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

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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>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Dave Hansen 2008-02-15 14:37:42 -08:00 committed by Al Viro
parent cdb70f3f74
commit 74f9fdfa1f
1 changed files with 12 additions and 6 deletions
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18
fs/utimes.c
View File

@ -2,6 +2,7 @@
#include <linux/file.h> #include <linux/file.h>
#include <linux/fs.h> #include <linux/fs.h>
#include <linux/linkage.h> #include <linux/linkage.h>
#include <linux/mount.h>
#include <linux/namei.h> #include <linux/namei.h>
#include <linux/sched.h> #include <linux/sched.h>
#include <linux/stat.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 inode *inode;
struct iattr newattrs; struct iattr newattrs;
struct file *f = NULL; struct file *f = NULL;
struct vfsmount *mnt;
error = -EINVAL; error = -EINVAL;
if (times && (!nsec_valid(times[0].tv_nsec) || 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) if (!f)
goto out; goto out;
dentry = f->f_path.dentry; dentry = f->f_path.dentry;
mnt = f->f_path.mnt;
} else { } else {
error = __user_walk_fd(dfd, filename, (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW, &nd); error = __user_walk_fd(dfd, filename, (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW, &nd);
if (error) if (error)
goto out; goto out;
dentry = nd.path.dentry; dentry = nd.path.dentry;
mnt = nd.path.mnt;
} }
inode = dentry->d_inode; inode = dentry->d_inode;
error = -EROFS; error = mnt_want_write(mnt);
if (IS_RDONLY(inode)) if (error)
goto dput_and_out; goto dput_and_out;
/* Don't worry, the checks are done in inode_change_ok() */ /* 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) { if (times) {
error = -EPERM; error = -EPERM;
if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
goto dput_and_out; goto mnt_drop_write_and_out;
if (times[0].tv_nsec == UTIME_OMIT) if (times[0].tv_nsec == UTIME_OMIT)
newattrs.ia_valid &= ~ATTR_ATIME; newattrs.ia_valid &= ~ATTR_ATIME;
@ -118,22 +122,24 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
} else { } else {
error = -EACCES; error = -EACCES;
if (IS_IMMUTABLE(inode)) if (IS_IMMUTABLE(inode))
goto dput_and_out; goto mnt_drop_write_and_out;
if (!is_owner_or_cap(inode)) { if (!is_owner_or_cap(inode)) {
if (f) { if (f) {
if (!(f->f_mode & FMODE_WRITE)) if (!(f->f_mode & FMODE_WRITE))
goto dput_and_out; goto mnt_drop_write_and_out;
} else { } else {
error = vfs_permission(&nd, MAY_WRITE); error = vfs_permission(&nd, MAY_WRITE);
if (error) if (error)
goto dput_and_out; goto mnt_drop_write_and_out;
} }
} }
} }
mutex_lock(&inode->i_mutex); mutex_lock(&inode->i_mutex);
error = notify_change(dentry, &newattrs); error = notify_change(dentry, &newattrs);
mutex_unlock(&inode->i_mutex); mutex_unlock(&inode->i_mutex);
mnt_drop_write_and_out:
mnt_drop_write(mnt);
dput_and_out: dput_and_out:
if (f) if (f)
fput(f); fput(f);