linux-kernel - Re: [PATCH linux-next] selinux: use sysfs

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Message-ID: <CAJ2a_Df3QmeteqHVJ3hp7X-t3UsBNwgzu-utfTq1rDMJdwEz0A@mail.gmail.com>
Date: Sun, 16 Mar 2025 14:38:09 +0100
From: Christian Göttsche <cgzones@...glemail.com>
To: xie.ludan@....com.cn
Cc: stephen.smalley.work@...il.com, paul@...l-moore.com, omosnace@...hat.com, 
	selinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH linux-next] selinux: use sysfs_emit() instead of scnprintf()

On Sat, 15 Mar 2025 at 07:11, <xie.ludan@....com.cn> wrote:
>
> From: XieLudan <xie.ludan@....com.cn>
>
>
> Follow the advice in Documentation/filesystems/sysfs.rst:
>
> show() should only use sysfs_emit() or sysfs_emit_at() when formatting
>
> the value to be returned to user space.
>
>
> Signed-off-by: XieLudan <xie.ludan@....com.cn>
>
> ---
>
>  security/selinux/selinuxfs.c | 20 ++++++++++----------
>
>  1 file changed, 10 insertions(+), 10 deletions(-)
>
>
> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
>
> index 47480eb2189b..17c56fc87d98 100644
>
> --- a/security/selinux/selinuxfs.c
>
> +++ b/security/selinux/selinuxfs.c
>
> @@ -126,7 +126,7 @@ static ssize_t sel_read_enforce(struct file *filp, char __user *buf,
>
>   char tmpbuf[TMPBUFLEN];
>
>   ssize_t length;
>
>
>
> - length = scnprintf(tmpbuf, TMPBUFLEN, "%d",
>
> + length = sysfs_emit(tmpbuf, "%d",

That would be dangerous since the target buffer is of size TMPBUFLEN
(12) and not PAGE_SIZE (4096).

>      enforcing_enabled());
>
>   return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
>
>  }
>
> @@ -206,7 +206,7 @@ static ssize_t sel_read_handle_unknown(struct file *filp, char __user *buf,
>
>   security_get_reject_unknown() :
>
>   !security_get_allow_unknown();
>
>
>
> - length = scnprintf(tmpbuf, TMPBUFLEN, "%d", handle_unknown);
>
> + length = sysfs_emit(tmpbuf, "%d", handle_unknown);
>
>   return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
>
>  }
>
>
>
> @@ -314,7 +314,7 @@ static ssize_t sel_read_policyvers(struct file *filp, char __user *buf,
>
>   char tmpbuf[TMPBUFLEN];
>
>   ssize_t length;
>
>
>
> - length = scnprintf(tmpbuf, TMPBUFLEN, "%u", POLICYDB_VERSION_MAX);
>
> + length = sysfs_emit(tmpbuf, "%u", POLICYDB_VERSION_MAX);
>
>   return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
>
>  }
>
>
>
> @@ -345,7 +345,7 @@ static ssize_t sel_read_mls(struct file *filp, char __user *buf,
>
>   char tmpbuf[TMPBUFLEN];
>
>   ssize_t length;
>
>
>
> - length = scnprintf(tmpbuf, TMPBUFLEN, "%d",
>
> + length = sysfs_emit(tmpbuf, "%d",
>
>      security_mls_enabled());
>
>   return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
>
>  }
>
> @@ -670,7 +670,7 @@ static ssize_t sel_read_checkreqprot(struct file *filp, char __user *buf,
>
>   char tmpbuf[TMPBUFLEN];
>
>   ssize_t length;
>
>
>
> - length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
>
> + length = sysfs_emit(tmpbuf, "%u",
>
>      checkreqprot_get());
>
>   return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
>
>  }
>
> @@ -1226,7 +1226,7 @@ static ssize_t sel_read_bool(struct file *filep, char __user *buf,
>
>   ret = cur_enforcing;
>
>   goto out_unlock;
>
>   }
>
> - length = scnprintf(page, PAGE_SIZE, "%d %d", cur_enforcing,
>
> + length = sysfs_emit(page, "%d %d", cur_enforcing,
>
>     fsi->bool_pending_values[index]);
>
>   mutex_unlock(&selinux_state.policy_mutex);
>
>   ret = simple_read_from_buffer(buf, count, ppos, page, length);
>
> @@ -1416,7 +1416,7 @@ static ssize_t sel_read_avc_cache_threshold(struct file *filp, char __user *buf,
>
>   char tmpbuf[TMPBUFLEN];
>
>   ssize_t length;
>
>
>
> - length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
>
> + length = sysfs_emit(tmpbuf, "%u",
>
>      avc_get_cache_threshold());
>
>   return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
>
>  }
>
> @@ -1726,7 +1726,7 @@ static ssize_t sel_read_class(struct file *file, char __user *buf,
>
>  {
>
>   unsigned long ino = file_inode(file)->i_ino;
>
>   char res[TMPBUFLEN];
>
> - ssize_t len = scnprintf(res, sizeof(res), "%d", sel_ino_to_class(ino));
>
> + ssize_t len = sysfs_emit(res, "%d", sel_ino_to_class(ino));
>
>   return simple_read_from_buffer(buf, count, ppos, res, len);
>
>  }
>
>
>
> @@ -1740,7 +1740,7 @@ static ssize_t sel_read_perm(struct file *file, char __user *buf,
>
>  {
>
>   unsigned long ino = file_inode(file)->i_ino;
>
>   char res[TMPBUFLEN];
>
> - ssize_t len = scnprintf(res, sizeof(res), "%d", sel_ino_to_perm(ino));
>
> + ssize_t len = sysfs_emit(res, "%d", sel_ino_to_perm(ino));
>
>   return simple_read_from_buffer(buf, count, ppos, res, len);
>
>  }
>
>
>
> @@ -1758,7 +1758,7 @@ static ssize_t sel_read_policycap(struct file *file, char __user *buf,
>
>   unsigned long i_ino = file_inode(file)->i_ino;
>
>
>
>   value = security_policycap_supported(i_ino & SEL_INO_MASK);
>
> - length = scnprintf(tmpbuf, TMPBUFLEN, "%d", value);
>
> + length = sysfs_emit(tmpbuf, "%d", value);
>
>
>
>   return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
>
>  }
>
> --
>
> 2.25.1
>
>
>
>