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fix open/umount race

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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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6
fs/open.c
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@@ -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;
}