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linux-2.6
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fix open/umount race 

nameidata_to_filp() drops nd->path or transfers it to opened
file.  In the former case it's a Bad Idea(tm) to do mnt_drop_write()
on nd->path.mnt, since we might race with umount and vfsmount in
question might be gone already.

Fix: don't drop it, then...  IOW, have nameidata_to_filp() grab nd->path
in case it transfers it to file and do path_drop() in callers.  After
they are through with accessing nd->path...

Reported-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2010-10-29 03:30:42 -04:00
parent a4118ee1d8
commit d893f1bc2a
2 changed files with 5 additions and 3 deletions
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2
fs/namei.c
View File

@ -1574,6 +1574,7 @@ static struct file *finish_open(struct nameidata *nd,
*/
if (will_truncate)
mnt_drop_write(nd->path.mnt);
path_put(&nd->path);
return filp;
exit:
@ -1675,6 +1676,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
}
filp = nameidata_to_filp(nd);
mnt_drop_write(nd->path.mnt);
path_put(&nd->path);
if (!IS_ERR(filp)) {
error = ima_file_check(filp, acc_mode);
if (error) {

6
fs/open.c
View File

@ -786,11 +786,11 @@ struct file *nameidata_to_filp(struct nameidata *nd)
/* Pick up the filp from the open intent */
filp = nd->intent.open.file;
/* Has the filesystem initialised the file for us? */
if (filp->f_path.dentry == NULL)
if (filp->f_path.dentry == NULL) {
path_get(&nd->path);
filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
NULL, cred);
else
path_put(&nd->path);
}
return filp;
}