On Fri, 16 Dec 2011 12:25:34 +0100
Djalal Harouni <tixxdz@xxxxxxxxxx> wrote:
>
> Calls to notify_change() must hold i_mutex.
>
It seems that this is true. It's tersely documented in
Documentation/filesystems/porting. It should be mentioned in the
non-existent notify_change() kerneldoc.
<does a quick audit>
fs/hpfs/namei.c and fs/nfsd/vfs.c:nfsd_setattr() aren't obviosuly
holding that lock when calling notify_change(). Everything else under
fs/ looks OK.
I'll add the below to my tree and shall slip it into linux-next, but not
mainline:
--- a/fs/attr.c~a
+++ a/fs/attr.c
@@ -171,6 +171,8 @@ int notify_change(struct dentry * dentry
struct timespec now;
unsigned int ia_valid = attr->ia_valid;
+ WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
+
if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
return -EPERM;
@@ -245,5 +247,4 @@ int notify_change(struct dentry * dentry
return error;
}
-
EXPORT_SYMBOL(notify_change);
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1994,10 +1994,16 @@ EXPORT_SYMBOL(should_remove_suid);
>
> static int __remove_suid(struct dentry *dentry, int kill)
> {
> + int ret;
> struct iattr newattrs;
>
> newattrs.ia_valid = ATTR_FORCE | kill;
> - return notify_change(dentry, &newattrs);
> +
> + mutex_lock(&dentry->d_inode->i_mutex);
> + ret = notify_change(dentry, &newattrs);
> + mutex_unlock(&dentry->d_inode->i_mutex);
> +
> + return ret;
> }
>
> int file_remove_suid(struct file *file)
Looks good to me.
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