From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 19E553FADF1; Thu, 30 Jul 2026 14:57:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785423428; cv=none; b=sEkO4AAN0LPF2MWPZg9KYomQ1kbOosuRwnlQSllkCJso5ikueykcW9YOmWVP14c3v2TlwPfTxsYI58rA7o2GhFmsY2iO2BhE41Jp24zAR71pmviKSv94yQQCwtAySXcwX5kbT2fBTgSvnNDn5X+p6fAHKZ4E9OWXt1TLy03WX0Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785423428; c=relaxed/simple; bh=9sqU/nVkfw/ozVJbQR1/un7Bqo/XzvlI34tTTVV2MW0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FvbCRX19HZ+2X4ADBtos+87m2X3e9S0eoo1xXplcuB9XkCL8ABYkC4H1A2ZKeKfE4Yokq9TxCQV3FvPpYY2JiYeS/ncYLSEEB9RY4wP9R2U+zj4UBdOpgULzG8xgd0AYw61u6xm3zpqV1D8nOlbGL5iNIpsh4snOD/YrNN2fpwc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=g8fVnjHm; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="g8fVnjHm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74B4A1F000E9; Thu, 30 Jul 2026 14:57:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785423427; bh=70OUXJg7a9qsO9QUyXPllM4qwCD8tATCYevLneTFzg8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=g8fVnjHmBLUc8umvILAzKq0Kj3Fv/5AZ58YqjqAJLLx2qNRwaR6sZuQ078Dc6p96R 3F5wHnxFrCkconkYXReb/cESz+eTI8uX1qp/XofePwhUipxJEyvZFWQuiAbrIDtE7K Q2ILI9jsJBN+CFbc3K8FrQjVRCNCb1fElKy4Zo0I= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Weiming Shi , Qu Wenruo , Xiang Mei , David Sterba , Sasha Levin Subject: [PATCH 6.18 041/675] btrfs: reject free space cache with more entries than pages Date: Thu, 30 Jul 2026 16:06:11 +0200 Message-ID: <20260730141445.992791031@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141445.110192266@linuxfoundation.org> References: <20260730141445.110192266@linuxfoundation.org> User-Agent: quilt/0.69 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xiang Mei [ Upstream commit a2d8d5647ed854e38f941741aea45b9eb15a6350 ] 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. Reported-by: Weiming Shi Fixes: 5b0e95bf607d ("Btrfs: inline checksums into the disk free space cache") Link: https://lore.kernel.org/linux-btrfs/CAPpSM+RMPByMCKXvM5QFKToxsyNccfuFLWMdD0mfd0wh2Ja62w@mail.gmail.com/ Assisted-by: Claude:claude-opus-4-8 Reviewed-by: Qu Wenruo Signed-off-by: Xiang Mei Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- 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 ab873bd6719209..9828da12765f5c 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -554,6 +554,9 @@ 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; -- 2.53.0