linux-kernel - Re: [PATCH v2] btrfs: replace deprecated strcpy with strscpy

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Message-ID: <b8945d37-3eb9-4ad6-b3eb-2725dbb008ad@harmstone.com>
Date: Thu, 19 Jun 2025 18:06:12 +0100
From: Mark Harmstone <mark@...mstone.com>
To: Brahmajit Das <listout@...tout.xyz>, linux-hardening@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org
Cc: clm@...com, josef@...icpanda.com, dsterba@...e.com, kees@...nel.org,
 ailiop@...e.com
Subject: Re: [PATCH v2] btrfs: replace deprecated strcpy with strscpy

On 19/06/2025 4.39 pm, Brahmajit Das wrote:
> strcpy is deprecated due to lack of bounds checking. This patch replaces
> strcpy with strscpy, the recommended alternative for null terminated
> strings, to follow best practices.
> 
> There are instances where strscpy cannot be used such as where both the
> source and destination are character pointers. In that instance we can
> use sysfs_emit or a memcpy.
> 
> Update in v2: using sysfs_emit instead of scnprintf
> 
> No functional changes intended.
> 
> Link: https://github.com/KSPP/linux/issues/88
> 
> Suggested-by: Anthony Iliopoulos <ailiop@...e.com>
> Signed-off-by: Brahmajit Das <listout@...tout.xyz>
> ---
>   fs/btrfs/ioctl.c   | 2 +-
>   fs/btrfs/send.c    | 2 +-
>   fs/btrfs/volumes.c | 2 +-
>   fs/btrfs/xattr.c   | 4 ++--
>   4 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 913acef3f0a9..203f309f00b1 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4200,7 +4200,7 @@ static int btrfs_ioctl_set_fslabel(struct file *file, void __user *arg)
>   	}
>   
>   	spin_lock(&fs_info->super_lock);
> -	strcpy(super_block->label, label);
> +	strscpy(super_block->label, label);
>   	spin_unlock(&fs_info->super_lock);
>   	ret = btrfs_commit_transaction(trans);

Surely this doesn't compile... strscpy takes three parameters.

> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index 2891ec4056c6..66ee9e1b1e96 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -758,7 +758,7 @@ static int send_header(struct send_ctx *sctx)
>   {
>   	struct btrfs_stream_header hdr;
>   
> -	strcpy(hdr.magic, BTRFS_SEND_STREAM_MAGIC);
> +	strscpy(hdr.magic, BTRFS_SEND_STREAM_MAGIC);
>   	hdr.version = cpu_to_le32(sctx->proto);
>   	return write_buf(sctx->send_filp, &hdr, sizeof(hdr),
>   					&sctx->send_off);
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 89835071cfea..ec5304f19ac2 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -215,7 +215,7 @@ void btrfs_describe_block_groups(u64 bg_flags, char *buf, u32 size_buf)
>   	u32 size_bp = size_buf;
>   
>   	if (!flags) {
> -		strcpy(bp, "NONE");
> +		memcpy(bp, "NONE", 4);
>   		return;
>   	}

Same issue here as with the other patch.

>   
> diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
> index 3e0edbcf73e1..9f652932895c 100644
> --- a/fs/btrfs/xattr.c
> +++ b/fs/btrfs/xattr.c
> @@ -12,6 +12,7 @@
>   #include <linux/posix_acl_xattr.h>
>   #include <linux/iversion.h>
>   #include <linux/sched/mm.h>
> +#include <linux/string.h>
>   #include "ctree.h"
>   #include "fs.h"
>   #include "messages.h"
> @@ -516,8 +517,7 @@ static int btrfs_initxattrs(struct inode *inode,
>   			ret = -ENOMEM;
>   			break;
>   		}
> -		strcpy(name, XATTR_SECURITY_PREFIX);
> -		strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
> +		sysfs_emit(name, "%s%s", XATTR_SECURITY_PREFIX, xattr->name);
>   
>   		if (strcmp(name, XATTR_NAME_CAPS) == 0)
>   			clear_bit(BTRFS_INODE_NO_CAP_XATTR, &BTRFS_I(inode)->runtime_flags);