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bh=5ZUCy55q9KblG6Yxl4AgPFOIbNt0FWb6Pj37J+0otzM=; b=DIeGCUAqFRTpPyBbO+R87SECdQgCVQsyPwGUVf8BIj8fzQGAjvj1nM2s37yz0kyR6Sophj V7+c6BIH4XU/vKfDmgKjjEnCxMwSpUNvoKDKmLDNAsFrgMR6zFwZ0a9ATgCNAJVMgCyJFF hqNAfKlgTzddkuBvUpmNXNZO0XYBw6lmuiJKBC/1oEYD82xki2X9P3VsvtRGLfbRAA5LbF C1VxZkNKiXRd78Vy4+KXmSZ6z2xJuJcdJTsnEVljyl0Gp88dc8Zi/kgk8KloPhhybdcbeP 2zVzlHoUUAyUyFzo3vBmUTvKAScvQphegxGtiA5NmCT8VnCDinkw2Fnd+07e+w== Message-ID: Date: Fri, 28 Feb 2025 15:43:32 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: [PATCH 1/2] configfs: Add mechanism to prevent symlink deletion To: =?UTF-8?B?Sm9zw6kgRXhww7NzaXRv?= Cc: hamohammed.sa@gmail.com, simona@ffwll.ch, melissa.srw@gmail.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20250225175936.7223-1-jose.exposito89@gmail.com> <20250225175936.7223-4-jose.exposito89@gmail.com> Content-Language: en-US From: Louis Chauvet Autocrypt: addr=louis.chauvet@bootlin.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgdeltdeiiecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfitefpfffkpdcuggftfghnshhusghstghrihgsvgenuceurghilhhouhhtmecufedtudenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepkfffgggfuffvvehfhfgjtgfgsehtjeertddtvdejnecuhfhrohhmpefnohhuihhsucevhhgruhhvvghtuceolhhouhhishdrtghhrghuvhgvthessghoohhtlhhinhdrtghomheqnecuggftrfgrthhtvghrnhepgfffveeuudeuhfekteeuhefhhedtleejgeehheduheeigfejteetueeifeehveevnecukfhppeeltddrkeelrdduieefrdduvdejnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepledtrdekledrudeifedruddvjedphhgvlhhopegludelvddrudeikedrtddrvddtngdpmhgrihhlfhhrohhmpehlohhuihhsrdgthhgruhhvvghtsegsohhothhlihhnrdgtohhmpdhnsggprhgtphhtthhopedutddprhgtphhtthhopehjohhsvgdrvgigphhoshhithhokeelsehgmhgrihhlrdgtohhmpdhrtghpthhtohephhgrmhhohhgrmhhmvggurdhsrgesghhmrghilhdrtghomhdprhgtphhtthhopehsihhmohhnrgesfhhffihllhdrtghhpdhrtghpthhtohepmhgvlhhishhsrgdrshhrfiesghhmrghilhdrtghomhdprhgtphhtthhopehmrggrrhhtvghnrdhlrghnkhhhohhrshhtsehlihhnu higrdhinhhtvghlrdgtohhmpdhrtghpthhtohepmhhrihhprghrugeskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepthiiihhmmhgvrhhmrghnnhesshhushgvrdguvgdprhgtphhtthhopegrihhrlhhivggusehgmhgrihhlrdgtohhm X-GND-Sasl: louis.chauvet@bootlin.com Introduce a new mechanism in configfs to prevent the deletion of certain symlink. This is particularly useful in scenarios where userspace should not be allowed to modify the configfs structure under some conditions, such as in VKMS. Signed-off-by: Louis Chauvet --- drivers/gpu/drm/vkms/vkms_configfs.c | 20 ++++++++++++++++++++ fs/configfs/symlink.c | 12 +++++++++--- include/linux/configfs.h | 1 + 3 files changed, 30 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c index f0813536be12..8a7d954399e9 100644 --- a/drivers/gpu/drm/vkms/vkms_configfs.c +++ b/drivers/gpu/drm/vkms/vkms_configfs.c @@ -295,8 +295,28 @@ static void plane_possible_crtcs_drop_link(struct config_item *src, mutex_unlock(&plane->dev->lock); } +static int plane_possible_crtcs_allow_drop_link(struct config_item *src, + struct config_item *target) +{ + struct vkms_configfs_plane *plane; + struct vkms_configfs_crtc *crtc; + bool enabled; + + plane = plane_possible_crtcs_item_to_vkms_configfs_plane(src); + crtc = crtc_item_to_vkms_configfs_crtc(target); + + mutex_lock(&plane->dev->lock); + enabled = plane->dev->enabled; + mutex_unlock(&plane->dev->lock); + + if (enabled) + return -EBUSY; + return 0; +} + static struct configfs_item_operations plane_possible_crtcs_item_operations = { .allow_link = plane_possible_crtcs_allow_link, + .allow_drop_link = plane_possible_crtcs_allow_drop_link, .drop_link = plane_possible_crtcs_drop_link, }; diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c index 69133ec1fac2..925e2e15eb9b 100644 --- a/fs/configfs/symlink.c +++ b/fs/configfs/symlink.c @@ -233,6 +233,13 @@ int configfs_unlink(struct inode *dir, struct dentry *dentry) parent_item = configfs_get_config_item(dentry->d_parent); type = parent_item->ci_type; + if (type && type->ct_item_ops && + type->ct_item_ops->allow_drop_link) { + ret = type->ct_item_ops->allow_drop_link(parent_item, target_sd->s_element); + if (ret) + goto out_put; + } + spin_lock(&configfs_dirent_lock); list_del_init(&sd->s_sibling); spin_unlock(&configfs_dirent_lock); @@ -255,10 +262,9 @@ int configfs_unlink(struct inode *dir, struct dentry *dentry) spin_unlock(&configfs_dirent_lock); configfs_put(target_sd); - config_item_put(parent_item); - ret = 0; - +out_put: + config_item_put(parent_item); out: return ret; } diff --git a/include/linux/configfs.h b/include/linux/configfs.h index c771e9d0d0b9..7fc52a78d6cd 100644 --- a/include/linux/configfs.h +++ b/include/linux/configfs.h @@ -208,6 +208,7 @@ static struct configfs_bin_attribute _pfx##attr_##_name = { \ struct configfs_item_operations { void (*release)(struct config_item *); int (*allow_link)(struct config_item *src, struct config_item *target); + int (*allow_drop_link)(struct config_item *src, struct config_item *target); void (*drop_link)(struct config_item *src, struct config_item *target); }; -- 2.48.1