ntfs3: fix double free of sbi->options->nls and clarify ownership of fc->fs_private

[PATCH] [PATCH] ntfs3: fix double free of sbi->options->nls and clarify ownership of fc->fs_private

Posted by YangWen 3 months, 1 week ago

commit 02f312754c87 ("ntfs3: fix use-after-free of sbi->options in cmp_fnames") introduced a use-after-free bug
due to improper handling of sbi->options in error paths. This resulted in crashes when superblock cleanup
is performed in ntfs_put_super.

This patch ensures that the options structure and its subfields are properly freed, preventing the memory
corruption and use-after-free errors.

Reported-by: syzbot+cc433e4cd6d54736bf80@syzkaller.appspotmail.com
Signed-off-by: YangWen <anmuxixixi@gmail.com>
---
 fs/ntfs3/super.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index aae1f32f4dab..5d4ca4c10116 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -705,7 +705,7 @@ static void ntfs_put_super(struct super_block *sb)
 
 	if (sbi->options) {
 		unload_nls(sbi->options->nls);
-		kfree(sbi->options->nls);
+		kfree(sbi->options->nls_name);
 		kfree(sbi->options);
 		sbi->options = NULL;
 	}
@@ -1246,6 +1246,7 @@ static int ntfs_fill_super(struct super_block *sb, struct fs_context *fc)
 		}
 	}
 	sbi->options = options;
+	fc->fs_private = NULL;
 	sb->s_flags |= SB_NODIRATIME;
 	sb->s_magic = 0x7366746e; // "ntfs"
 	sb->s_op = &ntfs_sops;
@@ -1671,7 +1672,7 @@ static int ntfs_fill_super(struct super_block *sb, struct fs_context *fc)
 out:
 	if (sbi && sbi->options) {
 		unload_nls(sbi->options->nls);
-		kfree(sbi->options->nls);
+		kfree(sbi->options->nls_name);
 		kfree(sbi->options);
 		sbi->options = NULL;
 	}
-- 
2.43.0

Re: [PATCH] [PATCH] ntfs3: fix double free of sbi->options->nls and clarify ownership of fc->fs_private

Posted by Konstantin Komarov 2 months, 2 weeks ago

On 10/30/25 17:20, YangWen wrote:

> commit 02f312754c87 ("ntfs3: fix use-after-free of sbi->options in cmp_fnames") introduced a use-after-free bug
> due to improper handling of sbi->options in error paths. This resulted in crashes when superblock cleanup
> is performed in ntfs_put_super.
>
> This patch ensures that the options structure and its subfields are properly freed, preventing the memory
> corruption and use-after-free errors.
>
> Reported-by: syzbot+cc433e4cd6d54736bf80@syzkaller.appspotmail.com
> Signed-off-by: YangWen <anmuxixixi@gmail.com>
> ---
>   fs/ntfs3/super.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
> index aae1f32f4dab..5d4ca4c10116 100644
> --- a/fs/ntfs3/super.c
> +++ b/fs/ntfs3/super.c
> @@ -705,7 +705,7 @@ static void ntfs_put_super(struct super_block *sb)
>   
>   	if (sbi->options) {
>   		unload_nls(sbi->options->nls);
> -		kfree(sbi->options->nls);
> +		kfree(sbi->options->nls_name);
>   		kfree(sbi->options);
>   		sbi->options = NULL;
>   	}
> @@ -1246,6 +1246,7 @@ static int ntfs_fill_super(struct super_block *sb, struct fs_context *fc)
>   		}
>   	}
>   	sbi->options = options;
> +	fc->fs_private = NULL;
>   	sb->s_flags |= SB_NODIRATIME;
>   	sb->s_magic = 0x7366746e; // "ntfs"
>   	sb->s_op = &ntfs_sops;
> @@ -1671,7 +1672,7 @@ static int ntfs_fill_super(struct super_block *sb, struct fs_context *fc)
>   out:
>   	if (sbi && sbi->options) {
>   		unload_nls(sbi->options->nls);
> -		kfree(sbi->options->nls);
> +		kfree(sbi->options->nls_name);
>   		kfree(sbi->options);
>   		sbi->options = NULL;
>   	}

Applied to my tree with added "Fixes:" and "Closes:" tags, thanks for the
patch.

Regards,
Konstantin