The patch titled
security: prevent permission checking of file removal via sysfs_remove_group()
has been added to the -mm tree. Its filename is
security-prevent-permission-checking-of-file-removal-via-sysfs_remove_group.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: security: prevent permission checking of file removal via sysfs_remove_group()
From: James Morris <jmorris@xxxxxxxxx>
Prevent permission checking from being performed when the kernel wants to
unconditionally remove a sysfs group, by introducing an kernel-only variant
of lookup_one_len(), lookup_one_len_kern().
Additionally, as sysfs_remove_group() does not check the return value of
the lookup before using it, a BUG_ON has been added to pinpoint the cause
of any problems potentially caused by this (and as a form of annotation).
Signed-off-by: James Morris <jmorris@xxxxxxxxx>
Cc: Nagendra Singh Tomar <nagendra_tomar@xxxxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Cc: Tejun Heo <htejun@xxxxxxxxx>
Cc: Stephen Smalley <sds@xxxxxxxxxxxxx>
Cc: Eric Paris <eparis@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/namei.c | 72 ++++++++++++++++++++++++++++------------
fs/sysfs/group.c | 6 ++-
include/linux/namei.h | 1
3 files changed, 57 insertions(+), 22 deletions(-)
diff -puN fs/namei.c~security-prevent-permission-checking-of-file-removal-via-sysfs_remove_group fs/namei.c
--- a/fs/namei.c~security-prevent-permission-checking-of-file-removal-via-sysfs_remove_group
+++ a/fs/namei.c
@@ -1243,22 +1243,13 @@ int __user_path_lookup_open(const char _
return err;
}
-/*
- * Restricted form of lookup. Doesn't follow links, single-component only,
- * needs parent already locked. Doesn't follow mounts.
- * SMP-safe.
- */
-static struct dentry * __lookup_hash(struct qstr *name, struct dentry * base, struct nameidata *nd)
+static inline struct dentry *__lookup_hash_kern(struct qstr *name, struct dentry *base, struct nameidata *nd)
{
- struct dentry * dentry;
+ struct dentry *dentry;
struct inode *inode;
int err;
inode = base->d_inode;
- err = permission(inode, MAY_EXEC, nd);
- dentry = ERR_PTR(err);
- if (err)
- goto out;
/*
* See if the low-level filesystem might want
@@ -1287,35 +1278,76 @@ out:
return dentry;
}
+/*
+ * Restricted form of lookup. Doesn't follow links, single-component only,
+ * needs parent already locked. Doesn't follow mounts.
+ * SMP-safe.
+ */
+static inline struct dentry * __lookup_hash(struct qstr *name, struct dentry *base, struct nameidata *nd)
+{
+ struct dentry *dentry;
+ struct inode *inode;
+ int err;
+
+ inode = base->d_inode;
+
+ err = permission(inode, MAY_EXEC, nd);
+ dentry = ERR_PTR(err);
+ if (err)
+ goto out;
+
+ dentry = __lookup_hash_kern(name, base, nd);
+out:
+ return dentry;
+}
+
static struct dentry *lookup_hash(struct nameidata *nd)
{
return __lookup_hash(&nd->last, nd->dentry, nd);
}
/* SMP-safe */
-struct dentry * lookup_one_len(const char * name, struct dentry * base, int len)
+static inline int __lookup_one_len(const char *name, struct qstr *this, struct dentry *base, int len)
{
unsigned long hash;
- struct qstr this;
unsigned int c;
- this.name = name;
- this.len = len;
+ this->name = name;
+ this->len = len;
if (!len)
- goto access;
+ return -EACCES;
hash = init_name_hash();
while (len--) {
c = *(const unsigned char *)name++;
if (c == '/' || c == '\0')
- goto access;
+ return -EACCES;
hash = partial_name_hash(c, hash);
}
- this.hash = end_name_hash(hash);
+ this->hash = end_name_hash(hash);
+ return 0;
+}
+struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
+{
+ int err;
+ struct qstr this;
+
+ err = __lookup_one_len(name, &this, base, len);
+ if (err)
+ return ERR_PTR(err);
return __lookup_hash(&this, base, NULL);
-access:
- return ERR_PTR(-EACCES);
+}
+
+struct dentry *lookup_one_len_kern(const char *name, struct dentry *base, int len)
+{
+ int err;
+ struct qstr this;
+
+ err = __lookup_one_len(name, &this, base, len);
+ if (err)
+ return ERR_PTR(err);
+ return __lookup_hash_kern(&this, base, NULL);
}
/*
diff -puN fs/sysfs/group.c~security-prevent-permission-checking-of-file-removal-via-sysfs_remove_group fs/sysfs/group.c
--- a/fs/sysfs/group.c~security-prevent-permission-checking-of-file-removal-via-sysfs_remove_group
+++ a/fs/sysfs/group.c
@@ -70,9 +70,11 @@ void sysfs_remove_group(struct kobject *
{
struct dentry * dir;
- if (grp->name)
- dir = lookup_one_len(grp->name, kobj->dentry,
+ if (grp->name) {
+ dir = lookup_one_len_kern(grp->name, kobj->dentry,
strlen(grp->name));
+ BUG_ON(IS_ERR(dir));
+ }
else
dir = dget(kobj->dentry);
diff -puN include/linux/namei.h~security-prevent-permission-checking-of-file-removal-via-sysfs_remove_group include/linux/namei.h
--- a/include/linux/namei.h~security-prevent-permission-checking-of-file-removal-via-sysfs_remove_group
+++ a/include/linux/namei.h
@@ -82,6 +82,7 @@ extern struct file *nameidata_to_filp(st
extern void release_open_intent(struct nameidata *);
extern struct dentry * lookup_one_len(const char *, struct dentry *, int);
+extern struct dentry *lookup_one_len_kern(const char *, struct dentry *, int);
extern int follow_down(struct vfsmount **, struct dentry **);
extern int follow_up(struct vfsmount **, struct dentry **);
_
Patches currently in -mm which might be from jmorris@xxxxxxxxx are
return-eperm-not-echild-on-security_task_wait-failure.patch
security-prevent-permission-checking-of-file-removal-via-sysfs_remove_group.patch
git-net.patch
git-selinux.patch
implement-file-posix-capabilities.patch
file-capabilities-accomodate-future-64-bit-caps.patch
allow-access-to-proc-pid-fd-after-setuid.patch
tty-introduce-no_tty-and-use-it-in-selinux.patch
ignore-stolen-time-in-the-softlockup-watchdog.patch
remove-redundant-check-from-proc_setattr.patch
remove-redundant-check-from-proc_sys_setattr.patch
mprotect-patch-for-use-by-slim.patch
integrity-service-api-and-dummy-provider.patch
slim-main-patch.patch
slim-secfs-patch.patch
slim-make-and-config-stuff.patch
slim-debug-output.patch
slim-documentation.patch
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