From 96d6523adffbab64f099561a021892125e0c672c Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Thu, 8 Jul 2010 09:31:24 -0700 Subject: [PATCH] sysfs: Don't allow the creation of symlinks we can't remove Recently my tagged sysfs support revealed a flaw in the device core that a few rare drivers are running into such that we don't always put network devices in a class subdirectory named net/. Since we are not creating the class directory the network devices wind up in a non-tagged directory, but the symlinks to the network devices from /sys/class/net are in a tagged directory. All of which works until we go to remove or rename the symlink. When we remove or rename a symlink we look in the namespace of the target of the symlink. Since the target of the symlink is in a non-tagged sysfs directory we don't have a namespace to look in, and we fail to remove the symlink. Detect this problem up front and simply don't create symlinks we won't be able to remove later. This prevents symlink leakage and fails in a much clearer and more understandable way. Signed-off-by: Eric W. Biederman Cc: Andrew Morton Cc: Rafael J. Wysocki Cc: Maciej W. Rozycki Cc: Kay Sievers Cc: Johannes Berg Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/symlink.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c index f71246bebfe4..44bca5f49cd5 100644 --- a/fs/sysfs/symlink.c +++ b/fs/sysfs/symlink.c @@ -28,6 +28,7 @@ static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, struct sysfs_dirent *target_sd = NULL; struct sysfs_dirent *sd = NULL; struct sysfs_addrm_cxt acxt; + enum kobj_ns_type ns_type; int error; BUG_ON(!name); @@ -58,16 +59,28 @@ static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, if (!sd) goto out_put; - if (sysfs_ns_type(parent_sd)) + ns_type = sysfs_ns_type(parent_sd); + if (ns_type) sd->s_ns = target->ktype->namespace(target); sd->s_symlink.target_sd = target_sd; target_sd = NULL; /* reference is now owned by the symlink */ sysfs_addrm_start(&acxt, parent_sd); - if (warn) - error = sysfs_add_one(&acxt, sd); - else - error = __sysfs_add_one(&acxt, sd); + /* Symlinks must be between directories with the same ns_type */ + if (ns_type == sysfs_ns_type(sd->s_symlink.target_sd->s_parent)) { + if (warn) + error = sysfs_add_one(&acxt, sd); + else + error = __sysfs_add_one(&acxt, sd); + } else { + error = -EINVAL; + WARN(1, KERN_WARNING + "sysfs: symlink across ns_types %s/%s -> %s/%s\n", + parent_sd->s_name, + sd->s_name, + sd->s_symlink.target_sd->s_parent->s_name, + sd->s_symlink.target_sd->s_name); + } sysfs_addrm_finish(&acxt); if (error) -- 2.20.1