From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f53.google.com (mail-ej1-f53.google.com [209.85.218.53]) (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 A34D82D6407 for ; Wed, 10 Jun 2026 21:30:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781127031; cv=none; b=PHbZGISQPRRpGe1X9i5oAIl0yQgZ9bapL0dXGnINWhDp6XsVbhj9jDF45/u8V35t+E2tbvb2uVxxDQQJNIbYJ/RhvbWK9hGOTJw/9hIE4UJr2XsSfn3yq+ftURduBB5j1FXtHhZndhjATPrtK6ZgCGxkpNx5+GVnxD0wNSp64Mw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781127031; c=relaxed/simple; bh=knFZQIU3RitInb6GHEsKGhfF0ndcAKfemmGtq8EWZ8k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZR+L7+UxPrayrLuPKDxkJDGFy5EhaJFFnd3+ThdmM/ZpFwEDcZcII0YA5FLJrvQ8qzaZAlOIqUdPVdy1t/MzkhwrYSKdPNI5G1+oB122OwWKq+YarDR52nu9lt+VwV4dGOcqGkw/X98D+SSAdgMzSznhyX0rhB89NSQ6GJxxhM4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=gGHbwuWk; arc=none smtp.client-ip=209.85.218.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="gGHbwuWk" Received: by mail-ej1-f53.google.com with SMTP id a640c23a62f3a-bebde89cfd3so932018366b.2 for ; Wed, 10 Jun 2026 14:30:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1781127028; x=1781731828; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to; bh=PK0T0u1AQ2vQ2ApnaoP1ADurHDOYM8RYl9Zgetnmqqg=; b=gGHbwuWkBDURmF2+ijSMmhkP8D0bPiB7h+M4iDLZpJ6icEUPF+NbDIUxnnYC4onONv nzKW2NL7GfkPTgYeu/ZJ/dHcPCUYGqmqt5wz0evVVV7d+Tlbt8zrCbeCDzsxEBntgVoF aXfkmKIXknGTkXd+NavmGOC/1VoRa6wEOnHvKlRVRWmxpvXKXILgNbw13t2eNgZ8lEO4 wciTJ1qqgdO/gwReAdpLpflr493GoRaIQxjo4GuzbA76gWRpyp0g1KKQ3be76GsFCDgS IO2b0z5dXSDYn+G4c+ClUvWCLZZd/kNAw96lV0JJJ4VJ9DA8gys19HCRdQheZoZeWeq0 AcaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781127028; x=1781731828; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=PK0T0u1AQ2vQ2ApnaoP1ADurHDOYM8RYl9Zgetnmqqg=; b=Dajojy71mnWfTnvE5rk4ksHgbxjT2SD0g1aZ9B6Vfs87Bv0echX3t76+xXXWXaJEwL GCVy92qcVTeG/bLZgGOSASXIYvThwre4hsKchE2MTC0ZFHYBUhTil9vDHDCd6C9Dq81t 4OhAcja1KrDcW2BkY2nO/UnvB43CnKCTExBCP9RwhiSqo8aG02EJqzZTUI2G0TJ9OsvL aJu3QEyGL/3+jtfnU3+XG/vaGIOReEAzO4p/CrfvNj4h4vekufSnaT5Mey1pVv7s/HuY axmatWuuGZASLYEz15gMLw2kq6Wh/WRYHisyRYX328uRbay0UaQqhottx8e9FjIAN/F+ gOTg== X-Forwarded-Encrypted: i=1; AFNElJ9fOLRXKamFsSU2gLLg00m/QvvFfAqK0sOyeocHa26C8hOQANsNlZY30o8Pt7ckJTQytYl+2TfFnze9esM=@vger.kernel.org X-Gm-Message-State: AOJu0YyKbgsTO1j8JXhO4mhErKZih5WU3XaHSdON6PX3Sur1Dfv4bs9H L0KbR0Lg5rqCA7ux5I9ybDmUq1noxMvhORt+RyzwuzLveJJ77mocvwYnPLxEkOmMV+o= X-Gm-Gg: Acq92OHJjodhTqO+mRW70/gW/lSG2EYrzsDXUKAfarZxAtub15ncN8YQAWcQWv3GF3G X1FFFSrtmIZtU/SI4HGjfKYpsAK0jqBT30W3BeUpawoUbDZGCPBtTZkRlBRe9SO5iKDcH+Lb09R hmkN/d7rpq3FF4NkWrnPcGvExVnHjmGk7UPETqb9f69zBduP1te6qV/00AbmEDAyPB4xJhZc6yO 8MWau2zjhjrC9nwsVuwl1eq/Rbq8a+ENfdia6QerMNbvhHfl1GNFCBn1lxThrK4XCAlkVjg4C4Y tFRBXpB5oDQnnXs85/U1EjFIya6T4zTFX+jCndA1ye32RNJXK/wCc/k/GAevVhR+HJWaFKKvDMX OnfnUyJkTLuWp1ZdJmqXeIjjZ5UrHPU0uRRoXNyxom+kvrKWhXqFlrXxWOBeQhFJo2yGtsJ8Qvz aSr4Aj6wpniRmYhXiP2Ww+diSvv2dQpI7zrskuRc5/pxB8m4ISpCreIbxqsVnWUPzRWoqfEaGAZ vYRp4fLc3YhEiBdlyefU35bgyJH3cPIeq1dGdStmPU73aatsSLYyenJ X-Received: by 2002:a17:907:761a:b0:be3:b3fb:e2 with SMTP id a640c23a62f3a-bf372349b33mr1015295566b.32.1781127027759; Wed, 10 Jun 2026 14:30:27 -0700 (PDT) Received: from ?IPV6:2403:580d:fda1:0:2bb5:f164:6e6a:38d8? (2403-580d-fda1-0-2bb5-f164-6e6a-38d8.ip6.aussiebb.net. [2403:580d:fda1:0:2bb5:f164:6e6a:38d8]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84282883647sm29927068b3a.36.2026.06.10.14.30.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Jun 2026 14:30:26 -0700 (PDT) Message-ID: Date: Thu, 11 Jun 2026 07:00:20 +0930 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH btrfs v2] btrfs: reject free space cache with more entries than pages To: Xiang Mei , David Sterba , Chris Mason , linux-btrfs@vger.kernel.org Cc: Josef Bacik , Weiming Shi , linux-kernel@vger.kernel.org References: <20260610172926.844265-1-xmei5@asu.edu> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <20260610172926.844265-1-xmei5@asu.edu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/6/11 02:59, Xiang Mei 写道: > When loading a v1 free space cache, __load_free_space_cache() takes > num_entries and num_bitmaps straight from the on-disk > btrfs_free_space_header. That header is stored in the tree_root under a key > with type 0, which the tree-checker has no case for, so neither count is > validated before the load trusts it. > > The load loops num_entries times and maps the next page whenever the current > one runs out, going through io_ctl_check_crc() -> io_ctl_map_page(), which > does io_ctl->pages[io_ctl->index++]. But pages[] is allocated in > io_ctl_init() from the cache inode's i_size, not from num_entries: > > num_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); > io_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS); > > So if num_entries claims more records than the pages can hold, io_ctl->index > runs off the end of pages[]. The write side never hits this because > io_ctl_add_entry() and io_ctl_add_bitmap() both stop once > io_ctl->index >= io_ctl->num_pages; the read side just never had the same > check. > > To trigger it, take a clean cache (num_entries = here), set num_entries > in the header to 0x10000, and fix up the leaf checksum so it still passes > the tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and > pages[] is a 16-pointer (kmalloc-128) array. The load now tries to read > 65536 entries, io_ctl->index walks up to 16, and pages[16] is read past the > array: > > BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) > Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58 > io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) > __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820) > load_free_space_cache (fs/btrfs/free-space-cache.c:1017) > caching_thread (fs/btrfs/block-group.c:880) > btrfs_work_helper (fs/btrfs/async-thread.c:312) > process_one_work > worker_thread > kthread > ret_from_fork > > free-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc() > at line 565, which is why that is the frame KASAN names. The out-of-bounds > slot is then treated as a struct page and handed to crc32c(), so the bad > read turns into a GP fault. > > Add the missing check to io_ctl_check_crc(), which is where both the entry > loop and the bitmap loop end up. When num_entries is too large the load now > fails like any corrupt cache: __load_free_space_cache() drops it and rebuilds > the free space from the extent tree, so a valid cache is never rejected. > > Fixes: 5b0e95bf607d ("Btrfs: inline checksums into the disk free space cache") > Reported-by: Weiming Shi > Assisted-by: Claude:claude-opus-4-8 > Signed-off-by: Xiang Mei Reviewed-by: Qu Wenruo I'll add a Link: tag to the reproducer at merge time. But I still strongly prefer you guys to submit a bug report/reproducer before sending out a fix. > --- > v2: add more details in the commit message > > fs/btrfs/free-space-cache.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c > index ab22e4f9ffdd..bbc4db7fe74b 100644 > --- a/fs/btrfs/free-space-cache.c > +++ b/fs/btrfs/free-space-cache.c > @@ -555,6 +555,9 @@ static int io_ctl_check_crc(struct btrfs_io_ctl *io_ctl, int index) > u32 crc = ~(u32)0; > unsigned offset = 0; > > + if (index >= io_ctl->num_pages) > + return -EIO; > + > if (index == 0) > offset = sizeof(u32) * io_ctl->num_pages; >