Previously, I fixed a tailcall infinite loop issue caused by trampoline[0].
At this time, I fix a tailcall infinite loop issue caused by tailcall and
freplace combination by preventing updating extended prog to prog_array map
and preventing extending tail callee prog with freplace:
1. If a prog or its subprog has been extended by freplace prog, the prog
can not be updated to prog_array map.
2. If a prog has been updated to prog_array map, it or its subprog can not
be extended by freplace prog.
v3 -> v4:
* Address comments from Eduard:
* Rename 'tail_callee_cnt' to 'prog_array_member_cnt'.
* Add comment to 'prog_array_member_cnt'.
* Use a mutex to protect 'is_extended' and 'prog_array_member_cnt'.
v2 -> v3:
* Address comments from Alexei:
* Stop hacking JIT.
* Prevent the specific use case at attach/update time.
v1 -> v2:
* Address comment from Eduard:
* Explain why nop5 and xor/nop3 are swapped at prologue.
* Address comment from Alexei:
* Disallow attaching tail_call_reachable freplace prog to
not-tail_call_reachable target in verifier.
* Update "bpf, arm64: Fix tailcall infinite loop caused by freplace" with
latest arm64 JIT code.
Links:
[0] https://lore.kernel.org/bpf/20230912150442.2009-1-hffilwlqm@xxxxxxxxx/
Leon Hwang (4):
bpf: Prevent updating extended prog to prog_array map
bpf: Prevent extending tail callee prog with freplace prog
selftests/bpf: Add a test case to confirm a tailcall infinite loop
issue has been prevented
selftests/bpf: Add cases to test tailcall in freplace
include/linux/bpf.h | 3 +
kernel/bpf/arraymap.c | 30 ++-
kernel/bpf/core.c | 1 +
kernel/bpf/syscall.c | 53 ++++-
.../selftests/bpf/prog_tests/tailcalls.c | 196 +++++++++++++++++-
.../tailcall_bpf2bpf_hierarchy_freplace.c | 30 +++
.../testing/selftests/bpf/progs/tc_bpf2bpf.c | 37 +++-
7 files changed, 335 insertions(+), 15 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy_freplace.c
--
2.44.0
