Re: [PATCH bpf-next v3 3/4] bpf_trace: handle compat in copy_user_syms

On Tue, May 17, 2022 at 12:36 AM Eugene Syromiatnikov esyr@redhat.com wrote:

For compat processes, userspace size for syms pointers is different. Provide compat handling for copying array elements from the user space.

Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link") Signed-off-by: Eugene Syromiatnikov esyr@redhat.com

---

kernel/trace/bpf_trace.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index a93a54f..9d3028a 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2253,6 +2253,24 @@ struct user_syms { char *buf; };

+static inline int get_arr_ptr(unsigned long *p,

•                         unsigned long __user *uaddr, u32 idx)
  

no need for inline, let compiler decide on inlining

+{

•   if (unlikely(in_compat_syscall())) {
  

not sure unlikely() is justified for code...

•           compat_uptr_t __user *compat_uaddr = (compat_uptr_t __user *)uaddr;
  

•           compat_uptr_t val;
  

•           int err;
  

•           err = __get_user(val, compat_uaddr + idx);
  

•           if (!err)
  

•                   *p = val;
  

•           return err;
  

•   } else {
  

•           return __get_user(*p, uaddr + idx);
  

•   }
  

+}

static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt) { unsigned long __user usymbol; @@ -2270,7 +2288,7 @@ static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 goto error;

    for (p = buf, i = 0; i < cnt; i++) {

•           if (__get_user(usymbol, usyms + i)) {
  

•           if (get_arr_ptr(&usymbol, usyms, i)) {
                    err = -EFAULT;
                    goto error;
            }
  

-- 2.1.4