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 0A1D71DB147; Wed, 15 Jan 2025 10:46:15 +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=1736937975; cv=none; b=Aahe7zDabHGbOq6yc+CmMLeeO/RvsQPqpl3XB3OivyqrFnWDW/P1w6mjboWxi00iC7q1skGXPaHL9Dtc+bJyqT5yKxAVzQLWLnVJd4iHe5Ct1iWSVL9IUKosoDpbLSRclpCZZ2HqBNAiJke46fGoYwxUgZHZA/DKqOagh21/f0w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736937975; c=relaxed/simple; bh=ccCZvnP0Izl+UJlrpMoqDlT1Bb2Z3r6kYYqpyRLLCdY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pBeMxPJ79TsCd3D+Hklia1Djz7KafVhusp0MMfqRwj6AKNGTRcC48asL1cHQZ97jbDHYbtMhTjpNSAHyctUSEHXobZ3DWXlfKsla/Hv79MR8QMlCAcmqA2cJPmQyCageMvO5fpwuFQKZ/zVOXUw5Zngovppy2mPcWoJrW+jfJXc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=noVgbti+; 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="noVgbti+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3DDFCC4CEDF; Wed, 15 Jan 2025 10:46:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1736937974; bh=ccCZvnP0Izl+UJlrpMoqDlT1Bb2Z3r6kYYqpyRLLCdY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=noVgbti+59k6bNxPXDjE8UnLgacVq+zWGSqdj/JKKyoS6pJfPpdS+bL++ameGiIhu 0tbA0SdkFyGRPTqrFWzQ77jOpFMloduWsBmTr9akk2xAdO2HVdSxTHucWAr7YtS0Q8 l11zGlSDoBPM7rpmadgU9U+m6Uf+Kgxf87dJIsL8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+339e9dbe3a2ca419b85d@syzkaller.appspotmail.com, Anand Jain , Qu Wenruo , David Sterba , Sasha Levin Subject: [PATCH 6.12 029/189] btrfs: avoid NULL pointer dereference if no valid extent tree Date: Wed, 15 Jan 2025 11:35:25 +0100 Message-ID: <20250115103607.521732986@linuxfoundation.org> X-Mailer: git-send-email 2.48.0 In-Reply-To: <20250115103606.357764746@linuxfoundation.org> References: <20250115103606.357764746@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Qu Wenruo [ Upstream commit 6aecd91a5c5b68939cf4169e32bc49f3cd2dd329 ] [BUG] Syzbot reported a crash with the following call trace: BTRFS info (device loop0): scrub: started on devid 1 BUG: kernel NULL pointer dereference, address: 0000000000000208 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 106e70067 P4D 106e70067 PUD 107143067 PMD 0 Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 1 UID: 0 PID: 689 Comm: repro Kdump: loaded Tainted: G O 6.13.0-rc4-custom+ #206 Tainted: [O]=OOT_MODULE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022 RIP: 0010:find_first_extent_item+0x26/0x1f0 [btrfs] Call Trace: scrub_find_fill_first_stripe+0x13d/0x3b0 [btrfs] scrub_simple_mirror+0x175/0x260 [btrfs] scrub_stripe+0x5d4/0x6c0 [btrfs] scrub_chunk+0xbb/0x170 [btrfs] scrub_enumerate_chunks+0x2f4/0x5f0 [btrfs] btrfs_scrub_dev+0x240/0x600 [btrfs] btrfs_ioctl+0x1dc8/0x2fa0 [btrfs] ? do_sys_openat2+0xa5/0xf0 __x64_sys_ioctl+0x97/0xc0 do_syscall_64+0x4f/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e [CAUSE] The reproducer is using a corrupted image where extent tree root is corrupted, thus forcing to use "rescue=all,ro" mount option to mount the image. Then it triggered a scrub, but since scrub relies on extent tree to find where the data/metadata extents are, scrub_find_fill_first_stripe() relies on an non-empty extent root. But unfortunately scrub_find_fill_first_stripe() doesn't really expect an NULL pointer for extent root, it use extent_root to grab fs_info and triggered a NULL pointer dereference. [FIX] Add an extra check for a valid extent root at the beginning of scrub_find_fill_first_stripe(). The new error path is introduced by 42437a6386ff ("btrfs: introduce mount option rescue=ignorebadroots"), but that's pretty old, and later commit b979547513ff ("btrfs: scrub: introduce helper to find and fill sector info for a scrub_stripe") changed how we do scrub. So for kernels older than 6.6, the fix will need manual backport. Reported-by: syzbot+339e9dbe3a2ca419b85d@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/67756935.050a0220.25abdd.0a12.GAE@google.com/ Fixes: 42437a6386ff ("btrfs: introduce mount option rescue=ignorebadroots") Reviewed-by: Anand Jain Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/scrub.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c index 3a3427428074..c73a41b1ad56 100644 --- a/fs/btrfs/scrub.c +++ b/fs/btrfs/scrub.c @@ -1541,6 +1541,10 @@ static int scrub_find_fill_first_stripe(struct btrfs_block_group *bg, u64 extent_gen; int ret; + if (unlikely(!extent_root)) { + btrfs_err(fs_info, "no valid extent root for scrub"); + return -EUCLEAN; + } memset(stripe->sectors, 0, sizeof(struct scrub_sector_verification) * stripe->nr_sectors); scrub_stripe_reset_bitmaps(stripe); -- 2.39.5