2020-07-20 08:24:20

by Xiongfeng Wang

Subject: [PATCH] dlmfs: add a newline when printing 'capabilities' by sysfs

When I cat module parameter 'capabilities' by sysfs, it displays as
follows. It's better to add a newline for easy reading.

root@syzkaller:~# cat /sys/module/ocfs2_dlmfs/parameters/capabilities
bast stackglueroot@syzkaller:~#

Signed-off-by: Xiongfeng Wang <[email protected]>
---
fs/ocfs2/dlmfs/dlmfs.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index ea868c6f9800..1f9c864ec09b 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -82,8 +82,13 @@ static int param_set_dlmfs_capabilities(const char *val,
static int param_get_dlmfs_capabilities(char *buffer,
const struct kernel_param *kp)
{
- return strlcpy(buffer, DLMFS_CAPABILITIES,
+ int cnt;
+
+ cnt = strlcpy(buffer, DLMFS_CAPABILITIES,
strlen(DLMFS_CAPABILITIES) + 1);
+ cnt += sprintf(buffer + cnt, "\n");
+
+ return cnt;
}
module_param_call(capabilities, param_set_dlmfs_capabilities,
param_get_dlmfs_capabilities, NULL, 0444);
--
2.20.1

2020-07-21 02:26:43

by Changwei Ge

Subject: Re: [Ocfs2-devel] [PATCH] dlmfs: add a newline when printing 'capabilities' by sysfs

Hi，

I am afraid that doing so might introduce a compatible risk into exited
systems which reply ocfs2/dlmfs.

We can't guarantee that no system management tools is using the
information reported from this file.

Basically, ocfs2-tools works of top of it. But after a quick glance at
the source, I didn't see side effect if this path applied. Better you
can do some test if this patch breaks ocfs2-tools.

Still my suggestion is that we don't try to touch this file as what I
explained above.

Thanks,
Changwei


On 7/20/20 4:24 PM, Xiongfeng Wang wrote:
> When I cat module parameter 'capabilities' by sysfs, it displays as
> follows. It's better to add a newline for easy reading.
>
> root@syzkaller:~# cat /sys/module/ocfs2_dlmfs/parameters/capabilities
> bast stackglueroot@syzkaller:~#
>
> Signed-off-by: Xiongfeng Wang <[email protected]>
> ---
> fs/ocfs2/dlmfs/dlmfs.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
> index ea868c6f9800..1f9c864ec09b 100644
> --- a/fs/ocfs2/dlmfs/dlmfs.c
> +++ b/fs/ocfs2/dlmfs/dlmfs.c
> @@ -82,8 +82,13 @@ static int param_set_dlmfs_capabilities(const char *val,
> static int param_get_dlmfs_capabilities(char *buffer,
> const struct kernel_param *kp)
> {
> - return strlcpy(buffer, DLMFS_CAPABILITIES,
> + int cnt;
> +
> + cnt = strlcpy(buffer, DLMFS_CAPABILITIES,
> strlen(DLMFS_CAPABILITIES) + 1);
> + cnt += sprintf(buffer + cnt, "\n");
> +
> + return cnt;
> }
> module_param_call(capabilities, param_set_dlmfs_capabilities,
> param_get_dlmfs_capabilities, NULL, 0444);
>