From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f173.google.com (mail-dy1-f173.google.com [74.125.82.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 92C9944BCBE for ; Tue, 13 Oct 2026 02:09:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791857388; cv=none; b=KbRTsUAvsONkVpRS0Zctye2LCjsfj7UW/hwS54GUaToz8wCysQhwnwEDBvnMKYK5bo9QQC8ZYCE2j0q39XAHB5y/I06ozkmMvuvgavgCOo6B0ix7HBR/naTs29eJ3exrcSQFXVhC2XgsBSD1e6sJwe5ROenGl0M5XUX+Der/JAA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791857388; c=relaxed/simple; bh=czPVgNXT2OgaXwjFbvuyK45RKjR2md9vJ04hkTHTkCE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=SuiEgcTfKA87TG7TuMH9eG8GsZrie9gSSVsp1qFkbyOq4/iKMoj+zNwELvpwKqtPok1Qkn35See3l5Ng3Jxv74Jgu8YI60j6cyH/3R+bx8azf8oxgQh5wvjREEncmvq/FThmcVTt8T4PSAPHQ2/1yD2LBcPs741fwC97NILw0Pg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=gnFCcreV; arc=none smtp.client-ip=74.125.82.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gnFCcreV" Received: by mail-dy1-f173.google.com with SMTP id 5a478bee46e88-353804b591eso4165617eec.0 for ; Mon, 12 Oct 2026 19:09:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1791857387; x=1792462187; darn=vger.kernel.org; h=cc:to:message-id:content-transfer-encoding:content-type :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to:content-type; bh=53/8rFLtj+oKerssY2sv6i0RQan/DUVl/IJk1Ms9Yfc=; b=gnFCcreV0QYBNJTRlHo8PHFszPMpk3CNNVt3DdgKNnhWEZQ1V27Tv1axmCcyRTzkcR yZVnB+0gWVjzBbDS0QLMynvvSxIn8PfLjmm0b1yzXWIlyZuBHeJsIQdhc658ueiy4Icr Guqxf/RMKFPo0dggDLfjmK3Djzo2T1zegE36F22nNRgFGAdgfH4Nzb+ixj9l/XabJbL1 5C3RLOOH/rDr9tEQYnHqxNu7zZUz4d54nIOtzkfraAkSlliIdi1DpB81UXYLdsHtzrMR AJ3PD+2XLs2UcAP8VxIcYpovPv5afhuHCArV5nthwW2kCcqGSScU8mZJvRPYLuurEwH8 WUHA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791857387; x=1792462187; h=cc:to:message-id:content-transfer-encoding:content-type :mime-version:subject:date:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to:content-type; bh=53/8rFLtj+oKerssY2sv6i0RQan/DUVl/IJk1Ms9Yfc=; b=N3EU1dMp3/wYYicKfFLgfsuy3qddq6iehRnX1jFR8v/XC96wwLqoppSs1v/y1oyJcv 4uQ8sPrExvLTvjVCiMDg5HMZtx3N3eSyKwBpWyLvFiET6Of0HieBx+J+sFeken16TaGT qgz0t8xJIOKQ//eUQQyL76Qyl5b7hVTmQ8LQDI9RMoS6n0QDncjxTaRW53P2sDGkmEbW tOMbi8PIKLAS9ZyfI13/Q2ZQPwzmcxH29AIEp/TA92sjObenTExd162SBqE7gnqbpEIZ 97WVKOOwwsYoTcC2lmPveMLW+MEkRTczGv4ZXtOMIo+g8WOpVsuJhg24YKuxcosRdXHD VWqA== X-Forwarded-Encrypted: i=1; AKwUvByV8M1HP8HTkwPcPhxSf9SCOsmvin0ClFgmCuJXtkLxdQbcRPLCBGGwU5m6Y6tV65pEUNMxxZcWWxYxMTI=@vger.kernel.org X-Gm-Message-State: AFq9FYIip/SuhIHk1/TRsBwL388glcqYVqvJ7cNbgYQqYPeEC6qG+Ilz UdeQAQyAeovI7BtnbdMKwxusFA1A/v3mbjkrxpcsEP3rcrEIlc+resLv X-Gm-Gg: AYBFou3qeffS3KMY8mRah4o8d/3pAA5Vrk4lGPg6b3KR06LJTKAjHVqQKNAdqpMVPk0 D5XBXHuTGacBsNIsrauT2UiO/KcybND3X+OHFI8kq0QVw+JecM96u3eJmkzBeLvpSTfacBefIB1 dqijOeTUWl25BFtb/DxaFGaDoLeQIDpsMxpjsrafLm9pQ3vp+1zuxUA3igvhwC3NfR8MFoiFuRn 3NcF6EkLbcX59GZho6wb1bf3EP+7aosl2Y/X8ACSgdFuUdvGelCsCmQ1r1iTSZlNjif2OUnPu3o z7XqUo2Bl4X9jmj3aRIxrTQkcJdgL7PdU6vZALU2xwhGTBmq+PXkDafgMgq8jnK0oDjvJzkAbcK 38WouJsMRUsn+AaHqnyYWJUBOVacMf0MuQohrPNcyN1KlW9mesePBYGLO4U1Mw8/6CW3vmddFnd +kOKgjzZKBom2mpp7AST/y3RmILgIRpKUHx/Dao5rcGuB+qawuS5HMnZQS62Om06BvsAC2kkRxx lRj/LwlDm5s X-Received: by 2002:a05:7300:d103:b0:35b:3181:80e9 with SMTP id 5a478bee46e88-35b31818605mr4170366eec.20.1791857386463; Mon, 12 Oct 2026 19:09:46 -0700 (PDT) Received: from [127.0.1.1] ([2404:f801:8028:3:8056:897e:dae3:8e2e]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-35b19c6c7b4sm11643813eec.24.2026.10.12.19.09.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Oct 2026 19:09:46 -0700 (PDT) From: Subasri S Date: Tue, 13 Oct 2026 07:39:40 +0530 Subject: [PATCH RESEND] bcache: validate sb->keys before computing checksum Precedence: bulk X-Mailing-List: linux-bcache@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261013-bcache-super-v1-1-7bf7e6930eac@gmail.com> To: Coly Li , Kent Overstreet Cc: Kent Overstreet , linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+cb5b32abe226710cdd8a@syzkaller.appspotmail.com, Subasri S X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1791857383; l=2095; i=subasris1210@gmail.com; s=20260709; h=from:subject:message-id; bh=czPVgNXT2OgaXwjFbvuyK45RKjR2md9vJ04hkTHTkCE=; b=q+gXKToLe6oG7kwfZ0k9csc6qr5Y9W9z3QyJnSfj4hKUWIUfXYAE3pyWQL+OrlvARUkKCeDOC DjRaNK5jm19AD6Nn4FJuz51T7Tev3PCB3RjEinD0Pg2ltQR0O4kTOCl X-Developer-Key: i=subasris1210@gmail.com; a=ed25519; pk=6C4wavGFy/OsR8yQQKNWuDXoYPHp2L3sfgNfyzTruTk= csum_set() checksums the superblock from just past the csum field up to &s->d[s->keys], so the length it hands to bch_crc64() comes straight off disk. d[] only has SB_JOURNAL_BUCKETS (256) entries, but keys is __le16 and can be up to 65535, so a bogus value makes the crc walk far past the end of the 4k superblock buffer. syzbot hit this with a superblock that has a valid offset and magic and garbage everywhere else: BUG: KASAN: use-after-free in crc64_be_generic lib/crc/crc64-main.c:47 [inline] BUG: KASAN: use-after-free in crc64_be+0xb8/0xe8 lib/crc/crc64-main.c:68 Read of size 1 at addr ffff0000dd543000 by task syz.0.33/4986 Call trace: kasan_report+0x8c/0xc4 mm/kasan/report.c:595 __asan_report_load1_noabort+0x20/0x2c mm/kasan/report_generic.c:378 crc64_be_generic lib/crc/crc64-main.c:47 [inline] crc64_be+0xb8/0xe8 lib/crc/crc64-main.c:68 bch_crc64 drivers/md/bcache/util.h:529 [inline] read_super drivers/md/bcache/super.c:208 [inline] Add a bound check on sb->keys before calculating checksum. Reported-by: syzbot+cb5b32abe226710cdd8a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=cb5b32abe226710cdd8a Tested-by: syzbot+cb5b32abe226710cdd8a@syzkaller.appspotmail.com Fixes: cafe56359144 ("bcache: A block layer cache") Signed-off-by: Subasri S --- drivers/md/bcache/super.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 97d9adb0bf96b..71929576ab89e 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -204,6 +204,10 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev, if (memcmp(sb->magic, bcache_magic, 16)) goto err; + err = "Too many journal buckets"; + if (sb->keys > SB_JOURNAL_BUCKETS) + goto err; + err = "Bad checksum"; if (s->csum != csum_set(s)) goto err; --- base-commit: 15ef2f78c49d20d53ec7c0f1c9b40b02e089f2d6 change-id: 20260815-bcache-super-5e48eebfc4ad Best regards, -- Subasri S