This patch set fixes BPF verifier logic around validating and enforcing return
values for BPF programs that have specific range of expected return values.
Both sync and async callbacks have similar logic and are fixes as well.
A few tests are added that would fail without the fixes in this patch set.
Also, while at it, we update retval checking logic to use smin/smax range
instead of tnum, avoiding future potential issues if expected range cannot be
represented precisely by tnum (e.g., [0, 2] is not representable by tnum and
is treated as [0, 3]).
There is a little bit of refactoring to unify async callback and program exit
logic to avoid duplication of checks as much as possible.
v3->v4:
- add back bpf_func_state rearrangement patch;
- simplified patch #4 as suggested (Shung-Hsi);
v2->v3:
- more carefullly switch from umin/umax to smin/smax;
v1->v2:
- drop tnum from retval checks (Eduard);
- use smin/smax instead of umin/umax (Alexei).
Andrii Nakryiko (11):
bpf: rearrange bpf_func_state fields to save a bit of memory
bpf: provide correct register name for exception callback retval check
bpf: enforce precision of R0 on callback return
bpf: enforce exact retval range on subprog/callback exit
selftests/bpf: add selftest validating callback result is enforced
bpf: enforce precise retval range on program exit
bpf: unify async callback and program retval checks
bpf: enforce precision of R0 on program/async callback return
selftests/bpf: validate async callback return value check correctness
selftests/bpf: adjust global_func15 test to validate prog exit
precision
bpf: simplify tnum output if a fully known constant
include/linux/bpf_verifier.h | 9 +-
kernel/bpf/log.c | 13 ++
kernel/bpf/tnum.c | 6 -
kernel/bpf/verifier.c | 120 ++++++++++--------
.../selftests/bpf/progs/exceptions_assert.c | 2 +-
.../selftests/bpf/progs/exceptions_fail.c | 2 +-
.../selftests/bpf/progs/test_global_func15.c | 34 ++++-
.../selftests/bpf/progs/timer_failure.c | 36 ++++--
.../selftests/bpf/progs/user_ringbuf_fail.c | 2 +-
.../bpf/progs/verifier_cgroup_inv_retcode.c | 8 +-
.../bpf/progs/verifier_direct_packet_access.c | 2 +-
.../selftests/bpf/progs/verifier_int_ptr.c | 2 +-
.../bpf/progs/verifier_netfilter_retcode.c | 2 +-
.../selftests/bpf/progs/verifier_stack_ptr.c | 4 +-
.../bpf/progs/verifier_subprog_precision.c | 50 ++++++++
15 files changed, 212 insertions(+), 80 deletions(-)
--
2.34.1
