From: Jason Gunthorpe <jgg@nvidia.com>
To: Tzung-Bi Shih <tzungbi@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Benson Leung <bleung@chromium.org>,
linux-kernel@vger.kernel.org, chrome-platform@lists.linux.dev,
"Rafael J. Wysocki" <rafael@kernel.org>,
Danilo Krummrich <dakr@kernel.org>,
Jonathan Corbet <corbet@lwn.net>, Shuah Khan <shuah@kernel.org>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Wolfram Sang <wsa+renesas@sang-engineering.com>,
Johan Hovold <johan@kernel.org>,
"Paul E . McKenney" <paulmck@kernel.org>,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH 3/8] char: misc: Introduce misc_sync_register()
Date: Tue, 28 Apr 2026 13:09:56 -0300 [thread overview]
Message-ID: <20260428160956.GC718365@nvidia.com> (raw)
In-Reply-To: <20260427134659.95181-4-tzungbi@kernel.org>
On Mon, Apr 27, 2026 at 09:46:54PM +0800, Tzung-Bi Shih wrote:
> Introduce misc_sync_register() to support synchronous file operations
> for misc devices. This aims to prevent Use-After-Free errors when a
> device is deregistered while file operations are still in progress or
> files are open.
>
> It creates a synchronization context that wraps supported file
> operations and ensures the device is still registered before invoking
> the file operations.
>
> The minor number is deferred from being freed immediately on
> deregistration and is used as a primary key to search for the
> synchronization context in `misc_sync_ctx_list` after the device is
> unregistered.
>
> Performance impact:
> - All file operations are serialized by a global lock.
> - All file operations perform a linear search to find the corresponding
> miscdevice.
This doesn't seem like a serious proposal, this is too much
performance cost.
Jason
next prev parent reply other threads:[~2026-04-28 16:10 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-27 13:46 [PATCH 0/8] char: misc: Introduce misc_sync to fix UAF Tzung-Bi Shih
2026-04-27 13:46 ` [PATCH 1/8] char: misc: Simplify locking with guard() Tzung-Bi Shih
2026-04-27 13:46 ` [PATCH 2/8] char: misc: Introduce misc_find() helper Tzung-Bi Shih
2026-04-27 13:46 ` [PATCH 3/8] char: misc: Introduce misc_sync_register() Tzung-Bi Shih
2026-04-28 16:09 ` Jason Gunthorpe [this message]
2026-05-08 9:38 ` Tzung-Bi Shih
2026-05-08 11:54 ` Jason Gunthorpe
2026-05-09 9:40 ` Tzung-Bi Shih
2026-05-09 16:32 ` Jason Gunthorpe
2026-04-27 13:46 ` [PATCH 4/8] char: misc: Use SRCU to protect list traversal Tzung-Bi Shih
2026-04-27 13:46 ` [PATCH 5/8] platform/chrome: cros_ec_chardev: Introduce chardev_data Tzung-Bi Shih
2026-04-27 13:46 ` [PATCH 6/8] platform/chrome: cros_ec_chardev: Move data to chardev_pdata Tzung-Bi Shih
2026-04-27 13:46 ` [PATCH 7/8] platform/chrome: cros_ec_chardev: Add event relayer Tzung-Bi Shih
2026-04-27 13:46 ` [PATCH 8/8] platform/chrome: cros_ec_chardev: Use misc_sync_register() Tzung-Bi Shih
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