From 5d9808679bd221ee67dc0c8feb81793873127e84 Mon Sep 17 00:00:00 2001
From: Cristian Scheid <cristianscheid@gmail.com>
Date: Fri, 23 Oct 2026 10:30:42 -0300
Subject: [PATCH] fix(files): skip quota check when opening files for reading

Signed-off-by: Cristian Scheid <cristianscheid@gmail.com>
---
 lib/private/Files/Storage/Wrapper/Quota.php   |  8 ++++++--
 tests/lib/Files/Storage/Wrapper/QuotaTest.php | 17 +++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/lib/private/Files/Storage/Wrapper/Quota.php b/lib/private/Files/Storage/Wrapper/Quota.php
index 35a265f8c8e72..c9e59a754a5dc 100644
--- a/lib/private/Files/Storage/Wrapper/Quota.php
+++ b/lib/private/Files/Storage/Wrapper/Quota.php
@@ -116,7 +116,9 @@ public function copy(string $source, string $target): bool {
 	}
 
 	public function fopen(string $path, string $mode) {
-		if (!$this->hasQuota()) {
+		// reading doesn't consume quota, so it should not be restricted by it
+		$isReadMode = $mode === 'r' || $mode === 'rb';
+		if ($isReadMode || !$this->hasQuota()) {
 			return $this->storage->fopen($path, $mode);
 		}
 		$source = $this->storage->fopen($path, $mode);
@@ -124,7 +126,9 @@ public function fopen(string $path, string $mode) {
 		// don't apply quota for part files
 		if (!$this->isPartFile($path)) {
 			$free = $this->free_space($path);
-			if ($source && (is_int($free) || is_float($free)) && $free >= 0 && $mode !== 'r' && $mode !== 'rb') {
+			// writing past the remaining free space fails. Negative values mean the free
+			// space is unknown or unlimited (FileInfo::SPACE_*), so no limit is applied
+			if ($source && (is_int($free) || is_float($free)) && $free >= 0) {
 				// only apply quota for files, not metadata, trash or others
 				if ($this->shouldApplyQuota($path)) {
 					return \OC\Files\Stream\Quota::wrap($source, $free);
diff --git a/tests/lib/Files/Storage/Wrapper/QuotaTest.php b/tests/lib/Files/Storage/Wrapper/QuotaTest.php
index 3d313666a93b0..ccc03affb776a 100644
--- a/tests/lib/Files/Storage/Wrapper/QuotaTest.php
+++ b/tests/lib/Files/Storage/Wrapper/QuotaTest.php
@@ -166,6 +166,23 @@ public function testReturnRegularStreamOnRead(): void {
 		fclose($stream);
 	}
 
+	public function testFopenReadWhenQuotaExceeded(): void {
+		$instance = $this->getLimitedStorage(3);
+
+		// write foobar (6 bytes) past the quota wrapper and scan it,
+		// so the cached usage exceeds the 3 bytes quota
+		$instance->getWrapperStorage()->file_put_contents('files/foo', 'foobar');
+		$instance->getWrapperStorage()->getScanner()->scan('');
+		$this->assertEquals(0, $instance->free_space('files'));
+
+		foreach (['r', 'rb'] as $mode) {
+			$stream = $instance->fopen('files/foo', $mode);
+			$this->assertIsResource($stream);
+			$this->assertEquals('foobar', stream_get_contents($stream));
+			fclose($stream);
+		}
+	}
+
 	public function testReturnRegularStreamWhenOutsideFiles(): void {
 		$instance = $this->getLimitedStorage(9);
 		$instance->mkdir('files_other');