linux-kernel - Re: [PATCH] hfsplus: Fix bug causing custom uid and gid being unable to be assigned with mount

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Message-Id: <55A80630-60FB-44BE-9628-29104AB8A7D0@dubeyko.com>
Date:   Fri, 2 Dec 2022 12:52:05 -0800
From:   Viacheslav Dubeyko <slava@...eyko.com>
To:     Aditya Garg <gargaditya08@...e.com>
Cc:     "willy@...radead.org" <willy@...radead.org>,
        "ira.weiny@...el.com" <ira.weiny@...el.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "bvanassche@....org" <bvanassche@....org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "songmuchun@...edance.com" <songmuchun@...edance.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] hfsplus: Fix bug causing custom uid and gid being unable
 to be assigned with mount



> On Dec 2, 2022, at 7:39 AM, Aditya Garg <gargaditya08@...e.com> wrote:
> 
> From: Aditya Garg <gargaditya08@...e.com>
> 
> Inspite of specifying UID and GID in mount command, the specified UID and
> GID was not being assigned. This patch fixes this issue.
> 
> Signed-off-by: Aditya Garg <gargaditya08@...e.com>
> ---
> fs/hfsplus/hfsplus_fs.h | 2 ++
> fs/hfsplus/inode.c      | 4 ++--
> fs/hfsplus/options.c    | 2 ++
> 3 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
> index a5db2e3b2..6aa919e59 100644
> --- a/fs/hfsplus/hfsplus_fs.h
> +++ b/fs/hfsplus/hfsplus_fs.h
> @@ -198,6 +198,8 @@ struct hfsplus_sb_info {
> #define HFSPLUS_SB_HFSX		3
> #define HFSPLUS_SB_CASEFOLD	4
> #define HFSPLUS_SB_NOBARRIER	5
> +#define HFSPLUS_SB_UID		6
> +#define HFSPLUS_SB_GID		7
> 
> static inline struct hfsplus_sb_info *HFSPLUS_SB(struct super_block *sb)
> {
> diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
> index aeab83ed1..4d1077db8 100644
> --- a/fs/hfsplus/inode.c
> +++ b/fs/hfsplus/inode.c
> @@ -192,11 +192,11 @@ static void hfsplus_get_perms(struct inode *inode,
> 	mode = be16_to_cpu(perms->mode);
> 
> 	i_uid_write(inode, be32_to_cpu(perms->owner));
> -	if (!i_uid_read(inode) && !mode)
> +	if (test_bit(HFSPLUS_SB_UID, &sbi->flags))
> 		inode->i_uid = sbi->uid;
> 
> 	i_gid_write(inode, be32_to_cpu(perms->group));
> -	if (!i_gid_read(inode) && !mode)
> +	if (test_bit(HFSPLUS_SB_GID, &sbi->flags))
> 		inode->i_gid = sbi->gid;

I am slightly confused. Do you mean that all files/folders will have the same UID/GID always?
What if user changes the UID/GID a particular file/folder? Also, what if we mounted
file system without specifying the UID/GID, then what UID/GID will be returned by
your logic?

Thanks,
Slava.

> 
> 	if (dir) {
> diff --git a/fs/hfsplus/options.c b/fs/hfsplus/options.c
> index 047e05c57..10a0bdacb 100644
> --- a/fs/hfsplus/options.c
> +++ b/fs/hfsplus/options.c
> @@ -137,6 +137,7 @@ int hfsplus_parse_options(char *input, struct hfsplus_sb_info *sbi)
> 				return 0;
> 			}
> 			sbi->uid = make_kuid(current_user_ns(), (uid_t)tmp);
> +			set_bit(HFSPLUS_SB_UID, &sbi->flags);
> 			if (!uid_valid(sbi->uid)) {
> 				pr_err("invalid uid specified\n");
> 				return 0;
> @@ -148,6 +149,7 @@ int hfsplus_parse_options(char *input, struct hfsplus_sb_info *sbi)
> 				return 0;
> 			}
> 			sbi->gid = make_kgid(current_user_ns(), (gid_t)tmp);
> +			set_bit(HFSPLUS_SB_GID, &sbi->flags);
> 			if (!gid_valid(sbi->gid)) {
> 				pr_err("invalid gid specified\n");
> 				return 0;
> -- 
> 2.38.1
>