From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [IPv6:2a01:7e0:0:424::9]) by lore.proxmox.com (Postfix) with ESMTPS id EC9041FF165 for ; Thu, 6 Nov 2025 13:55:02 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id C255C15E96; Thu, 6 Nov 2025 13:55:43 +0100 (CET) From: Christian Ebner To: pbs-devel@lists.proxmox.com Date: Thu, 6 Nov 2025 13:54:58 +0100 Message-ID: <20251106125458.479328-1-c.ebner@proxmox.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1762433692455 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.047 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 proxmox-backup] chunk store: fix race window between chunk stat and gc cleanup 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" Sweeping of unused chunks during garbage collection checks their atime to distinguish between chunks being in-use and chunks no longer being used. While garbage collection does lock the chunk store by guarding its mutex before reading file stats and deleting unused chunks, the conditional touch did not do this before updating the chunks atime (thereby also checking the presence). Therefore there is a race window between the chunks metadata being read and the chunk being removed, but the chunk being touched in-between. The race is however rare, as for this to happen the chunk must be older than the cutoff time and not be referenced by any index file, otherwise the atime would be updated during phase 1 already. Fix by guarding the chunk store mutex before touching a chunk. Signed-off-by: Christian Ebner --- pbs-datastore/src/chunk_store.rs | 1 + 1 file changed, 1 insertion(+) diff --git a/pbs-datastore/src/chunk_store.rs b/pbs-datastore/src/chunk_store.rs index ba7618e40..d21db4a71 100644 --- a/pbs-datastore/src/chunk_store.rs +++ b/pbs-datastore/src/chunk_store.rs @@ -217,6 +217,7 @@ impl ChunkStore { assert!(self.locker.is_some()); let (chunk_path, _digest_str) = self.chunk_path(digest); + let _lock = self.mutex.lock(); self.cond_touch_path(&chunk_path, assert_exists) } -- 2.47.3 _______________________________________________ pbs-devel mailing list pbs-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel