[PATCH 1/1] file capabilities: clear fcaps on inode change (v4)

From: Serge E . Hallyn
Date: Tue Aug 07 2007 - 21:41:35 EST

Next message: Henrique de Moraes Holschuh: "Re: Disk spin down issue on shut down/suspend to disk"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

When a file with posix capabilities is overwritten, the
file capabilities, like a setuid bit, should be removed.

This patch introduces security_inode_killpriv(). This is
currently only defined for capability, and is called when
an inode is changed to inform the security module that
it may want to clear out any privilege attached to that inode.
The capability module checks whether any file capabilities
are defined for the inode, and, if so, clears them.

Changelog:
* Split security_inode_killpriv() into two hooks so as
to avoid grabbing inode->i_mutex needlessly in
generic_file_splice_write().
* Removed needlock argument to killpriv, require
inode->i_mutex to be held when security_inode_killpriv()
is called.
* Defined security_inode_killpriv to call killpriv() in
secondary_ops.

Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>
---
fs/attr.c | 9 +++++++++
fs/nfsd/vfs.c | 4 ++--
fs/open.c | 3 ++-
fs/splice.c | 13 +++++++++----
include/linux/fs.h | 1 +
include/linux/security.h | 28 ++++++++++++++++++++++++++++
mm/filemap.c | 14 ++++++++++----
security/capability.c | 2 ++
security/commoncap.c | 35 +++++++++++++++++++++++++++++++++++
security/dummy.c | 12 ++++++++++++
security/security.c | 10 ++++++++++
security/selinux/hooks.c | 12 ++++++++++++
12 files changed, 132 insertions(+), 11 deletions(-)

diff --git a/fs/attr.c b/fs/attr.c
index f8dfc22..ae58bd3 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -116,6 +116,15 @@ int notify_change(struct dentry * dentry, struct iattr * attr)
attr->ia_atime = now;
if (!(ia_valid & ATTR_MTIME_SET))
attr->ia_mtime = now;
+ if (ia_valid & ATTR_KILL_PRIV) {
+ attr->ia_valid &= ~ATTR_KILL_PRIV;
+ ia_valid &= ~ATTR_KILL_PRIV;
+ error = security_inode_need_killpriv(dentry);
+ if (error > 0)
+ error = security_inode_killpriv(dentry);
+ if (error)
+ return error;
+ }
if (ia_valid & ATTR_KILL_SUID) {
attr->ia_valid &= ~ATTR_KILL_SUID;
if (mode & S_ISUID) {
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ee96a89..33d1476 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -364,7 +364,7 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,

/* Revoke setuid/setgid bit on chown/chgrp */
if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid)
- iap->ia_valid |= ATTR_KILL_SUID;
+ iap->ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV;
if ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)
iap->ia_valid |= ATTR_KILL_SGID;

@@ -921,7 +921,7 @@ out:
static void kill_suid(struct dentry *dentry)
{
struct iattr ia;
- ia.ia_valid = ATTR_KILL_SUID | ATTR_KILL_SGID;
+ ia.ia_valid = ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;

mutex_lock(&dentry->d_inode->i_mutex);
notify_change(dentry, &ia);
diff --git a/fs/open.c b/fs/open.c
index 0e2e7b1..23f334d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -658,7 +658,8 @@ static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
newattrs.ia_gid = group;
}
if (!S_ISDIR(inode->i_mode))
- newattrs.ia_valid |= ATTR_KILL_SUID|ATTR_KILL_SGID;
+ newattrs.ia_valid |=
+ ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
mutex_lock(&inode->i_mutex);
error = notify_change(dentry, &newattrs);
mutex_unlock(&inode->i_mutex);
diff --git a/fs/splice.c b/fs/splice.c
index e36c003..ef95b48 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -824,13 +824,18 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
{
struct address_space *mapping = out->f_mapping;
struct inode *inode = mapping->host;
+ int killsuid, killpriv;
ssize_t ret;
- int err;
+ int err = 0;

- err = should_remove_suid(out->f_path.dentry);
- if (unlikely(err)) {
+ killpriv = security_inode_need_killpriv(out->f_path.dentry);
+ killsuid = should_remove_suid(out->f_path.dentry);
+ if (unlikely(killsuid || killpriv)) {
mutex_lock(&inode->i_mutex);
- err = __remove_suid(out->f_path.dentry, err);
+ if (killpriv)
+ err = security_inode_killpriv(out->f_path.dentry);
+ if (!err && killsuid)
+ err = __remove_suid(out->f_path.dentry, killsuid);
mutex_unlock(&inode->i_mutex);
if (err)
return err;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3d99c04..609c40a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -335,6 +335,7 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
#define ATTR_KILL_SUID 2048
#define ATTR_KILL_SGID 4096
#define ATTR_FILE 8192
+#define ATTR_KILL_PRIV 16384

/*
* This is the Inode Attributes structure, used for notify_change(). It
diff --git a/include/linux/security.h b/include/linux/security.h
index 0a28da7..e38230f 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -51,6 +51,8 @@ extern void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe);
extern int cap_bprm_secureexec(struct linux_binprm *bprm);
extern int cap_inode_setxattr(struct dentry *dentry, char *name, void *value, size_t size, int flags);
extern int cap_inode_removexattr(struct dentry *dentry, char *name);
+extern int cap_inode_need_killpriv(struct dentry *dentry);
+extern int cap_inode_killpriv(struct dentry *dentry);
extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
extern void cap_task_reparent_to_init (struct task_struct *p);
extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int sig, u32 secid);
@@ -417,6 +419,18 @@ struct request_sock;
* is specified by @buffer_size. @buffer may be NULL to request
* the size of the buffer required.
* Returns number of bytes used/required on success.
+ * @inode_need_killpriv:
+ * Called when an inode has been changed.
+ * @dentry is the dentry being changed.
+ * Return <0 on error to abort the inode change operation.
+ * Return 0 if inode_killpriv does not need to be called.
+ * Return >0 if inode_killpriv does need to be called.
+ * @inode_killpriv:
+ * The setuid bit is being removed. Remove similar security labels.
+ * Called with the dentry->d_inode->i_mutex held.
+ * @dentry is the dentry being changed.
+ * Return 0 on success. If error is returned, then the operation
+ * causing setuid bit removal is failed.
*
* Security hooks for file operations
*
@@ -1235,6 +1249,8 @@ struct security_operations {
int (*inode_getxattr) (struct dentry *dentry, char *name);
int (*inode_listxattr) (struct dentry *dentry);
int (*inode_removexattr) (struct dentry *dentry, char *name);
+ int (*inode_need_killpriv) (struct dentry *dentry);
+ int (*inode_killpriv) (struct dentry *dentry);
const char *(*inode_xattr_getsuffix) (void);
int (*inode_getsecurity)(const struct inode *inode, const char *name, void *buffer, size_t size, int err);
int (*inode_setsecurity)(struct inode *inode, const char *name, const void *value, size_t size, int flags);
@@ -1490,6 +1506,8 @@ void security_inode_post_setxattr(struct dentry *dentry, char *name,
int security_inode_getxattr(struct dentry *dentry, char *name);
int security_inode_listxattr(struct dentry *dentry);
int security_inode_removexattr(struct dentry *dentry, char *name);
+int security_inode_need_killpriv(struct dentry *dentry);
+int security_inode_killpriv(struct dentry *dentry);
const char *security_inode_xattr_getsuffix(void);
int security_inode_getsecurity(const struct inode *inode, const char *name, void *buffer, size_t size, int err);
int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags);
@@ -1879,6 +1897,16 @@ static inline int security_inode_removexattr (struct dentry *dentry, char *name)
return cap_inode_removexattr(dentry, name);
}

+static inline int security_inode_need_killpriv(struct dentry *dentry)
+{
+ return cap_inode_need_killpriv(dentry);
+}
+
+static inline int security_inode_killpriv(struct dentry *dentry)
+{
+ return cap_inode_killpriv(dentry);
+}
+
static inline const char *security_inode_xattr_getsuffix (void)
{
return NULL ;
diff --git a/mm/filemap.c b/mm/filemap.c
index c0774b5..915fd04 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1647,12 +1647,18 @@ int __remove_suid(struct dentry *dentry, int kill)

int remove_suid(struct dentry *dentry)
{
- int kill = should_remove_suid(dentry);
+ int killsuid = should_remove_suid(dentry);
+ int killpriv = security_inode_need_killpriv(dentry);
+ int error = 0;

- if (unlikely(kill))
- return __remove_suid(dentry, kill);
+ if (killpriv < 0)
+ return killpriv;
+ if (killpriv)
+ error = security_inode_killpriv(dentry);
+ if (!error && killsuid)
+ error = __remove_suid(dentry, killsuid);

- return 0;
+ return error;
}
EXPORT_SYMBOL(remove_suid);

diff --git a/security/capability.c b/security/capability.c
index dc2b66c..9e99f36 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -37,6 +37,8 @@ static struct security_operations capability_ops = {

.inode_setxattr = cap_inode_setxattr,
.inode_removexattr = cap_inode_removexattr,
+ .inode_need_killpriv = cap_inode_need_killpriv,
+ .inode_killpriv = cap_inode_killpriv,

.task_kill = cap_task_kill,
.task_setscheduler = cap_task_setscheduler,
diff --git a/security/commoncap.c b/security/commoncap.c
index aa6d929..7816cdc 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -119,6 +119,30 @@ static inline void bprm_clear_caps(struct linux_binprm *bprm)

#ifdef CONFIG_SECURITY_FILE_CAPABILITIES

+int cap_inode_need_killpriv(struct dentry *dentry)
+{
+ struct inode *inode = dentry->d_inode;
+ int error;
+
+ if (!inode->i_op || !inode->i_op->getxattr)
+ return 0;
+
+ error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
+ if (error <= 0)
+ return 0;
+ return 1;
+}
+
+int cap_inode_killpriv(struct dentry *dentry)
+{
+ struct inode *inode = dentry->d_inode;
+
+ if (!inode->i_op || !inode->i_op->removexattr)
+ return 0;
+
+ return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
+}
+
static inline int cap_from_disk(__le32 *caps, struct linux_binprm *bprm,
int size)
{
@@ -185,6 +209,16 @@ out:
}

#else
+int cap_inode_need_killpriv(struct dentry *dentry)
+{
+ return 0;
+}
+
+int cap_inode_killpriv(struct dentry *dentry)
+{
+ return 0;
+}
+
static inline int get_file_caps(struct linux_binprm *bprm)
{
bprm_clear_caps(bprm);
@@ -509,6 +543,7 @@ EXPORT_SYMBOL(cap_bprm_apply_creds);
EXPORT_SYMBOL(cap_bprm_secureexec);
EXPORT_SYMBOL(cap_inode_setxattr);
EXPORT_SYMBOL(cap_inode_removexattr);
+EXPORT_SYMBOL(cap_inode_killpriv);
EXPORT_SYMBOL(cap_task_post_setuid);
EXPORT_SYMBOL(cap_task_kill);
EXPORT_SYMBOL(cap_task_setscheduler);
diff --git a/security/dummy.c b/security/dummy.c
index 2d17040..5839faa 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -376,6 +376,16 @@ static int dummy_inode_removexattr (struct dentry *dentry, char *name)
return 0;
}

+static int dummy_inode_need_killpriv(struct dentry *dentry)
+{
+ return 0;
+}
+
+static int dummy_inode_killpriv(struct dentry *dentry)
+{
+ return 0;
+}
+
static int dummy_inode_getsecurity(const struct inode *inode, const char *name, void *buffer, size_t size, int err)
{
return -EOPNOTSUPP;
@@ -1017,6 +1027,8 @@ void security_fixup_ops (struct security_operations *ops)
set_to_dummy_if_null(ops, inode_getxattr);
set_to_dummy_if_null(ops, inode_listxattr);
set_to_dummy_if_null(ops, inode_removexattr);
+ set_to_dummy_if_null(ops, inode_need_killpriv);
+ set_to_dummy_if_null(ops, inode_killpriv);
set_to_dummy_if_null(ops, inode_xattr_getsuffix);
set_to_dummy_if_null(ops, inode_getsecurity);
set_to_dummy_if_null(ops, inode_setsecurity);
diff --git a/security/security.c b/security/security.c
index ebd71ad..335e1e1 100644
--- a/security/security.c
+++ b/security/security.c
@@ -515,6 +515,16 @@ int security_inode_removexattr(struct dentry *dentry, char *name)
return security_ops->inode_removexattr(dentry, name);
}

+int security_inode_need_killpriv(struct dentry *dentry)
+{
+ return security_ops->inode_need_killpriv(dentry);
+}
+
+int security_inode_killpriv(struct dentry *dentry)
+{
+ return security_ops->inode_killpriv(dentry);
+}
+
const char *security_inode_xattr_getsuffix(void)
{
return security_ops->inode_xattr_getsuffix();
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 8df2c17..c49b514 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2453,6 +2453,16 @@ static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t
return len;
}

+static int selinux_inode_need_killpriv(struct dentry *dentry)
+{
+ return secondary_ops->inode_need_killpriv(dentry);
+}
+
+static int selinux_inode_killpriv(struct dentry *dentry)
+{
+ return secondary_ops->inode_killpriv(dentry);
+}
+
/* file security operations */

static int selinux_file_permission(struct file *file, int mask)
@@ -4781,6 +4791,8 @@ static struct security_operations selinux_ops = {
.inode_getsecurity = selinux_inode_getsecurity,
.inode_setsecurity = selinux_inode_setsecurity,
.inode_listsecurity = selinux_inode_listsecurity,
+ .inode_need_killpriv = selinux_inode_need_killpriv,
+ .inode_killpriv = selinux_inode_killpriv,

.file_permission = selinux_file_permission,
.file_alloc_security = selinux_file_alloc_security,
--
1.5.1.1.GIT

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Next message: Henrique de Moraes Holschuh: "Re: Disk spin down issue on shut down/suspend to disk"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]