The patch titled
sysfs group: bypass permission checks
has been removed from the -mm tree. Its filename was
sysfs-group-removal-avoid-bypass-permission-checks.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
Subject: sysfs group: bypass permission checks
From: James Morris <jmorris@xxxxxxxxx>
Prevent permission checking from being peformed 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: Tejun Heo <htejun@xxxxxxxxx>
Cc: Stephen Smalley <sds@xxxxxxxxxxxxx>
Cc: Eric Paris <eparis@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/namei.c | 30 ++++++++++++++++++++++--------
fs/sysfs/group.c | 6 ++++--
include/linux/namei.h | 3 ++-
3 files changed, 28 insertions(+), 11 deletions(-)
diff -puN fs/namei.c~sysfs-group-removal-avoid-bypass-permission-checks fs/namei.c
--- a/fs/namei.c~sysfs-group-removal-avoid-bypass-permission-checks
+++ a/fs/namei.c
@@ -1248,17 +1248,20 @@ int __user_path_lookup_open(const char _
* 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 struct dentry * __lookup_hash(struct qstr *name, struct dentry * base, struct nameidata *nd, int kern)
{
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;
+
+ if (likely(!kern)) {
+ err = permission(inode, MAY_EXEC, nd);
+ dentry = ERR_PTR(err);
+ if (err)
+ goto out;
+ }
/*
* See if the low-level filesystem might want
@@ -1289,11 +1292,11 @@ out:
static struct dentry *lookup_hash(struct nameidata *nd)
{
- return __lookup_hash(&nd->last, nd->dentry, nd);
+ return __lookup_hash(&nd->last, nd->dentry, nd, 0);
}
/* SMP-safe */
-struct dentry * lookup_one_len(const char * name, struct dentry * base, int len)
+static inline struct dentry * __lookup_one_len(const char * name, struct dentry * base, int len, int kern)
{
unsigned long hash;
struct qstr this;
@@ -1313,11 +1316,22 @@ struct dentry * lookup_one_len(const cha
}
this.hash = end_name_hash(hash);
- return __lookup_hash(&this, base, NULL);
+ return __lookup_hash(&this, base, NULL, kern);
access:
return ERR_PTR(-EACCES);
}
+struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
+{
+ return __lookup_one_len(name, base, len, 0);
+}
+
+struct dentry *lookup_one_len_kern(const char *name, struct dentry *base,
+ int len)
+{
+ return __lookup_one_len(name, base, len, 1);
+}
+
/*
* namei()
*
diff -puN fs/sysfs/group.c~sysfs-group-removal-avoid-bypass-permission-checks fs/sysfs/group.c
--- a/fs/sysfs/group.c~sysfs-group-removal-avoid-bypass-permission-checks
+++ 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~sysfs-group-removal-avoid-bypass-permission-checks include/linux/namei.h
--- a/include/linux/namei.h~sysfs-group-removal-avoid-bypass-permission-checks
+++ a/include/linux/namei.h
@@ -81,7 +81,8 @@ extern struct file *lookup_instantiate_f
extern struct file *nameidata_to_filp(struct nameidata *nd, int flags);
extern void release_open_intent(struct nameidata *);
-extern struct dentry * lookup_one_len(const char *, struct dentry *, int);
+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
sysfs-group-removal-avoid-bypass-permission-checks.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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