From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Al Viro brought it to my attention that the dentries may not be filled
when the parse_options() is called, causing the call to set_gid() to
possibly crash. It should only be called if parse_options() succeeds
totally anyway.

He suggested the logical place to do the update is in apply_options().

Link: https://lore.kernel.org/all/20220225165219.737025658@goodmis.org/

Cc: stable@vger.kernel.org
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 48b27b6b5191 ("tracefs: Set all files to the same group ownership as the mount option")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/inode.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index bafc02bf8220..3638d330ff5a 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -264,7 +264,6 @@ static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
 			if (!gid_valid(gid))
 				return -EINVAL;
 			opts->gid = gid;
-			set_gid(tracefs_mount->mnt_root, gid);
 			break;
 		case Opt_mode:
 			if (match_octal(&args[0], &option))
@@ -293,6 +292,9 @@ static int tracefs_apply_options(struct super_block *sb)
 	inode->i_uid = opts->uid;
 	inode->i_gid = opts->gid;
 
+	if (tracefs_mount && tracefs_mount->mnt_root)
+		set_gid(tracefs_mount->mnt_root, opts->gid);
+
 	return 0;
 }
 
-- 
2.34.1

On Fri, 25 Feb 2022 15:21:23 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> 
> Al Viro brought it to my attention that the dentries may not be filled
> when the parse_options() is called, causing the call to set_gid() to
> possibly crash. It should only be called if parse_options() succeeds
> totally anyway.
> 
> He suggested the logical place to do the update is in apply_options().
> 
> Link: https://lore.kernel.org/all/20220225165219.737025658@goodmis.org/
> 
> Cc: stable@vger.kernel.org
> Reported-by: Al Viro <viro@zeniv.linux.org.uk>
> Fixes: 48b27b6b5191 ("tracefs: Set all files to the same group ownership as the mount option")
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  fs/tracefs/inode.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
> index bafc02bf8220..3638d330ff5a 100644
> --- a/fs/tracefs/inode.c
> +++ b/fs/tracefs/inode.c
> @@ -264,7 +264,6 @@ static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
>  			if (!gid_valid(gid))
>  				return -EINVAL;
>  			opts->gid = gid;
> -			set_gid(tracefs_mount->mnt_root, gid);
>  			break;
>  		case Opt_mode:
>  			if (match_octal(&args[0], &option))
> @@ -293,6 +292,9 @@ static int tracefs_apply_options(struct super_block *sb)
>  	inode->i_uid = opts->uid;
>  	inode->i_gid = opts->gid;
>  
> +	if (tracefs_mount && tracefs_mount->mnt_root)
> +		set_gid(tracefs_mount->mnt_root, opts->gid);

Bah, I forgot the '-a' in 'git commit -a --amend'

Ignore this :-/

-- Steve

> +
>  	return 0;
>  }
>