On Thu, Feb 17, 2022 at 6:22 AM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> Commit e3489f8974e1 ("selinux: kill selinux_sb_get_mnt_opts()")
> introduced a NULL check on the context after a successful call to
> security_sid_to_context(). This is on the one hand redundant after
> checking for success and on the other hand insufficient on an actual
> NULL pointer, since the context is passed to seq_escape() leading to a
> call of strlen() on it.
>
> Reported by Clang analyzer:
>
> In file included from security/selinux/hooks.c:28:
> In file included from ./include/linux/tracehook.h:50:
> In file included from ./include/linux/memcontrol.h:13:
> In file included from ./include/linux/cgroup.h:18:
> ./include/linux/seq_file.h:136:25: warning: Null pointer passed as 1st argument to string length function [unix.cstring.NullArg]
> seq_escape_mem(m, src, strlen(src), flags, esc);
> ^~~~~~~~~~~
I'm guessing there was more to this trace for this instance of this warning?
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
> ---
> security/selinux/hooks.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 1e69f88eb326..ac802b99d36c 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1020,7 +1020,7 @@ static int show_sid(struct seq_file *m, u32 sid)
> rc = security_sid_to_context(&selinux_state, sid,
> &context, &len);
> if (!rc) {
^ perhaps changing this condition to:
if (!rc && context) {
It might be nice to retain the null ptr check should the semantics of
security_sid_to_context ever change.
> - bool has_comma = context && strchr(context, ',');
> + bool has_comma = strchr(context, ',');
>
> seq_putc(m, '=');
> if (has_comma)
> --
> 2.35.1
>
--
Thanks,
~Nick Desaulniers
