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Commit 74f9fdfa authored by Dave Hansen's avatar Dave Hansen Committed by Al Viro
Browse files

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



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: default avatarAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: default avatarDave Hansen <haveblue@us.ibm.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent cdb70f3f

fs/utimes.c

+12 −6
Original line number Diff line number Diff line
@@ -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 *filename, struct timespec *times, int flags 
	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 *filename, struct timespec *times, int flags 
		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 *filename, struct timespec *times, int flags 
	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 *filename, struct timespec *times, int flags 
	} 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);