linux-kernel - [PATCH v2 0/2] vfs: output mount_too

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Message-Id: <20250806-errorfc-mount-too-revealing-v2-0-534b9b4d45bb@cyphar.com>
Date: Wed, 06 Aug 2025 16:07:04 +1000
From: Aleksa Sarai <cyphar@...har.com>
To: Alexander Viro <viro@...iv.linux.org.uk>, 
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>
Cc: David Howells <dhowells@...hat.com>, linux-api@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
 Aleksa Sarai <cyphar@...har.com>
Subject: [PATCH v2 0/2] vfs: output mount_too_revealing() errors to
 fscontext

It makes little sense for fsmount() to output the warning message when
mount_too_revealing() is violated to kmsg. Instead, the warning should
be output (with a "VFS" prefix) to the fscontext log. In addition,
include the same log message for mount_too_revealing() when doing a
regular mount for consistency.

With the newest fsopen()-based mount(8) from util-linux, the error
messages now look like

  # mount -t proc proc /tmp
  mount: /tmp: fsmount() failed: VFS: Mount too revealing.
	 dmesg(1) may have more information after failed mount system call.

which could finally result in mount_too_revealing() errors being easier
for users to detect and understand.

Signed-off-by: Aleksa Sarai <cyphar@...har.com>
---
Changes in v2:
- Log before setting retval. [Al Viro]
- v1: <https://lore.kernel.org/r/20250806-errorfc-mount-too-revealing-v1-0-536540f51560@cyphar.com>

---
Aleksa Sarai (2):
      fscontext: add custom-prefix log helpers
      vfs: output mount_too_revealing() errors to fscontext

 fs/namespace.c             |  6 ++++--
 include/linux/fs_context.h | 18 ++++++++++++++----
 2 files changed, 18 insertions(+), 6 deletions(-)
---
base-commit: 66639db858112bf6b0f76677f7517643d586e575
change-id: 20250805-errorfc-mount-too-revealing-5d9f670ba770

Best regards,
-- 
Aleksa Sarai <cyphar@...har.com>