android_kernel_google_msm/fs/utimes.c
Satyam Sharma 3bd858ab1c Introduce is_owner_or_cap() to wrap CAP_FOWNER use with fsuid check
Introduce is_owner_or_cap() macro in fs.h, and convert over relevant
users to it. This is done because we want to avoid bugs in the future
where we check for only effective fsuid of the current task against a
file's owning uid, without simultaneously checking for CAP_FOWNER as
well, thus violating its semantics.
[ XFS uses special macros and structures, and in general looked ...
untouchable, so we leave it alone -- but it has been looked over. ]

The (current->fsuid != inode->i_uid) check in generic_permission() and
exec_permission_lite() is left alone, because those operations are
covered by CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH. Similarly operations
falling under the purview of CAP_CHOWN and CAP_LEASE are also left alone.

Signed-off-by: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Cc: Al Viro <viro@ftp.linux.org.uk>
Acked-by: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17 12:00:03 -07:00

187 lines
4.8 KiB
C

#include <linux/compiler.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/linkage.h>
#include <linux/namei.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/utime.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#ifdef __ARCH_WANT_SYS_UTIME
/*
* sys_utime() can be implemented in user-level using sys_utimes().
* Is this for backwards compatibility? If so, why not move it
* into the appropriate arch directory (for those architectures that
* need it).
*/
/* If times==NULL, set access and modification to current time,
* must be owner or have write permission.
* Else, update from *times, must be owner or super user.
*/
asmlinkage long sys_utime(char __user *filename, struct utimbuf __user *times)
{
struct timespec tv[2];
if (times) {
if (get_user(tv[0].tv_sec, &times->actime) ||
get_user(tv[1].tv_sec, &times->modtime))
return -EFAULT;
tv[0].tv_nsec = 0;
tv[1].tv_nsec = 0;
}
return do_utimes(AT_FDCWD, filename, times ? tv : NULL, 0);
}
#endif
/* If times==NULL, set access and modification to current time,
* must be owner or have write permission.
* Else, update from *times, must be owner or super user.
*/
long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags)
{
int error;
struct nameidata nd;
struct dentry *dentry;
struct inode *inode;
struct iattr newattrs;
struct file *f = NULL;
error = -EINVAL;
if (flags & ~AT_SYMLINK_NOFOLLOW)
goto out;
if (filename == NULL && dfd != AT_FDCWD) {
error = -EINVAL;
if (flags & AT_SYMLINK_NOFOLLOW)
goto out;
error = -EBADF;
f = fget(dfd);
if (!f)
goto out;
dentry = f->f_path.dentry;
} else {
error = __user_walk_fd(dfd, filename, (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW, &nd);
if (error)
goto out;
dentry = nd.dentry;
}
inode = dentry->d_inode;
error = -EROFS;
if (IS_RDONLY(inode))
goto dput_and_out;
/* Don't worry, the checks are done in inode_change_ok() */
newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
if (times) {
error = -EPERM;
if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
goto dput_and_out;
if (times[0].tv_nsec == UTIME_OMIT)
newattrs.ia_valid &= ~ATTR_ATIME;
else if (times[0].tv_nsec != UTIME_NOW) {
newattrs.ia_atime.tv_sec = times[0].tv_sec;
newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
newattrs.ia_valid |= ATTR_ATIME_SET;
}
if (times[1].tv_nsec == UTIME_OMIT)
newattrs.ia_valid &= ~ATTR_MTIME;
else if (times[1].tv_nsec != UTIME_NOW) {
newattrs.ia_mtime.tv_sec = times[1].tv_sec;
newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
newattrs.ia_valid |= ATTR_MTIME_SET;
}
} else {
error = -EACCES;
if (IS_IMMUTABLE(inode))
goto dput_and_out;
if (!is_owner_or_cap(inode)) {
if (f) {
if (!(f->f_mode & FMODE_WRITE))
goto dput_and_out;
} else {
error = vfs_permission(&nd, MAY_WRITE);
if (error)
goto dput_and_out;
}
}
}
mutex_lock(&inode->i_mutex);
error = notify_change(dentry, &newattrs);
mutex_unlock(&inode->i_mutex);
dput_and_out:
if (f)
fput(f);
else
path_release(&nd);
out:
return error;
}
asmlinkage long sys_utimensat(int dfd, char __user *filename, struct timespec __user *utimes, int flags)
{
struct timespec tstimes[2];
if (utimes) {
if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
return -EFAULT;
if ((tstimes[0].tv_nsec == UTIME_OMIT ||
tstimes[0].tv_nsec == UTIME_NOW) &&
tstimes[0].tv_sec != 0)
return -EINVAL;
if ((tstimes[1].tv_nsec == UTIME_OMIT ||
tstimes[1].tv_nsec == UTIME_NOW) &&
tstimes[1].tv_sec != 0)
return -EINVAL;
/* Nothing to do, we must not even check the path. */
if (tstimes[0].tv_nsec == UTIME_OMIT &&
tstimes[1].tv_nsec == UTIME_OMIT)
return 0;
}
return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
}
asmlinkage long sys_futimesat(int dfd, char __user *filename, struct timeval __user *utimes)
{
struct timeval times[2];
struct timespec tstimes[2];
if (utimes) {
if (copy_from_user(&times, utimes, sizeof(times)))
return -EFAULT;
/* This test is needed to catch all invalid values. If we
would test only in do_utimes we would miss those invalid
values truncated by the multiplication with 1000. Note
that we also catch UTIME_{NOW,OMIT} here which are only
valid for utimensat. */
if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
return -EINVAL;
tstimes[0].tv_sec = times[0].tv_sec;
tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
tstimes[1].tv_sec = times[1].tv_sec;
tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
}
return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
}
asmlinkage long sys_utimes(char __user *filename, struct timeval __user *utimes)
{
return sys_futimesat(AT_FDCWD, filename, utimes);
}