On 2019-10-09, Christian Brauner wrote: > In v5.4-rc2 we added a new helper (cf. [1]) check_zeroed_user() which > does what bpf_check_uarg_tail_zero() is doing generically. We're slowly > switching such codepaths over to use check_zeroed_user() instead of > using their own hand-rolled version. > > [1]: f5a1a536fa14 ("lib: introduce copy_struct_from_user() helper") > Signed-off-by: Christian Brauner Acked-by: Aleksa Sarai > --- > kernel/bpf/syscall.c | 22 +++++++--------------- > 1 file changed, 7 insertions(+), 15 deletions(-) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 82eabd4e38ad..78790778f101 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -63,30 +63,22 @@ int bpf_check_uarg_tail_zero(void __user *uaddr, > size_t expected_size, > size_t actual_size) > { > - unsigned char __user *addr; > - unsigned char __user *end; > - unsigned char val; > + size_t size = min(expected_size, actual_size); > + size_t rest = max(expected_size, actual_size) - size; > int err; > > if (unlikely(actual_size > PAGE_SIZE)) /* silly large */ > return -E2BIG; > > - if (unlikely(!access_ok(uaddr, actual_size))) > - return -EFAULT; > - > if (actual_size <= expected_size) > return 0; > > - addr = uaddr + expected_size; > - end = uaddr + actual_size; > + err = check_zeroed_user(uaddr + expected_size, rest); > + if (err < 0) > + return err; > > - for (; addr < end; addr++) { > - err = get_user(val, addr); > - if (err) > - return err; > - if (val) > - return -E2BIG; > - } > + if (err) > + return -E2BIG; > > return 0; > } -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH