On Mon, Apr 12, 2021 at 11:02:19AM +0800, Tiezhu Yang wrote:
> On 04/11/2021 07:04 PM, Jinyang He wrote:
> > Commit 04324f44cb69 ("MIPS: Remove get_fs/set_fs") brought a problem for
> > strnlen_user(). Jump out when checking access_ok() with condition that
> > (s + strlen(s)) < __UA_LIMIT <= (s + n). The old __strnlen_user_asm()
> > just checked (ua_limit & s) without checking (ua_limit & (s + n)).
> > Therefore, find strlen form s to __UA_LIMIT - 1 in that condition.
> >
> > Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
> > ---
> > arch/mips/include/asm/uaccess.h | 11 +++++++++--
> > 1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
> > index 91bc7fb..85ba0c8 100644
> > --- a/arch/mips/include/asm/uaccess.h
> > +++ b/arch/mips/include/asm/uaccess.h
> > @@ -630,8 +630,15 @@ static inline long strnlen_user(const char __user *s, long n)
> > {
> > long res;
> > - if (!access_ok(s, n))
> > - return -0;
> > + if (unlikely(n <= 0))
> > + return 0;
> > +
> > + if (!access_ok(s, n)) {
> > + if (!access_ok(s, 0))
> > + return 0;
> > +
> > + n = __UA_LIMIT - (unsigned long)s - 1;
> > + }
> > might_fault();
> > __asm__ __volatile__(
>
> The following simple changes are OK to fix this issue?
>
> diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
> index 91bc7fb..eafc99b 100644
> --- a/arch/mips/include/asm/uaccess.h
> +++ b/arch/mips/include/asm/uaccess.h
> @@ -630,8 +630,8 @@ static inline long strnlen_user(const char __user *s, long n)
> {
> long res;
> - if (!access_ok(s, n))
> - return -0;
> + if (!access_ok(s, 1))
> + return 0;
> might_fault();
> __asm__ __volatile__(
that's the fix I'd like to apply. Could someone send it as a formal
patch ? Thanks.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
