Re: [PATCH v10 8/9] proc: use human-readable values for hidehid

On Thu, Apr 02, 2020 at 11:05:21AM -0500, Eric W. Biederman wrote:

Alexey Gladkov [off-list ref] writes:

quoted

The hidepid parameter values are becoming more and more and it becomes
difficult to remember what each new magic number means.

In principle I like this change.  In practice I think you have just
broken ABI compatiblity with the new mount ABI.

In particular the following line seems broken.

quoted

diff --git a/fs/proc/root.c b/fs/proc/root.c
index dbcd96f07c7a..ba782d6e6197 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c

@@ -45,7 +45,7 @@ enum proc_param {
 
 static const struct fs_parameter_spec proc_fs_parameters[] = {
 	fsparam_u32("gid",	Opt_gid),
-	fsparam_u32("hidepid",	Opt_hidepid),
+	fsparam_string("hidepid",	Opt_hidepid),
 	fsparam_string("subset",	Opt_subset),
 	{}
 };

As I read fs_parser.c fs_param_is_u32 handles string inputs and turns them
into numbers, and it handles binary numbers.  However fs_param_is_string
appears to only handle strings.  It appears to have not capacity to turn
raw binary numbers into strings.

I use result only with hidepid_u32_spec and nobody modifies param->string.
I do not use internal functions here.

I don’t follow how a raw number can get here ?

So I think we probably need to fix fs_param_is_string to raw binary
numbers before we can safely make this change to fs/proc/root.c

David am I reading the fs_parser.c code correctly?  If I am are you ok
with a change like the above?

Eric

-- 
Rgrds, legion