diff mbox series

[bpf-next,3/3] selftests/bpf: Add various tests to check helper access into ptr_to_btf_id.

Message ID 20230313235845.61029-4-alexei.starovoitov@gmail.com (mailing list archive)
State Accepted
Commit f25fd6088216bd257902e5c212177cddcb291218
Delegated to: BPF
Headers show
Series bpf: Allow helpers access ptr_to_btf_id. | expand

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bpf/vmtest-bpf-next-PR success PR summary
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 20 this patch: 20
netdev/cc_maintainers warning 11 maintainers not CCed: linux-kselftest@vger.kernel.org mykolal@fb.com song@kernel.org shuah@kernel.org sdf@google.com haoluo@google.com yhs@fb.com john.fastabend@gmail.com kpsingh@kernel.org jolsa@kernel.org martin.lau@linux.dev
netdev/build_clang success Errors and warnings before: 18 this patch: 18
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netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
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netdev/checkpatch warning WARNING: line length of 85 exceeds 80 columns
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Commit Message

Alexei Starovoitov March 13, 2023, 11:58 p.m. UTC 
From: Alexei Starovoitov <ast@kernel.org>

Add various tests to check helper access into ptr_to_btf_id.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 .../selftests/bpf/progs/task_kfunc_failure.c  | 36 +++++++++++++++++++
 .../selftests/bpf/progs/task_kfunc_success.c  |  4 +++
 2 files changed, 40 insertions(+)

Comments

David Vernet March 14, 2023, 12:15 a.m. UTC | #1 
On Mon, Mar 13, 2023 at 04:58:45PM -0700, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.org>
> 
> Add various tests to check helper access into ptr_to_btf_id.
> 
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Thanks a lot for the quick turnaround on this.

LGTM, just left one small nit below.

Acked-by: David Vernet <void@manifault.com>

> ---
>  .../selftests/bpf/progs/task_kfunc_failure.c  | 36 +++++++++++++++++++
>  .../selftests/bpf/progs/task_kfunc_success.c  |  4 +++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> index 002c7f69e47f..27994d6b2914 100644
> --- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> +++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> @@ -301,3 +301,39 @@ int BPF_PROG(task_kfunc_from_lsm_task_free, struct task_struct *task)
>  	bpf_task_release(acquired);
>  	return 0;
>  }
> +
> +SEC("tp_btf/task_newtask")
> +__failure __msg("access beyond the end of member comm")
> +int BPF_PROG(task_access_comm1, struct task_struct *task, u64 clone_flags)
> +{
> +	bpf_strncmp(task->comm, 17, "foo");

Instead of 17, can you do either TASK_COMM_LEN + 1, or
sizeof(task->comm) + 1, to make the test a bit less brittle? Applies to
the other testcases as well.

> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +__failure __msg("access beyond the end of member comm")
> +int BPF_PROG(task_access_comm2, struct task_struct *task, u64 clone_flags)
> +{
> +	bpf_strncmp(task->comm + 1, 16, "foo");
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +__failure __msg("write into memory")
> +int BPF_PROG(task_access_comm3, struct task_struct *task, u64 clone_flags)
> +{
> +	bpf_probe_read_kernel(task->comm, 16, task->comm);
> +	return 0;
> +}
> +
> +SEC("fentry/__set_task_comm")
> +__failure __msg("R1 type=ptr_ expected")
> +int BPF_PROG(task_access_comm4, struct task_struct *task, const char *buf, bool exec)
> +{
> +	/*
> +	 * task->comm is a legacy ptr_to_btf_id. The verifier cannot guarantee
> +	 * its safety. Hence it cannot be accessed with normal load insns.
> +	 */
> +	bpf_strncmp(task->comm, 16, "foo");
> +	return 0;
> +}
> diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_success.c b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
> index aebc4bb14e7d..4f61596b0242 100644
> --- a/tools/testing/selftests/bpf/progs/task_kfunc_success.c
> +++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
> @@ -207,6 +207,10 @@ int BPF_PROG(test_task_from_pid_invalid, struct task_struct *task, u64 clone_fla
>  	if (!is_test_kfunc_task())
>  		return 0;
>  
> +	bpf_strncmp(task->comm, 12, "foo");
> +	bpf_strncmp(task->comm, 16, "foo");
> +	bpf_strncmp(&task->comm[8], 4, "foo");
> +
>  	if (is_pid_lookup_valid(-1)) {
>  		err = 1;
>  		return 0;
> -- 
> 2.34.1
>
Alexei Starovoitov March 14, 2023, 12:19 a.m. UTC | #2 
On Mon, Mar 13, 2023 at 5:15 PM David Vernet <void@manifault.com> wrote:
>
> On Mon, Mar 13, 2023 at 04:58:45PM -0700, Alexei Starovoitov wrote:
> > From: Alexei Starovoitov <ast@kernel.org>
> >
> > Add various tests to check helper access into ptr_to_btf_id.
> >
> > Signed-off-by: Alexei Starovoitov <ast@kernel.org>
>
> Thanks a lot for the quick turnaround on this.
>
> LGTM, just left one small nit below.
>
> Acked-by: David Vernet <void@manifault.com>
>
> > ---
> >  .../selftests/bpf/progs/task_kfunc_failure.c  | 36 +++++++++++++++++++
> >  .../selftests/bpf/progs/task_kfunc_success.c  |  4 +++
> >  2 files changed, 40 insertions(+)
> >
> > diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> > index 002c7f69e47f..27994d6b2914 100644
> > --- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> > +++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> > @@ -301,3 +301,39 @@ int BPF_PROG(task_kfunc_from_lsm_task_free, struct task_struct *task)
> >       bpf_task_release(acquired);
> >       return 0;
> >  }
> > +
> > +SEC("tp_btf/task_newtask")
> > +__failure __msg("access beyond the end of member comm")
> > +int BPF_PROG(task_access_comm1, struct task_struct *task, u64 clone_flags)
> > +{
> > +     bpf_strncmp(task->comm, 17, "foo");
>
> Instead of 17, can you do either TASK_COMM_LEN + 1, or
> sizeof(task->comm) + 1, to make the test a bit less brittle? Applies to
> the other testcases as well.

I'd rather not, since it's not brittle.
There were several attempts in the past to increase TASK_COMM_LEN
and all failed. It will stay 16 for the foreseeable future.
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
index 002c7f69e47f..27994d6b2914 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
@@ -301,3 +301,39 @@  int BPF_PROG(task_kfunc_from_lsm_task_free, struct task_struct *task)
 	bpf_task_release(acquired);
 	return 0;
 }
+
+SEC("tp_btf/task_newtask")
+__failure __msg("access beyond the end of member comm")
+int BPF_PROG(task_access_comm1, struct task_struct *task, u64 clone_flags)
+{
+	bpf_strncmp(task->comm, 17, "foo");
+	return 0;
+}
+
+SEC("tp_btf/task_newtask")
+__failure __msg("access beyond the end of member comm")
+int BPF_PROG(task_access_comm2, struct task_struct *task, u64 clone_flags)
+{
+	bpf_strncmp(task->comm + 1, 16, "foo");
+	return 0;
+}
+
+SEC("tp_btf/task_newtask")
+__failure __msg("write into memory")
+int BPF_PROG(task_access_comm3, struct task_struct *task, u64 clone_flags)
+{
+	bpf_probe_read_kernel(task->comm, 16, task->comm);
+	return 0;
+}
+
+SEC("fentry/__set_task_comm")
+__failure __msg("R1 type=ptr_ expected")
+int BPF_PROG(task_access_comm4, struct task_struct *task, const char *buf, bool exec)
+{
+	/*
+	 * task->comm is a legacy ptr_to_btf_id. The verifier cannot guarantee
+	 * its safety. Hence it cannot be accessed with normal load insns.
+	 */
+	bpf_strncmp(task->comm, 16, "foo");
+	return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_success.c b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
index aebc4bb14e7d..4f61596b0242 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_success.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
@@ -207,6 +207,10 @@  int BPF_PROG(test_task_from_pid_invalid, struct task_struct *task, u64 clone_fla
 	if (!is_test_kfunc_task())
 		return 0;
 
+	bpf_strncmp(task->comm, 12, "foo");
+	bpf_strncmp(task->comm, 16, "foo");
+	bpf_strncmp(&task->comm[8], 4, "foo");
+
 	if (is_pid_lookup_valid(-1)) {
 		err = 1;
 		return 0;