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Commit 935d8aab authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Add file_ns_capable() helper function for open-time capability checking 



Nothing is using it yet, but this will allow us to delay the open-time
checks to use time, without breaking the normal UNIX permission
semantics where permissions are determined by the opener (and the file
descriptor can then be passed to a different process, or the process can
drop capabilities).

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5b55d708

include/linux/capability.h

+2 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ struct cpu_vfs_cap_data { 
#define _KERNEL_CAP_T_SIZE     (sizeof(kernel_cap_t))





struct file;

struct inode;

struct dentry;

struct user_namespace;
@@ -211,6 +212,7 @@ extern bool capable(int cap); 
extern bool ns_capable(struct user_namespace *ns, int cap);

extern bool nsown_capable(int cap);

extern bool inode_capable(const struct inode *inode, int cap);

extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);



/* audit system wants to get cap info from files as well */

extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);

kernel/capability.c

+24 −0
Original line number Diff line number Diff line
@@ -392,6 +392,30 @@ bool ns_capable(struct user_namespace *ns, int cap) 
}

EXPORT_SYMBOL(ns_capable);



/**

 * file_ns_capable - Determine if the file's opener had a capability in effect

 * @file:  The file we want to check

 * @ns:  The usernamespace we want the capability in

 * @cap: The capability to be tested for

 *

 * Return true if task that opened the file had a capability in effect

 * when the file was opened.

 *

 * This does not set PF_SUPERPRIV because the caller may not

 * actually be privileged.

 */

bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap)

{

	if (WARN_ON_ONCE(!cap_valid(cap)))

		return false;



	if (security_capable(file->f_cred, ns, cap) == 0)

		return true;



	return false;

}

EXPORT_SYMBOL(file_ns_capable);



/**

 * capable - Determine if the current task has a superior capability in effect

 * @cap: The capability to be tested for