linux-kernel - [PATCH v4 2/2] loop: use vfs_getattr

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20250814191004.60340-2-rajeevm@hpe.com>
Date: Thu, 14 Aug 2025 19:10:04 +0000
From: Rajeev Mishra <rajeevm@....com>
To: axboe@...nel.dk, yukuai1@...weicloud.com
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rajeev Mishra <rajeevm@....com>
Subject: [PATCH v4 2/2] loop: use vfs_getattr_nosec for accurate file size

- Use vfs_getattr_nosec() instead of i_size_read() in lo_calculate_size.
- Improves accuracy for network/distributed filesystems.

Signed-off-by: Rajeev Mishra <rajeevm@....com>
---
 drivers/block/loop.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 0e1b9eb9db10..57263c273f0f 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -139,9 +139,20 @@ static int part_shift;
 
 static loff_t lo_calculate_size(struct loop_device *lo, struct file *file)
 {
+	struct kstat stat;
 	loff_t loopsize;
-	/* Compute loopsize in bytes */
-	loopsize = i_size_read(file->f_mapping->host);
+	int ret;
+
+	/*
+	 * Get the accurate file size. This provides better results than
+	 * cached inode data, particularly for network filesystems where
+	 * metadata may be stale.
+	 */
+	ret = vfs_getattr_nosec(&file->f_path, &stat, STATX_SIZE, 0);
+	if (ret)
+		return 0;
+
+	loopsize = stat.size;
 	if (lo->lo_offset > 0)
 		loopsize -= lo->lo_offset;
 	/* offset is beyond i_size, weird but possible */
-- 
2.43.7