linux-kernel - Re: [PATCH v2] sparse: fix incorrect fmode

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Date:   Wed, 18 May 2022 13:12:02 +0200
From:   Jan Kara <jack@...e.cz>
To:     Vasily Averin <vvs@...nvz.org>
Cc:     Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
        Christian Brauner <brauner@...nel.org>, kernel@...nvz.org,
        linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Amir Goldstein <amir73il@...il.com>,
        Matthew Bobrowski <repnop@...gle.com>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2] sparse: fix incorrect fmode_t casts

On Wed 18-05-22 13:49:07, Vasily Averin wrote:
> Fixes sparce warnings:
> fs/notify/fanotify/fanotify_user.c:267:63: sparse:
>  warning: restricted fmode_t degrades to integer
> fs/notify/fanotify/fanotify_user.c:1351:28: sparse:
>  warning: restricted fmode_t degrades to integer
> fs/proc/base.c:2240:25: sparse: warning: cast to restricted fmode_t
> fs/proc/base.c:2297:42: sparse: warning: cast from restricted fmode_t
> fs/proc/base.c:2394:48: sparse: warning: cast from restricted fmode_t
> fs/open.c:1024:21: sparse: warning: restricted fmode_t degrades to integer
> 
> Signed-off-by: Vasily Averin <vvs@...nvz.org>

Feel free to add:

Acked-by: Jan Kara <jack@...e.cz>

for the fanotify bits.

								Honza

> ---
> v2:
>  1) use __FMODE_NONOTIFY instead of FMODE_NONOTIFY
>  2) introduced fmode_instantiate_de/encode helpers
>       thanks Christoph Hellwig for the hints
> ---
>  fs/notify/fanotify/fanotify_user.c |  4 ++--
>  fs/open.c                          |  2 +-
>  fs/proc/base.c                     | 21 ++++++++++++++++-----
>  3 files changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 9b32b76a9c30..2bec3b612618 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -264,7 +264,7 @@ static int create_fd(struct fsnotify_group *group, struct path *path,
>  	 * originally opened O_WRONLY.
>  	 */
>  	new_file = dentry_open(path,
> -			       group->fanotify_data.f_flags | FMODE_NONOTIFY,
> +			       group->fanotify_data.f_flags | __FMODE_NONOTIFY,
>  			       current_cred());
>  	if (IS_ERR(new_file)) {
>  		/*
> @@ -1348,7 +1348,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
>  	    (!(fid_mode & FAN_REPORT_NAME) || !(fid_mode & FAN_REPORT_FID)))
>  		return -EINVAL;
>  
> -	f_flags = O_RDWR | FMODE_NONOTIFY;
> +	f_flags = O_RDWR | __FMODE_NONOTIFY;
>  	if (flags & FAN_CLOEXEC)
>  		f_flags |= O_CLOEXEC;
>  	if (flags & FAN_NONBLOCK)
> diff --git a/fs/open.c b/fs/open.c
> index 1315253e0247..386c52e4c3b1 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -1021,7 +1021,7 @@ inline struct open_how build_open_how(int flags, umode_t mode)
>  inline int build_open_flags(const struct open_how *how, struct open_flags *op)
>  {
>  	u64 flags = how->flags;
> -	u64 strip = FMODE_NONOTIFY | O_CLOEXEC;
> +	u64 strip = __FMODE_NONOTIFY | O_CLOEXEC;
>  	int lookup_flags = 0;
>  	int acc_mode = ACC_MODE(flags);
>  
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index c1031843cc6a..b8ed41eb5784 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -2233,11 +2233,21 @@ static const struct inode_operations proc_map_files_link_inode_operations = {
>  	.setattr	= proc_setattr,
>  };
>  
> +static fmode_t fmode_instantiate_decode(const void *ptr)
> +{
> +	return (__force fmode_t)(unsigned long)ptr;
> +}
> +
> +static void *fmode_instantiate_encode(fmode_t fmode)
> +{
> +	return (void *)(__force unsigned long)fmode;
> +}
> +
>  static struct dentry *
>  proc_map_files_instantiate(struct dentry *dentry,
>  			   struct task_struct *task, const void *ptr)
>  {
> -	fmode_t mode = (fmode_t)(unsigned long)ptr;
> +	fmode_t mode = fmode_instantiate_decode(ptr);
>  	struct proc_inode *ei;
>  	struct inode *inode;
>  
> @@ -2292,10 +2302,11 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
>  	if (!vma)
>  		goto out_no_vma;
>  
> -	if (vma->vm_file)
> -		result = proc_map_files_instantiate(dentry, task,
> -				(void *)(unsigned long)vma->vm_file->f_mode);
> +	if (vma->vm_file) {
> +		void *ptr = fmode_instantiate_encode(vma->vm_file->f_mode);
>  
> +		result = proc_map_files_instantiate(dentry, task, ptr);
> +	}
>  out_no_vma:
>  	mmap_read_unlock(mm);
>  out_put_mm:
> @@ -2391,7 +2402,7 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
>  				      buf, len,
>  				      proc_map_files_instantiate,
>  				      task,
> -				      (void *)(unsigned long)p->mode))
> +				      (void *)(__force unsigned long)p->mode))
>  			break;
>  		ctx->pos++;
>  	}
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR