sysfs: Complain bitterly about attempts to remove files from nonexistent directories.

commit ce597919361dcec97341151690e780eade2a9cf4 upstream.

Recently an OOPS was observed from the usb serial io_ti driver when it tried to remove
sysfs directories.  Upon investigation it turns out this driver was always buggy
and that a recent sysfs change had stopped guarding itself against removing attributes
from sysfs directories that had already been removed. :(

Historically we have been silent about attempting to files from nonexistent sysfs
directories and have politely returned error codes.  That has resulted in people writing
broken code that ignores the error codes.

Issue a kernel WARNING and a stack backtrace to make it clear in no uncertain
terms that abusing sysfs is not ok, and the callers need to fix their code.

This change transforms the io_ti OOPS into a more comprehensible error message
and stack backtrace.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Reported-by: Wolfgang Frisch <wfpub@roembden.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index d4e6080b4b2053fae16fd451d01b6b20f813906f..779789af6e9009055b6bfc7bd45c804b5ec12155 100644 (file)
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -493,6 +493,12 @@ int sysfs_attr_ns(struct kobject *kobj, const struct attribute *attr,
        const void *ns = NULL;
        int err;
 
+       if (!dir_sd) {
+               WARN(1, KERN_ERR "sysfs: kobject %s without dirent\n",
+                       kobject_name(kobj));
+               return -ENOENT;
+       }
+
        err = 0;
        if (!sysfs_ns_type(dir_sd))
                goto out;

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index c81b22f3ace162629e790ee4e06941861b97e576..deb804bec9df699c1f30faf4d6d645f51dee7878 100644 (file)
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -318,8 +318,11 @@ int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const void *ns, const cha
        struct sysfs_addrm_cxt acxt;
        struct sysfs_dirent *sd;
 
-       if (!dir_sd)
+       if (!dir_sd) {
+               WARN(1, KERN_WARNING "sysfs: can not remove '%s', no directory\n",
+                       name);
                return -ENOENT;
+       }
 
        sysfs_addrm_start(&acxt, dir_sd);