2022-06-17 05:17:09

by Ian Kent

Subject: [PATCH 1/2] vfs: parse: deal with zero length string value

Parsing an fs string that has zero length should result in the parameter
being set to NULL so that downstream processing handles it correctly.
For example, the proc mount table processing should print "(none)" in
this case to preserve mount record field count, but if the value points
to the NULL string this doesn't happen.

Signed-off-by: Ian Kent <[email protected]>
---
fs/fs_context.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/fs_context.c b/fs/fs_context.c
index 24ce12f0db32..4c735d0ce3cb 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -175,9 +175,13 @@ int vfs_parse_fs_string(struct fs_context *fc, const char *key,
};

if (value) {
- param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
- if (!param.string)
- return -ENOMEM;
+ if (!v_size)
+ param.string = NULL;
+ else {
+ param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
+ if (!param.string)
+ return -ENOMEM;
+ }
param.type = fs_value_is_string;
}

2022-06-28 13:16:33

by Christian Brauner

Subject: Re: [PATCH 1/2] vfs: parse: deal with zero length string value

On Fri, Jun 17, 2022 at 01:09:03PM +0800, Ian Kent wrote:
> Parsing an fs string that has zero length should result in the parameter
> being set to NULL so that downstream processing handles it correctly.
> For example, the proc mount table processing should print "(none)" in
> this case to preserve mount record field count, but if the value points
> to the NULL string this doesn't happen.
>
> Signed-off-by: Ian Kent <[email protected]>
> ---

Makes sense. Though I feel this is might be one of those instances where
we detect that some code isn't prepared for param.string to be NULL at
some point...
Reviewed-by: Christian Brauner (Microsoft) <[email protected]>