[PATCH 16/30] r/o bind mounts: elevate write count for do_utimes()

Dave Hansen
2008-02-15T22:46:13Z

Now includes fix for oops seen by akpm.

"never let a libc developer write your kernel code" - hch

"nor, apparently, a kernel developer" - akpm

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

linux-2.6.git-dave/fs/utimes.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

diff -puN fs/utimes.c~r-o-bind-mounts-elevate-write-count-for-do_utimes fs/utimes.c
--- linux-2.6.git/fs/utimes.c~r-o-bind-mounts-elevate-write-count-for-do_utimes 2008-02-15 13:25:50.000000000 -0800
+++ linux-2.6.git-dave/fs/utimes.c 2008-02-15 13:25:50.000000000 -0800
@@ -2,6 +2,7 @@
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/linkage.h>
+#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/sched.h>
#include <linux/stat.h>
@@ -59,6 +60,7 @@ long do_utimes(int dfd, char __user *fil
struct inode *inode;
struct iattr newattrs;
struct file *f = NULL;
+ struct vfsmount *mnt;

error = -EINVAL;
if (times && (!nsec_valid(times[0].tv_nsec) ||
@@ -79,18 +81,20 @@ long do_utimes(int dfd, char __user *fil
if (!f)
goto out;
dentry = f->f_path.dentry;
+ mnt = f->f_path.mnt;
} else {
error = __user_walk_fd(dfd, filename, (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW, &nd);
if (error)
goto out;

dentry = nd.path.dentry;
+ mnt = nd.path.mnt;
}

inode = dentry->d_inode;

- error = -EROFS;
- if (IS_RDONLY(inode))
+ error = mnt_want_write(mnt);
+ if (error)
goto dput_and_out;

/* Don't worry, the checks are done in inode_change_ok() */
@@ -98,7 +102,7 @@ long do_utimes(int dfd, char __user *fil
if (times) {
error = -EPERM;
if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
- goto dput_and_out;
+ goto mnt_drop_write_and_out;

if (times[0].tv_nsec == UTIME_OMIT)
newattrs.ia_valid &= ~ATTR_ATIME;
@@ -118,22 +122,24 @@ long do_utimes(int dfd, char __user *fil
} else {
error = -EACCES;
if (IS_IMMUTABLE(inode))
- goto dput_and_out;
+ goto mnt_drop_write_and_out;

if (!is_owner_or_cap(inode)) {
if (f) {
if (!(f->f_mode & FMODE_WRITE))
- goto dput_and_out;
+ goto mnt_drop_write_and_out;
} else {
error = vfs_permission(&nd, MAY_WRITE);
if (error)
- goto dput_and_out;
+ goto mnt_drop_write_and_out;
}
}
}
mutex_lock(&inode->i_mutex);
error = notify_change(dentry, &newattrs);
mutex_unlock(&inode->i_mutex);
+mnt_drop_write_and_out:
+ mnt_drop_write(mnt);
dput_and_out:
if (f)
fput(f);
_