Re: [PATCH v2 3/4] fs: unicode: Use strscpy() instead of strncpy()

[Shreeya Patel]

On 19/03/21 2:33 am, Eric Biggers wrote:
> On Thu, Mar 18, 2021 at 07:03:04PM +0530, Shreeya Patel wrote:
> > Following warning was reported by Kernel Test Robot.
> >
> > In function 'utf8_parse_version',
> > inlined from 'utf8_load' at fs/unicode/utf8mod.c:195:7:
> > > > fs/unicode/utf8mod.c:175:2: warning: 'strncpy' specified bound 12 equals
> > destination size [-Wstringop-truncation]
> > 175 |  strncpy(version_string, version, sizeof(version_string));
> >      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > The -Wstringop-truncation warning highlights the unintended
> > uses of the strncpy function that truncate the terminating NULL
> > character from the source string.
> > Unlike strncpy(), strscpy() always null-terminates the destination string,
> > hence use strscpy() instead of strncpy().
> >
> > Signed-off-by: Shreeya Patel <shreeya.patel@xxxxxxxxxxxxx>
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > ---
> > Changes in v2
> >    - Resolve warning of -Wstringop-truncation reported by
> >      kernel test robot.
> >
> >   fs/unicode/unicode-core.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/unicode/unicode-core.c b/fs/unicode/unicode-core.c
> > index d5f09e022ac5..287a8a48836c 100644
> > --- a/fs/unicode/unicode-core.c
> > +++ b/fs/unicode/unicode-core.c
> > @@ -179,7 +179,7 @@ static int unicode_parse_version(const char *version, unsigned int *maj,
> >   		{0, NULL}
> >   	};
> >   
> > -	strncpy(version_string, version, sizeof(version_string));
> > +	strscpy(version_string, version, sizeof(version_string));
> >   
> Shouldn't unicode_parse_version() return an error if the string gets truncated
> here?  I.e. check if strscpy() returns < 0.
>
> Also, this is a "fix" (though one that doesn't currently matter, since 'version'
> is currently always shorter than sizeof(version_string)), so it should go first
> in the series and have a Fixes tag.


Thanks Eric, will send v3 for it.

> - Eric