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.
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.
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
>
