linux-kernel - [PATCH] fs: drop assert in file_seek_cur_needs_f

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Message-ID: <20250612094101.6003-1-luis@igalia.com>
Date: Thu, 12 Jun 2025 10:41:01 +0100
From: Luis Henriques <luis@...lia.com>
To: Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	kernel-dev@...lia.com,
	Luis Henriques <luis@...lia.com>
Subject: [PATCH] fs: drop assert in file_seek_cur_needs_f_lock

The assert in function file_seek_cur_needs_f_lock() can be triggered very
easily because, as Jan Kara suggested, the file reference may get
incremented after checking it with fdget_pos().

Fixes: da06e3c51794 ("fs: don't needlessly acquire f_lock")
Signed-off-by: Luis Henriques <luis@...lia.com>
---
Hi Christian,

It wasn't clear whether you'd be queueing this fix yourself.  Since I don't
see it on vfs.git, I decided to explicitly send the patch so that it doesn't
slip through the cracks.

Cheers,
-- 
Luis

 fs/file.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index 3a3146664cf3..075f07bdc977 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -1198,8 +1198,6 @@ bool file_seek_cur_needs_f_lock(struct file *file)
 	if (!(file->f_mode & FMODE_ATOMIC_POS) && !file->f_op->iterate_shared)
 		return false;
 
-	VFS_WARN_ON_ONCE((file_count(file) > 1) &&
-			 !mutex_is_locked(&file->f_pos_lock));
 	return true;
 }