePTtq1SyObqovFY8f6hdx2QKVK4ZLD0YMotel1p/8OBlAg4nm7rzar9GAKcATnU 4PjK6uNuC8rYwtxW6ICdinsGM39GvkgviGaovxs5BShJsXa3SFqh4Z4MCZXPYBAI4mK9 Qj1DxRlkSnGKf7v179o+nfd9tOmE5D7lf8LitLofCqkruylF/PsLMJr/TEdiwOHvRzsA UYCQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=BPpiVwJwbCA/SJkH1A30g3V3EvTXlK0B5wY4Rt0mSqQ=; b=TbDdIX7Ar0CTlrgBpMBDdb/KEmMrVphknYkFP1GOLjB0XQI0C5Hv5qP8qMtg2w9ev8 iBs/5g0Zk0SZDSwcGJrVXpx1x99fisXOu9h2I8HvXaoY8Jy0sb35s/RzYU5zTlrsjC+j RRyxltRdgKcdqFHXa0aYuxRa9pt7ffWssF+VL30SFp2VfGocw2TG15PUwle9FJDGqowD IpT3bWrKYGRkCHX/tWd+vQEZbagjOoSFfdEWOdPSPPY1NfMIA9S3LPX94chD5ERKAYLz 9faZVh7oR0uRrdNqcjeT4V5aY8DsOQlI2gX7CBHnaewW+bSBDC7jBLI3DvtejQTfNJ6V UZrw== X-Gm-Message-State: AOAM532iM8Qbkrr1pnGD5JQrrblBeEBTNqhv0Cgx5E0qwTDycdl94Lr3 s9mJOQQCH6SmVCQ30vcrUTM= X-Google-Smtp-Source: ABdhPJz+LnsD+M/2QOtOCDI6Djqe7Vn94N8UA5khAEi/S9ljjHipC9M2D+eY2yr4Pj2X1gTSa4KG3g== X-Received: by 2002:a17:902:63:b029:db:c0d6:96ec with SMTP id 90-20020a1709020063b02900dbc0d696ecmr3262997pla.13.1607537610507; Wed, 09 Dec 2020 10:13:30 -0800 (PST) Received: from localhost.localdomain ([49.207.201.111]) by smtp.gmail.com with ESMTPSA id p21sm3078636pfn.15.2020.12.09.10.13.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Dec 2020 10:13:29 -0800 (PST) From: Anant Thazhemadam To: Jaegeuk Kim , Chao Yu Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Anant Thazhemadam , syzbot+ca9a785f8ac472085994@syzkaller.appspotmail.com Subject: [PATCH] fs: f2fs: fix potential shift-out-of-bounds error in sanity_check_raw_super() Date: Wed, 9 Dec 2020 23:43:22 +0530 Message-Id: <20201209181322.27932-1-anant.thazhemadam@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In sanity_check_raw_super(), if 1 << le32_to_cpu(raw_super->log_blocksize) != F2FS_BLKSIZE, then the block size is deemed to be invalid. syzbot triggered a shift-out-of-bounds bug by assigning a value of 59 to le32_to_cpu(raw_super->log_blocksize). Although the value assigned itself isn't of much significance, this goes to show that even if the block size is invalid, le32_to_cpu(raw_super->log_blocksize) can be potentially evaluated to a value for which the shift exponent becomes too large for the unsigned int. Since 1 << le32_to_cpu(raw_super->log_blocksize) must be = 4096 for a valid block size, le32_to_cpu(raw_super->log_blocksize) must equal 12. Replacing the existing check with the more direct sanity check resolves this bug. Reported-by: syzbot+ca9a785f8ac472085994@syzkaller.appspotmail.com Tested-by: syzbot+ca9a785f8ac472085994@syzkaller.appspotmail.com Signed-off-by: Anant Thazhemadam --- fs/f2fs/super.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 33808c397580..4bc7372af43f 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -2775,7 +2775,6 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi, block_t total_sections, blocks_per_seg; struct f2fs_super_block *raw_super = (struct f2fs_super_block *) (bh->b_data + F2FS_SUPER_OFFSET); - unsigned int blocksize; size_t crc_offset = 0; __u32 crc = 0; @@ -2802,10 +2801,8 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi, } /* Currently, support only 4KB block size */ - blocksize = 1 << le32_to_cpu(raw_super->log_blocksize); - if (blocksize != F2FS_BLKSIZE) { - f2fs_info(sbi, "Invalid blocksize (%u), supports only 4KB", - blocksize); + if (le32_to_cpu(raw_super->log_blocksize) != 12) { + f2fs_info(sbi, "Invalid blocksize. Only 4KB supported"); return -EFSCORRUPTED; } -- 2.25.1