On Mon, Jun 03, 2024 at 09:25:47AM -0700, Alexei Starovoitov wrote:
> On Mon, Jun 3, 2024 at 4:14 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> >
> > syzbot reported crash when rawtp program executed through the
> > test_run interface calls bpf_get_attach_cookie helper or any
> > other helper that touches task->bpf_ctx pointer.
> >
> > We need to setup bpf_ctx pointer in rawtp test_run as well,
> > so fixing this by moving __bpf_trace_run in header file and
> > using it in test_run callback.
> >
> > Also renaming __bpf_trace_run to bpf_prog_run_trace.
> >
> > Fixes: 7adfc6c9b315 ("bpf: Add bpf_get_attach_cookie() BPF helper to access bpf_cookie value")
> > Reported-by: syzbot+3ab78ff125b7979e45f9@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://syzkaller.appspot.com/bug?extid=3ab78ff125b7979e45f9
> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > ---
> > include/linux/bpf.h | 27 +++++++++++++++++++++++++++
> > kernel/trace/bpf_trace.c | 28 ++--------------------------
> > net/bpf/test_run.c | 4 +---
> > 3 files changed, 30 insertions(+), 29 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 5e694a308081..4eb803b1d308 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -2914,6 +2914,33 @@ static inline void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr)
> > }
> > #endif /* CONFIG_BPF_SYSCALL */
> >
> > +static __always_inline int
> > +bpf_prog_run_trace(struct bpf_prog *prog, u64 cookie, u64 *ctx,
> > + bpf_prog_run_fn run_prog)
> > +{
> > + struct bpf_run_ctx *old_run_ctx;
> > + struct bpf_trace_run_ctx run_ctx;
> > + int ret = -1;
> > +
> > + cant_sleep();
>
> I suspect you should see a splat with that.
hum, __bpf_prog_test_run_raw_tp is called with preempt_disable,
so I think it should be fine
>
> Overall I think it's better to add empty run_ctx to
> __bpf_prog_test_run_raw_tp()
> instead of moving such a big function to .h
>
> No need for prog->active increments. test_run is running
> from syscall. If the same prog is attached somewhere as well
> it may recurse once and it's fine imo.
heh, it was my first change, then I was thinking let's not duplicate the
code and re-use the existing function.. but it's true that there's no
use for the prog->active intest_run interface
jirka
>
> pw-bot: cr
>
> > + if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
> > + bpf_prog_inc_misses_counter(prog);
> > + goto out;
> > + }
> > +
> > + run_ctx.bpf_cookie = cookie;
> > + old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> > +
> > + rcu_read_lock();
> > + ret = run_prog(prog, ctx);
> > + rcu_read_unlock();
> > +
> > + bpf_reset_run_ctx(old_run_ctx);
> > +out:
> > + this_cpu_dec(*(prog->active));
> > + return ret;
> > +}
> > +
> > static __always_inline int
> > bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
> > {
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index d1daeab1bbc1..8a23ef42b76b 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -2383,31 +2383,6 @@ void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp)
> > preempt_enable();
> > }
> >
> > -static __always_inline
> > -void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args)
> > -{
> > - struct bpf_prog *prog = link->link.prog;
> > - struct bpf_run_ctx *old_run_ctx;
> > - struct bpf_trace_run_ctx run_ctx;
> > -
> > - cant_sleep();
> > - if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
> > - bpf_prog_inc_misses_counter(prog);
> > - goto out;
> > - }
> > -
> > - run_ctx.bpf_cookie = link->cookie;
> > - old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> > -
> > - rcu_read_lock();
> > - (void) bpf_prog_run(prog, args);
> > - rcu_read_unlock();
> > -
> > - bpf_reset_run_ctx(old_run_ctx);
> > -out:
> > - this_cpu_dec(*(prog->active));
> > -}
> > -
> > #define UNPACK(...) __VA_ARGS__
> > #define REPEAT_1(FN, DL, X, ...) FN(X)
> > #define REPEAT_2(FN, DL, X, ...) FN(X) UNPACK DL REPEAT_1(FN, DL, __VA_ARGS__)
> > @@ -2437,7 +2412,8 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args)
> > { \
> > u64 args[x]; \
> > REPEAT(x, COPY, __DL_SEM, __SEQ_0_11); \
> > - __bpf_trace_run(link, args); \
> > + (void) bpf_prog_run_trace(link->link.prog, link->cookie,\
> > + args, bpf_prog_run); \
> > } \
> > EXPORT_SYMBOL_GPL(bpf_trace_run##x)
> > BPF_TRACE_DEFN_x(1);
> > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> > index f6aad4ed2ab2..84d1c91b01ab 100644
> > --- a/net/bpf/test_run.c
> > +++ b/net/bpf/test_run.c
> > @@ -728,9 +728,7 @@ __bpf_prog_test_run_raw_tp(void *data)
> > {
> > struct bpf_raw_tp_test_run_info *info = data;
> >
> > - rcu_read_lock();
> > - info->retval = bpf_prog_run(info->prog, info->ctx);
> > - rcu_read_unlock();
> > + info->retval = bpf_prog_run_trace(info->prog, 0, info->ctx, bpf_prog_run);
> > }
> >
> > int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
> > --
> > 2.45.1
> >
