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[PATCH 9/9] userns: check user namespace for task->file uid equivalence checks [message #41745 is a reply to message #41743]

Thu, 17 February 2011 15:04

serge
Messages: 72
Registered: January 2007

Member

Cheat for now and say all files belong to init_user_ns. Next
step will be to let superblocks belong to a user_ns, and derive
inode_userns(inode) from inode->i_sb->s_user_ns. Finally we'll
introduce more flexible arrangements.

Changelog:
Feb 15: make is_owner_or_cap take const struct inode

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
---
fs/inode.c | 17 +++++++++++++++++
fs/namei.c | 20 +++++++++++++++-----
include/linux/fs.h | 9 +++++++--
3 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index da85e56..1930b45 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -25,6 +25,7 @@
#include <linux/async.h>
#include <linux/posix_acl.h>
#include <linux/ima.h>
+#include <linux/cred.h>

/*
* This is needed for the following functions:
@@ -1722,3 +1723,19 @@ void inode_init_owner(struct inode *inode, const struct inode *dir,
inode->i_mode = mode;
}
EXPORT_SYMBOL(inode_init_owner);
+
+/*
+ * return 1 if current either has CAP_FOWNER to the
+ * file, or owns the file.
+ */
+int is_owner_or_cap(const struct inode *inode)
+{
+ struct user_namespace *ns = inode_userns(inode);
+
+ if (current_user_ns() == ns && current_fsuid() == inode->i_uid)
+ return 1;
+ if (ns_capable(ns, CAP_FOWNER))
+ return 1;
+ return 0;
+}
+EXPORT_SYMBOL(is_owner_or_cap);
diff --git a/fs/namei.c b/fs/namei.c
index 9e701e2..cfac5b4 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -176,6 +176,9 @@ static int acl_permission_check(struct inode *inode, int mask, unsigned int flag

mask &= MAY_READ | MAY_WRITE | MAY_EXEC;

+ if (current_user_ns() != inode_userns(inode))
+ goto other_perms;
+
if (current_fsuid() == inode->i_uid)
mode >>= 6;
else {
@@ -189,6 +192,7 @@ static int acl_permission_check(struct inode *inode, int mask, unsigned int flag
mode >>= 3;
}

+other_perms:
/*
* If the DACs are ok we don't need any capability check.
*/
@@ -230,7 +234,7 @@ int generic_permission(struct inode *inode, int mask, unsigned int flags,
* Executable DACs are overridable if at least one exec bit is set.
*/
if (!(mask & MAY_EXEC) || execute_ok(inode))
- if (capable(CAP_DAC_OVERRIDE))
+ if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
return 0;

/*
@@ -238,7 +242,7 @@ int generic_permission(struct inode *inode, int mask, unsigned int flags,
*/
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
- if (capable(CAP_DAC_READ_SEARCH))
+ if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
return 0;

return -EACCES;
@@ -675,6 +679,7 @@ force_reval_path(struct path *path, struct nameidata *nd)
static inline int exec_permission(struct inode *inode, unsigned int flags)
{
int ret;
+ struct user_namespace *ns = inode_userns(inode);

if (inode->i_op->permission) {
ret = inode->i_op->permission(inode, MAY_EXEC, flags);
@@ -687,7 +692,7 @@ static inline int exec_permission(struct inode *inode, unsigned int flags)
if (ret == -ECHILD)
return ret;

- if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
+ if (ns_capable(ns, CAP_DAC_OVERRIDE) || ns_capable(ns, CAP_DAC_READ_SEARCH))
goto ok;

return ret;
@@ -1940,11 +1945,15 @@ static inline int check_sticky(struct inode *dir, struct inode *inode)

if (!(dir->i_mode & S_ISVTX))
return 0;
+ if (current_user_ns() != inode_userns(inode))
+ goto other_userns;
if (inode->i_uid == fsuid)
return 0;
if (dir->i_uid == fsuid)
return 0;
- return !capable(CAP_FOWNER);
+
+other_userns:
+ return !ns_capable(inode_userns(inode), CAP_FOWNER);
}

/*
@@ -2635,7 +2644,8 @@ int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
if (error)
return error;

- if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
+ if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
+ !ns_capable(inode_userns(dir), CAP_MKNOD))
return -EPERM;

if (!dir->i_op->mknod)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index bd32159..c84417a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1446,8 +1446,13 @@ enum {
#define put_fs_excl() atomic_dec(&current->fs_excl)
#define has_fs_excl() atomic_read(&current->fs_excl)

-#define is_owner_or_cap(inode) \
- ((current_fsuid() == (inode)->i_uid) || capable(CAP_FOWNER))
+/*
+ * until VFS tracks user namespaces for inodes, just make all files
+ * belong to init_user_ns
+ */
+extern struct user_namespace init_user_ns;
+#define inode_userns(inode) (&init_user_ns)
+extern int is_owner_or_cap(const struct inode *inode);

/* not quite ready to be deprecated, but... */
extern void lock_super(struct super_block *);
--
1.7.0.4

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[Message index]

		userns: targeted capabilities v5 By: serge on Thu, 17 February 2011 15:02
		[PATCH 2/9] security: Make capabilities relative to the user namespace. By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: ebiederm on Fri, 18 February 2011 03:46
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: Daniel Lezcano on Fri, 18 February 2011 23:44
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: David Howells on Wed, 23 February 2011 12:01
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: serge on Wed, 23 February 2011 13:43
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: David Howells on Wed, 23 February 2011 11:40
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: David Howells on Wed, 23 February 2011 16:59
		[PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: serge on Thu, 17 February 2011 15:04
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: ebiederm on Fri, 18 February 2011 01:29
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: serge on Thu, 24 February 2011 03:24
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: akpm on Thu, 24 February 2011 05:08
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: Daniel Lezcano on Sat, 19 February 2011 19:22
		[PATCH 7/9] add a user namespace owner of ipc ns By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 7/9] add a user namespace owner of ipc ns By: ebiederm on Fri, 18 February 2011 03:19
		Re: [PATCH 7/9] add a user namespace owner of ipc ns By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 7/9] add a user namespace owner of ipc ns By: Daniel Lezcano on Sat, 19 February 2011 17:57
		[PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: serge on Thu, 17 February 2011 15:02
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: ebiederm on Fri, 18 February 2011 03:31
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: Daniel Lezcano on Fri, 18 February 2011 16:57
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: David Howells on Wed, 23 February 2011 17:16
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: ebiederm on Wed, 23 February 2011 21:21
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: David Howells on Wed, 23 February 2011 23:19
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: ebiederm on Wed, 23 February 2011 23:54
		[PATCH 3/9] allow sethostname in a container By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 3/9] allow sethostname in a container By: ebiederm on Fri, 18 February 2011 03:05
		Re: [PATCH 3/9] allow sethostname in a container By: Daniel Lezcano on Fri, 18 February 2011 23:46
		[PATCH 4/9] allow killing tasks in your own or child userns By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: ebiederm on Fri, 18 February 2011 03:00
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: serge on Thu, 24 February 2011 00:48
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: akpm on Thu, 24 February 2011 00:54
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: Daniel Lezcano on Sat, 19 February 2011 10:55
		[PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: ebiederm on Fri, 18 February 2011 01:57
		Re: [PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: akpm on Sat, 19 February 2011 00:01
		Re: [PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: Daniel Lezcano on Sat, 19 February 2011 17:52
		[PATCH 5/9] Allow ptrace from non-init user namespaces By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: ebiederm on Fri, 18 February 2011 02:59
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: serge on Fri, 18 February 2011 04:36
		[PATCH] userns: ptrace: incorporate feedback from Eric By: serge on Thu, 24 February 2011 00:49
		Re: [PATCH] userns: ptrace: incorporate feedback from Eric By: akpm on Thu, 24 February 2011 00:56
		Re: [PATCH] userns: ptrace: incorporate feedback from Eric By: serge on Thu, 24 February 2011 03:15
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: serge on Thu, 24 February 2011 00:43
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: Daniel Lezcano on Sat, 19 February 2011 17:49
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: David Howells on Wed, 23 February 2011 17:05
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: David Howells on Wed, 23 February 2011 17:11
		[PATCH 8/9] user namespaces: convert several capable() calls By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 8/9] user namespaces: convert several capable() calls By: ebiederm on Fri, 18 February 2011 01:51
		Re: [PATCH 8/9] user namespaces: convert several capable() calls By: Daniel Lezcano on Sat, 19 February 2011 19:07
		Re: userns: targeted capabilities v5 By: akpm on Fri, 18 February 2011 00:21
		Re: userns: targeted capabilities v5 By: ebiederm on Fri, 18 February 2011 03:53
		Re: userns: targeted capabilities v5 By: serge on Fri, 18 February 2011 04:28
		User namespaces and keys By: David Howells on Wed, 23 February 2011 12:05
		Re: User namespaces and keys By: serge on Wed, 23 February 2011 13:58
		Re: User namespaces and keys By: ebiederm on Wed, 23 February 2011 14:46
		Re: User namespaces and keys By: David Howells on Wed, 23 February 2011 15:06
		Re: User namespaces and keys By: ebiederm on Wed, 23 February 2011 15:45
		Re: User namespaces and keys By: Serge E. Hallyn on Wed, 23 February 2011 15:53
		Re: User namespaces and keys By: Casey Schaufler on Wed, 23 February 2011 19:24
		Re: User namespaces and keys By: ebiederm on Wed, 23 February 2011 20:55
		Re: User namespaces and keys By: Casey Schaufler on Wed, 23 February 2011 21:37
		Re: User namespaces and keys By: ebiederm on Thu, 24 February 2011 06:56

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