From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) by lore.proxmox.com (Postfix) with ESMTPS id C23C01FF17C for ; Tue, 30 Dec 2025 13:41:25 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 97481B107; Tue, 30 Dec 2025 13:42:32 +0100 (CET) From: Robert Obkircher To: pbs-devel@lists.proxmox.com Date: Tue, 30 Dec 2025 13:39:49 +0100 Message-ID: <20251230124154.115442-3-r.obkircher@proxmox.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251230124154.115442-1-r.obkircher@proxmox.com> References: <20251230124154.115442-1-r.obkircher@proxmox.com> MIME-Version: 1.0 X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1767098522910 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.051 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: [pbs-devel] [PATCH v2 proxmox-backup 2/2] datastore: prevent potentially unaligned FixedIndexHeader reference X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Proxmox Backup Server development discussion Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: pbs-devel-bounces@lists.proxmox.com Sender: "pbs-devel" Continue to avoid the 4 KiB stack allocation in debug builds by adopting the approach used for the DynamicIndexHeader. This also avoid mutation through Vec::as_ptr, which is forbidden according to its documentation. Signed-off-by: Robert Obkircher --- pbs-datastore/src/fixed_index.rs | 35 ++++++++++++++++++++++++-------- 1 file changed, 27 insertions(+), 8 deletions(-) diff --git a/pbs-datastore/src/fixed_index.rs b/pbs-datastore/src/fixed_index.rs index 6c3be2d4..7241d77f 100644 --- a/pbs-datastore/src/fixed_index.rs +++ b/pbs-datastore/src/fixed_index.rs @@ -29,6 +29,31 @@ pub struct FixedIndexHeader { } proxmox_lang::static_assert_size!(FixedIndexHeader, 4096); +impl FixedIndexHeader { + /// Convenience method to allocate a zero-initialized header struct. + pub fn zeroed() -> Box { + let layout = std::alloc::Layout::new::(); + unsafe { + let ptr = std::alloc::alloc_zeroed(layout) as *mut Self; + if ptr.is_null() { + std::alloc::handle_alloc_error(layout); + } + Box::from_raw(ptr) + } + } + + pub fn as_bytes(&self) -> &[u8] { + unsafe { + // There can't be any uninitialized padding, because the fields + // take up all of the statically asserted total size. + std::slice::from_raw_parts( + self as *const Self as *const u8, + std::mem::size_of::(), + ) + } + } +} + // split image into fixed size chunks pub struct FixedIndexReader { @@ -237,7 +262,6 @@ impl Drop for FixedIndexWriter { } impl FixedIndexWriter { - #[allow(clippy::cast_ptr_alignment)] // Requires obtaining a shared chunk store lock beforehand pub fn create( store: Arc, @@ -267,18 +291,13 @@ impl FixedIndexWriter { let uuid = Uuid::generate(); - let buffer = vec![0u8; header_size]; - let header = unsafe { &mut *(buffer.as_ptr() as *mut FixedIndexHeader) }; - + let mut header = FixedIndexHeader::zeroed(); header.magic = file_formats::FIXED_SIZED_CHUNK_INDEX_1_0; header.ctime = i64::to_le(ctime); header.size = u64::to_le(size as u64); header.chunk_size = u64::to_le(chunk_size as u64); header.uuid = *uuid.as_bytes(); - - header.index_csum = [0u8; 32]; - - file.write_all(&buffer)?; + file.write_all(header.as_bytes())?; let index_length = size.div_ceil(chunk_size); let index_size = index_length * 32; -- 2.47.3 _______________________________________________ pbs-devel mailing list pbs-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel