Re: [PATCH] audit: Fix check of return value of strnlen_user()

On Wed 03-06-15 14:56:18, Paul Moore wrote: > On Tuesday, June 02, 2015 05:08:29 PM Jan Kara wrote: > > strnlen_user() returns 0 when it hits fault, not -1. Fix the test in > > audit_log_single_execve_arg(). Luckily this shouldn't ever happen unless > > there's a kernel bug so it's mostly a cosmetic fix. > > > > CC: Paul Moore <pmoore(a)redhat.com&gt; > > Signed-off-by: Jan Kara <jack(a)suse.cz&gt; > > --- > > kernel/auditsc.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > > index 9fb9d1cb83ce..bb947ceeee4d 100644 > > --- a/kernel/auditsc.c > > +++ b/kernel/auditsc.c > > @@ -1023,7 +1023,7 @@ static int audit_log_single_execve_arg(struct > > audit_context *context, * for strings that are too long, we should not have > > created > > * any. > > */ > > - if (unlikely((len == -1) || len > MAX_ARG_STRLEN - 1)) { > > + if (unlikely((len == 0) || len > MAX_ARG_STRLEN - 1)) { > > While we're at it, should we make it just "len > MAX_ARG_STRLEN" as well? > Reading the comments in include/uapi/linux/binfmts.h as well as > valid_arg_len() that seems to be the correct logic. Umm, but audit_log_single_execve_arg() does decrement 1 from strnlen_user() result before doing the comparison. So the current test seems to match the one in valid_arg_len() exactly...