[v2] exfat: zero the reserved fields of file and stream extension dentries

Commit Message

[e-mail] April 25, 2024, 4:55 a.m. UTC

From exFAT specification, the reserved fields should initialize
to zero and should not use for any purpose.

If create a new dentry set in the UNUSED dentries, all fields
had been zeroed when allocating cluster to parent directory.

But if create a new dentry set in the DELETED dentries, the
reserved fields in file and stream extension dentries may be
non-zero. Because only the valid bit of the type field of the
dentry is cleared in exfat_remove_entries(), if the type of
dentry is different from the original(For example, a dentry that
was originally a file name dentry, then set to deleted dentry,
and then set as a file dentry), the reserved fields is non-zero.

So this commit initializes the dentry to 0 before createing file
dentry and stream extension dentry.

Signed-off-by: Yuezhang Mo <[e-mail]>
Reviewed-by: Andy Wu <[e-mail]>
Reviewed-by: Aoyama Wataru <[e-mail]>
---
 fs/exfat/dir.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Sungjong Seo April 25, 2024, 6:15 a.m. UTC | #1

> From exFAT specification, the reserved fields should initialize
> to zero and should not use for any purpose.
> 
> If create a new dentry set in the UNUSED dentries, all fields
> had been zeroed when allocating cluster to parent directory.
> 
> But if create a new dentry set in the DELETED dentries, the
> reserved fields in file and stream extension dentries may be
> non-zero. Because only the valid bit of the type field of the
> dentry is cleared in exfat_remove_entries(), if the type of
> dentry is different from the original(For example, a dentry that
> was originally a file name dentry, then set to deleted dentry,
> and then set as a file dentry), the reserved fields is non-zero.
> 
> So this commit initializes the dentry to 0 before createing file
> dentry and stream extension dentry.
> 
> Signed-off-by: Yuezhang Mo <[e-mail]>
> Reviewed-by: Andy Wu <[e-mail]>
> Reviewed-by: Aoyama Wataru <[e-mail]>

Looks good. Thanks for your patch.
Reviewed-by: Sungjong Seo <[e-mail]>

> ---
>  fs/exfat/dir.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
> index 077944d3c2c0..84572e11cc05 100644
> --- a/fs/exfat/dir.c
> +++ b/fs/exfat/dir.c
> @@ -420,6 +420,7 @@ static void exfat_set_entry_type(struct exfat_dentry
> *ep, unsigned int type)
>  static void exfat_init_stream_entry(struct exfat_dentry *ep,
>  		unsigned int start_clu, unsigned long long size)
>  {
> +	memset(ep, 0, sizeof(*ep));
>  	exfat_set_entry_type(ep, TYPE_STREAM);
>  	if (size == 0)
>  		ep->dentry.stream.flags = ALLOC_FAT_CHAIN;
> @@ -457,6 +458,7 @@ void exfat_init_dir_entry(struct exfat_entry_set_cache
> *es,
>  	struct exfat_dentry *ep;
> 
>  	ep = exfat_get_dentry_cached(es, ES_IDX_FILE);
> +	memset(ep, 0, sizeof(*ep));
>  	exfat_set_entry_type(ep, type);
>  	exfat_set_entry_time(sbi, ts,
>  			&ep->dentry.file.create_tz,
> --
> 2.34.1

Namjae Jeon April 25, 2024, 1:05 p.m. UTC | #2

2024년 4월 25일 (목) 오후 3:23, Sungjong Seo <[e-mail]>님이 작성:
>
> > From exFAT specification, the reserved fields should initialize
> > to zero and should not use for any purpose.
> >
> > If create a new dentry set in the UNUSED dentries, all fields
> > had been zeroed when allocating cluster to parent directory.
> >
> > But if create a new dentry set in the DELETED dentries, the
> > reserved fields in file and stream extension dentries may be
> > non-zero. Because only the valid bit of the type field of the
> > dentry is cleared in exfat_remove_entries(), if the type of
> > dentry is different from the original(For example, a dentry that
> > was originally a file name dentry, then set to deleted dentry,
> > and then set as a file dentry), the reserved fields is non-zero.
> >
> > So this commit initializes the dentry to 0 before createing file
> > dentry and stream extension dentry.
> >
> > Signed-off-by: Yuezhang Mo <[e-mail]>
> > Reviewed-by: Andy Wu <[e-mail]>
> > Reviewed-by: Aoyama Wataru <[e-mail]>
>
> Looks good. Thanks for your patch.
> Reviewed-by: Sungjong Seo <[e-mail]>
Applied it to #dev.
Thanks!

Patch

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index 077944d3c2c0..84572e11cc05 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -420,6 +420,7 @@  static void exfat_set_entry_type(struct exfat_dentry *ep, unsigned int type)
 static void exfat_init_stream_entry(struct exfat_dentry *ep,
 		unsigned int start_clu, unsigned long long size)
 {
+	memset(ep, 0, sizeof(*ep));
 	exfat_set_entry_type(ep, TYPE_STREAM);
 	if (size == 0)
 		ep->dentry.stream.flags = ALLOC_FAT_CHAIN;
@@ -457,6 +458,7 @@  void exfat_init_dir_entry(struct exfat_entry_set_cache *es,
 	struct exfat_dentry *ep;
 
 	ep = exfat_get_dentry_cached(es, ES_IDX_FILE);
+	memset(ep, 0, sizeof(*ep));
 	exfat_set_entry_type(ep, type);
 	exfat_set_entry_time(sbi, ts,
 			&ep->dentry.file.create_tz,