| #
5a8cd539 |
| 20-Aug-2026 |
Linus Torvalds <torvalds@linux-foundation.org> |
Merge tag 'bpf-next-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
Pull bpf updates from Daniel Borkmann:
"Major changes:
- Redesign the verifier error reporting: failures n
Merge tag 'bpf-next-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
Pull bpf updates from Daniel Borkmann:
"Major changes:
- Redesign the verifier error reporting: failures now carry source
and instruction annotations along with the causal event history
that led to them, making program rejections far easier to debug and
repair (Kumar Kartikeya Dwivedi)
- Add arena argument support to kfuncs and struct_ops through the new
__arena and __arena__nullable suffixes (Tejun Heo, Puranjay Mohan,
Kumar Kartikeya Dwivedi, Ihor Solodrai)
- Signed BPF program loader rework to accommodate both BPF and
security community needs where the kernel runs the signature
verification at BPF_PROG_LOAD time before the LSM admission hook
(Daniel Borkmann)
- Add a set of ksock kfuncs which let BPF LSM and syscall programs
create, connect and send on UDP sockets in order to emit telemetry
data (Mahe Tardy)
- Unify helper and kfunc call argument verification and classify
kfunc arguments purely from BTF into a generated bpf_func_proto
which is computed once at add-call time (Amery Hung)
Other features and fixes:
- Enable EXECMEM_ROX_CACHE for BPF allocations on x86 (Mike Rapoport)
- Add bidirectional VLAN support to bpf_fib_lookup() through the new
BPF_FIB_LOOKUP_VLAN and BPF_FIB_LOOKUP_VLAN_INPUT flags (Avinash
Duduskar)
- Infer zext_dst from static register liveness analysis to fix 32-bit
zero-extension semantics, and remove the artificial limitations on
pointer types eligible for spilling (Eduard Zingerman)
- Inline the numeric open-coded iterator kfuncs so that bpf_for()
loops no longer pay a kfunc call on every iteration (Puranjay
Mohan)
- Add an arena-based bitmap data structure to libarena along with
serial and parallel selftests (Emil Tsalapatis)
- Teach resolve_btfids to discover kfuncs from the kernel's BTF ID
sets and to emit kfunc BTF decl tags, reducing the kernel build's
dependency on pahole features (Ihor Solodrai)
- Add BPF_F_ADJ_ROOM_DECAP_* flags to bpf_skb_adjust_room() so that
tunnel decapsulation can update the GSO and encapsulation state of
the skb (Nick Hudson)
- Fix the ring buffer pending_pos walk and the available-data
accounting on 32-bit position wrap (Israel Téllez García)
- Add memory usage accounting for arena maps and fix an mmap_lock
deadlock on arena lock failure (Jiayuan Chen)
- Add tracing_multi link info support to the kernel UAPI and bpftool,
and refactor the stack map code to run with preemption disabled
(Jiri Olsa)
- Support BPF_F_EGRESS in bpf_redirect_peer() to emit the skb in the
egress direction of the target's peer device (Jordan Rife)
- Add a KF_SPINLOCK_SAFE kfunc flag so that providers, in particular
modules, can declare kfuncs safe to call under bpf_spin_lock
instead of relying on the verifier's hard-coded allowlist (Kaitao
Cheng)
- Introduce global percpu data for BPF programs with libbpf probing
and bpftool skeleton support, and stop exposing uninitialized
kernel heap memory when copying per-CPU map values (Leon Hwang)
- Add s390 JIT support for load-acquire and store-release
instructions (Maxim Khmelevskii)
- Fix a CFI mismatch in the task work callback and an arm64 KASAN
false positive after bpf_throw() (Mykyta Yatsenko)
- Reject writes through untrusted BTF pointers and bound the
rdonly/rdwr_buf_size kfunc arguments (Nicholas Dudar)
- Invalidate RCU pointers only after the final spin unlock and
account for preempt and IRQ disabled regions as overlapping RCU
protection (Ning Ding)
- Support mixing bpf2bpf calls and tail calls on RV64, add signed
operations and 32-bit atomics to the RV32 JIT, and add timed
may_goto support (Pu Lehui, Kuan-Wei Chiu, Feng Jiang)
- Fix a use-after-free on mm_struct in bpf_find_vma() for foreign
tasks and an mmap_lock leak in the irq_work path (Sanghyun Park)
- Populate mmap-able BPF array map memory lazily which makes mmap()
O(1) instead of proportional to the map size (Song Liu)
- Introduce a jit_required flag and reject programs with inlined
helpers when no JIT is available, where the interpreter would
otherwise jump into an invalid address (Tiezhu Yang)
- Fix the x86 JIT per-CPU address resolution into an extended
register where the REX prefix dropped the high destination register
bit (Vineet Gupta)
- Reject MEM_ALLOC BTF accesses past object bounds, arena frees below
the arena base, and mixed arena and ordinary atomic paths (Yiyang
Chen)
- Fix the trampoline handling of 128-bit arguments and of return
values larger than 8 bytes (Yonghong Song)
- Ensure that any fault prone load is rewritten with exception table
handling, and fix the arena load-acquire and atomic fetch handling
in the x86, arm64, riscv and s390 JITs (Daniel Borkmann)
- Many more fixes and cleanups across the verifier, arena,
trampolines, sockmap, cgroup, ring buffer, x86/arm64/riscv/s390
JITs, libbpf, bpftool, resolve_btfids and selftests"
* tag 'bpf-next-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (373 commits)
selftests/bpf: Add tests for a store on a fault prone qdisc pointer
selftests/bpf: Add tests for fault prone loads out of RCU pointers
selftests/bpf: Add tests for pointer type merge at a shared load
selftests/bpf: Remove duplicate copies of the arena spinlock qnodes
selftests/bpf: Retry stat generation in cgroup_iter_memcg
selftests/bpf: Test pseudo-function policy diagnostics
bpf: Distinguish function references in policy diagnostics
bpf: Preserve source attribution without source text
selftests/bpf: Test kfunc argument diagnostics
bpf: Correct kfunc argument diagnostics
bpf: Use canonical stack argument names in diagnostics
bpf: Preserve R0 lineage across helper calls
selftests/bpf: Exercise negative optlen in cgroup getsockopt hook
bpf: Reject negative optlen in cgroup getsockopt hook
selftests/bpf: tc_tunnel - validate decap GSO and encapsulation state
bpf: Clear decap state on skb_adjust_room shrink path
bpf: Allow new DECAP flags and add guard rails
bpf: Add BPF_F_ADJ_ROOM_DECAP_* flags for tunnel decapsulation
bpf: Refactor masks for ADJ_ROOM flags and encap validation
bpf: Name the enum for BPF_FUNC_skb_adjust_room flags
...
show more ...
|
| #
ce7c9f6c |
| 15-Aug-2026 |
Eduard Zingerman <eddyz87@gmail.com> |
Merge branch 'redesign-verification-errors'
Kumar Kartikeya Dwivedi says:
====================
Redesign Verification Errors
TL;DR: This set reworks verifier error messages to include source and
in
Merge branch 'redesign-verification-errors'
Kumar Kartikeya Dwivedi says:
====================
Redesign Verification Errors
TL;DR: This set reworks verifier error messages to include source and
instruction annotations, together with more causal context, making
failures easier to understand and more actionable when debugging and
repairing BPF programs.
Changelog:
----------
v4 -> v5
v4: https://lore.kernel.org/bpf/20260812233326.3575958-1-memxor@gmail.com
* Defer Verifier Limit reports and the dependent call-chain allocation
guards to follow-up work, reducing the series from 16 to 14 patches.
(Eduard)
* Make kfunc-name disassembly read-only before module-kfunc metadata is
resolved, retain instruction context without usable source metadata,
consolidate its fallback, and restrict source discovery to the containing
subprogram. (Eduard, Sashiko)
* Retain the newest diagnostic history in a bounded 64 MiB rotating buffer,
use absolute logical positions across verifier path switches, report
evicted shared history, and grow storage geometrically. (Eduard)
* Complete active-path history for BPF_LD_IMM64 and atomic fetches, call
clobbers and returns, outgoing stack arguments, legacy packet loads, and
RCU pointer transitions. (Eduard, Sashiko)
* Preserve causal lineage across equal snapshots, nullable pointer-cast
branches, and repeated same-depth function invocations using unique
diagnostic frame identities. Bound each rendered causal path to the oldest
and newest 32 matching events with an omission summary. (Eduard)
* Harden diagnostics for malformed release-kfunc signatures, fixed-size
argument ranges, and dynptr, iterator, memory-size, and required-RCU
failures by reporting the actual offending type or invariant. (Eduard,
Sashiko)
* Remove unrelated formatting and cross-patch churn, dead or single-use
helpers and filter paths, and align helper placement, includes, and commit
descriptions with the patches that first need them. (Eduard)
v3 -> v4
v3: https://lore.kernel.org/bpf/20260713153910.2556007-1-memxor@gmail.com
* Introduce helpers with their first callers and add printf annotations.
(Eduard, Sashiko)
* Remove "report" from diagnostic function names. (Sashiko)
* Reuse bpf_linfo_source and seq_buf, simplify internal names, and use shared
formatting storage. (Eduard)
* Use compact common event fields and record branches at successor entry.
(Eduard)
* Bound event storage at 1 MiB, use kvrealloc(), and drop events non-fatally.
(Eduard, Sashiko)
* Restore diagnostic history only for activated queued states, preserving the
active failure trace during cleanup. (Eduard, Sashiko)
* Record register changes through begin/end and scrub helpers, deriving targets
and origins without caller-saved snapshots. (Eduard)
* Store lineage marks on events and rewind shared formatting storage after
rendering each event. (Eduard)
* Record iterator return values before snapshotting alternate paths. (Sashiko)
* Use the current verifier instruction for global-subprogram dynptr errors.
(Sashiko)
* Use the supplied call name for nullable global-subprogram arguments.
(Sashiko)
* Describe global calls under locks as a verifier restriction rather than a
sleepability failure. (Sashiko)
* Keep diagnostic strings unsplit and put long call openings on their own
line. (Eduard)
* Keep kfunc metadata zeroed before early fetch and allowability failures.
(Sashiko)
* Drop the Verifier Internal Error report patch. (Eduard)
* Distinguish never-initialized registers from invalidated registers.
(local review)
* Preserve the legacy different-lock verifier message. (local review)
* Preserve nullable type qualifiers and stable mismatch formatting.
(local review)
* Mark truncated call chains with an ellipsis. (local review)
v2 -> v3
v2: https://lore.kernel.org/bpf/20260619205934.1312876-1-memxor@gmail.com
* Address various comments from Eduard and Sashiko.
* Move instruction context from a separate gutter into a new section
following source context, since surrounding source lines and BPF
instructions do not map one-to-one.
* Fix active-path branch reconstruction when switching to queued states,
and expand register histories to follow value lineage across spills,
fills, stack reads, helper/kfunc clobbers, and dynptr invalidation.
* Misc improvements and refinements.
v1 -> v2
v1: https://lore.kernel.org/bpf/20260605063412.974640-1-memxor@gmail.com
* Reworked diagnostic history from per-verifier-state log to active
path log with positions saved and reset when verifier search
backtracks. (Eduard)
* Moved reusable diagnostic formatting storage into struct bpf_diag
under struct bpf_verifier_env, and removed large per-report scratch
buffers from verifier stack frames. (Eduard)
* Added stack-slot events so diagnostics follow ordinary stack
spill/fill value flow and invalidations in register-scoped
histories. (Eduard)
* Reused existing source and BTF formatting helpers for diagnostics,
including bpf_get_linfo_file_line() and
btf_type_snprintf_show_name(). (Eduard)
* Fixed diagnostic edge cases around signed offset text,
BPF_MAX_VAR_OFF reporting, negative-offset clamping, poisoned
stack reads, and borrowed-reference invalidations. (Eduard)
* Fixed various miscellaneous diagnostic bugs. (Sashiko)
* Misc improvements and refinements.
---
Motivation
~~~~~~~~~~
The verifier log is the primary interface through which the verifier
communicates to the user its verdict on whether a program was accepted
or rejected.
To aid the debugging of rejection decisions, the verifier also reports
the symbolic state of the program at each instruction, across every explored
path of the BPF program. Such detailed information is critical to
introspect the correctness of verification decisions, and provide
insight into why a given program may have failed to load in the kernel.
A constant pain point in the BPF ecosystem throughout the years has
been the difficulty of debugging verification errors. The human-readable error
messages produced in response to a failure in satisfying safety-related
constraints are often terse, context-dependent, or insufficient for
understanding why a given error may have happened. Users must fall back
to the verbose instruction-by-instruction breakdown of how the symbolic
state evolved to surface the root cause. For programs with a huge log
volume due to high verification complexity, such logs quickly become
inscrutable.
All of this has made life difficult for users lacking an understanding
of how the verifier works, and the various heuristics and idiosyncrasies
used by it. In some cases, even seasoned BPF experts spend significant
time reverse engineering why a program may have failed, and have to
reach into the verifier's source code to form a complete picture of the
verification process.
Such a steep learning curve and cognitive burden also hurts the speed of
BPF development, as the verifier sits right in the middle of the user's
iteration loop while they make use of BPF to solve any given problem.
Expertise in debugging verifier errors does not scale in terms of teams
deploying these programs in production across a diverse set of kernels.
Overall, this leads to a poorer developer experience, causes visible
user dissatisfaction, and remains a drag on wider BPF adoption. With
some of the more recent developments where users increasingly leverage
AI tooling [0] to author their code, this bottleneck becomes even more
critical to address, since it throttles the much faster iteration loop
of AI agents.
[0]: https://lwn.net/Articles/1075067
Approach
~~~~~~~~
This series starts moving selected failures from terse terminal messages
toward diagnostics that carry the relevant context for a verification
failure. The existing verbose log remains the low-level trace. For selected
failures, the new report is emitted after this trace and answers the
immediate debugging questions:
- what verifier rule failed,
- why the current state does not satisfy it,
- where the failing instruction maps to source,
- which earlier branch or state event made this path fail,
- what kind of source change would satisfy the verifier.
The series adds a text-only diagnostics framework under kernel/bpf and
uses it to augment selected verifier errors. Existing verbose(env, ...)
messages are kept, so current selftest expectations and existing log
consumers continue to see the legacy text. The new report has a uniform
outer shape:
Verification failed: <category>: <problem>
Reason:
exact reason for the verification failure, with details
At:
source and instruction annotation
Causal path:
compressed branch and verifier-state events relevant for debugging
Suggestion:
speculation on potential fixes to repair the program
The outer shape is shared, but report construction is category-specific.
The categories are intentionally broad and reviewable. This revision
covers representative cases in Register Type Safety, Memory Safety,
Resource Lifetime Safety, Call Type Safety, Execution Context Safety,
Program Structure and Policy.
It does not attempt to convert every verbose(env, ...) site for now.
Additional verbose-only errors can be moved into the same framework
incrementally.
The following excerpts are copied from this current run on this branch:
./test_progs -j1 \
-a cpumask/test_populate_invalid_destination,\
cpumask/test_alloc_no_release,\
verifier_helper_value_access/via_variable_no_max_check_1,\
verifier_sock/invalidate_pkt_pointers_from_global_func \
-vv
They show the old terminal error and the exact new diagnostic report,
including the source and instruction annotations.
Call Type Safety, cpumask/test_populate_invalid_destination:
Legacy:
R1 type=scalar expected=fp
Diagnostic:
Verification failed: Call Type Safety: Invalid call argument
Reason:
The first argument (R1) to bpf_cpumask_populate does not satisfy the verifier contract: the kfunc
expects 24 bytes of memory for (struct bpf_cpumask), but it is an integer scalar and not
verifier-known memory.
At:
test_populate_invalid_destination @ cpumask_failure.c:234:8
Source context:
232 | ...
233 | ...
>>> 234 | ret = bpf_cpumask_populate(invalid, &bits, sizeof(bits));
| ^-- error: invalid first argument (R1) for bpf_cpumask_populate
235 | if (!ret)
236 | err = 2;
Instruction context:
2 | (b7) r1 = 1193046
3 | (b7) r3 = 8
>>> 4 | (85) call bpf_cpumask_populate#62860
5 | (56) if w0 != 0x0 goto pc+4
6 | (18) r1 = 0xffffc9000028e000
Causal path:
test_populate_invalid_destination @ cpumask_failure.c:234:8
Source context:
232 | ...
233 | ...
>>> 234 | ret = bpf_cpumask_populate(invalid, &bits, sizeof(bits));
| ^-- update: R1 changed from context pointer at offset 0 to integer scalar value
| 1193046
235 | if (!ret)
236 | err = 2;
Instruction context:
0 | (bf) r2 = r10
1 | (07) r2 += -8
>>> 2 | (b7) r1 = 1193046
3 | (b7) r3 = 8
4 | (85) call bpf_cpumask_populate#62860
Suggestion:
Pass stack, map, context, or other verifier-known memory of the expected type and size, not an
integer cast to a pointer.
Register Type Safety, verifier_sock/invalidate_pkt_pointers_from_global_func:
Legacy:
R7 invalid mem access 'scalar'
Diagnostic:
Verification failed: Register Type Safety: Invalid dereference
Reason:
R7 is an integer scalar here, not a pointer to memory.
At:
invalidate_pkt_pointers_from_global_func @ verifier_sock.c:1067:5
Source context:
1065 | ...
1066 | skb_pull_data1(sk, 0);
>>> 1067 | *p = 42; /* this is unsafe */
| ^-- error: invalid dereference of R7 (an integer scalar)
1068 | ...
1069 | }
Instruction context:
8 | (85) call pc+4
9 | (b4) w1 = 42
>>> 10 | (63) *(u32 *)(r7 +0) = r1
11 | (bc) w0 = w6
12 | (95) exit
Causal path:
invalidate_pkt_pointers_from_global_func @ verifier_sock.c:1062:29
Source context:
1060 | int invalidate_pkt_pointers_from_global_func(struct __sk_buff *sk)
1061 | ...
>>> 1062 | int *p = (void *)(long)sk->data;
| ^-- update: R7 changed from uninitialized value to pkt at offset 0
1063 | ...
1064 | if ((void *)(p + 1) > (void *)(long)sk->data_end)
Instruction context:
0 | (b4) w6 = 2
1 | (61) r2 = *(u32 *)(r1 +80)
>>> 2 | (61) r7 = *(u32 *)(r1 +76)
3 | (bf) r3 = r7
4 | (07) r3 += 4
invalidate_pkt_pointers_from_global_func @ verifier_sock.c:1064:22
Source context:
1062 | int *p = (void *)(long)sk->data;
1063 | ...
>>> 1064 | if ((void *)(p + 1) > (void *)(long)sk->data_end)
| ^-- branch: took the false branch of this conditional, goto not followed
1065 | ...
1066 | skb_pull_data1(sk, 0);
Instruction context:
3 | (bf) r3 = r7
4 | (07) r3 += 4
>>> 5 | (2d) if r3 > r2 goto pc+5
6 | (b4) w6 = 0
7 | (b4) w2 = 0
invalidate_pkt_pointers_from_global_func @ verifier_sock.c:1066:2
Source context:
1064 | if ((void *)(p + 1) > (void *)(long)sk->data_end)
1065 | ...
>>> 1066 | skb_pull_data1(sk, 0);
| ^-- invalidated: R7: packet data may have moved; previous value was pkt at
| offset 0
1067 | *p = 42; /* this is unsafe */
1068 | ...
Instruction context:
6 | (b4) w6 = 0
7 | (b4) w2 = 0
>>> 8 | (85) call pc+4
9 | (b4) w1 = 42
10 | (63) *(u32 *)(r7 +0) = r1
Suggestion:
Preserve a pointer-valued register where needed, or reload and revalidate the pointer after scalar
arithmetic, helper calls, or other operations that can invalidate it.
Memory Safety, verifier_helper_value_access/via_variable_no_max_check_1:
Legacy:
R1 unbounded memory access, make sure to bounds check any such access
Diagnostic:
Verification failed: Memory Safety: Access outside bounds
Reason:
The verifier cannot prove offset + access_size <= object_size. Here, the maximal bound for a
memory access is 4294967295 and exceeds maximum allowed offset of 536870912. R1 is map_value;
offset is variable: known bits 0x0, unknown mask 0xffffffff; signed range [0, 4294967295],
unsigned range [0, 4294967295]; access_size is 1; object_size is 48.
At:
via_variable_no_max_check_1 @ verifier_helper_value_access.c:627:2
Source context:
625 | ...
626 | ...
>>> 627 | asm volatile (" \
| ^-- error: access may be outside object bounds
628 | ...
629 | ...
Instruction context:
11 | (b7) r2 = 1
12 | (b7) r3 = 0
>>> 13 | (85) call bpf_probe_read_kernel#113
14 | (95) exit
Causal path:
via_variable_no_max_check_1 @ verifier_helper_value_access.c:627:2
Source context:
625 | ...
626 | ...
>>> 627 | asm volatile (" \
| ^-- update: R0 changed from uninitialized value to nullable map value from
| map_hash_48b at offset 0
628 | ...
629 | ...
Instruction context:
4 | (18) r1 = 0xffff88810a3ea000
>>> 6 | (85) call bpf_map_lookup_elem#1
7 | (15) if r0 == 0x0 goto pc+6
8 | (bf) r1 = r0
via_variable_no_max_check_1 @ verifier_helper_value_access.c:627:2
Source context:
625 | ...
626 | ...
>>> 627 | asm volatile (" \
| ^-- branch: took the false branch of this conditional, goto not followed
628 | ...
629 | ...
Instruction context:
6 | (85) call bpf_map_lookup_elem#1
>>> 7 | (15) if r0 == 0x0 goto pc+6
8 | (bf) r1 = r0
9 | (61) r3 = *(u32 *)(r0 +0)
via_variable_no_max_check_1 @ verifier_helper_value_access.c:627:2
Source context:
625 | ...
626 | ...
>>> 627 | asm volatile (" \
| ^-- update: R1 changed from uninitialized value to map value from map_hash_48b
| at offset 0
628 | ...
629 | ...
Instruction context:
6 | (85) call bpf_map_lookup_elem#1
7 | (15) if r0 == 0x0 goto pc+6
>>> 8 | (bf) r1 = r0
9 | (61) r3 = *(u32 *)(r0 +0)
10 | (0f) r1 += r3
via_variable_no_max_check_1 @ verifier_helper_value_access.c:627:2
Source context:
625 | ...
626 | ...
>>> 627 | asm volatile (" \
| ^-- update: R1 changed from map value from map_hash_48b at offset 0 to map value
| from map_hash_48b with variable offset: known bits 0x0, unknown mask
| 0xffffffff, signed range [0, 4294967295], unsigned range [0, 4294967295]
628 | ...
629 | ...
Instruction context:
8 | (bf) r1 = r0
9 | (61) r3 = *(u32 *)(r0 +0)
>>> 10 | (0f) r1 += r3
11 | (b7) r2 = 1
12 | (b7) r3 = 0
Suggestion:
Add or adjust a bounds check that proves offset + access_size stays within the object.
Resource Lifetime Safety, cpumask/test_alloc_no_release:
Legacy:
Unreleased reference id=2 alloc_insn=0
BPF_EXIT instruction in main prog would lead to reference leak
Diagnostic:
Verification failed: Resource Lifetime Safety: Unreleased resource
Reason:
Owned resource (id=2) was acquired at instruction 0 and still needs to be released before this
exit path.
At:
test_alloc_no_release @ cpumask_failure.c:36:5
Source context:
34 | ...
35 | ...
>>> 36 | int BPF_PROG(test_alloc_no_release, struct task_struct *task, u64 clone_flags)
| ^-- error: owned resource (id=2) still needs release
37 | ...
38 | ...
Instruction context:
19 | (7b) *(u64 *)(r10 -8) = r6
20 | (b4) w0 = 0
>>> 21 | (95) exit
Causal path:
test_alloc_no_release @ cpumask_common.h:78:12
Source context:
76 | ...
77 | ...
>>> 78 | cpumask = bpf_cpumask_create();
| ^-- acquired: owned resource (id=2)
79 | if (!cpumask) {
80 | err = 1;
Instruction context:
>>> 0 | (85) call bpf_cpumask_create#62851
1 | (bf) r6 = r0
2 | (55) if r6 != 0x0 goto pc+5
test_alloc_no_release @ cpumask_common.h:79:6
Source context:
77 | ...
78 | cpumask = bpf_cpumask_create();
>>> 79 | if (!cpumask) {
| ^-- branch: took the true branch of this conditional, goto followed
80 | err = 1;
81 | ...
Instruction context:
0 | (85) call bpf_cpumask_create#62851
1 | (bf) r6 = r0
>>> 2 | (55) if r6 != 0x0 goto pc+5
3 | (18) r1 = 0xffffc90000252000
test_alloc_no_release @ cpumask_common.h:84:6
Source context:
82 | ...
83 | ...
>>> 84 | if (!bpf_cpumask_empty(cast(cpumask))) {
| ^-- branch: took the true branch of this conditional, goto followed
85 | err = 2;
86 | bpf_cpumask_release(cpumask);
Instruction context:
9 | (85) call bpf_cpumask_empty#62852
10 | (54) w0 &= 1
>>> 11 | (56) if w0 != 0x0 goto pc+7
12 | (18) r1 = 0xffffc90000252000
Suggestion:
Release or transfer ownership of the acquired resource on every path before the program exits.
Patch layout:
- Patches 1-2 add the initial renderer, source-line lookup, and separate
source and instruction context blocks. Reusable report sections arrive with their first
category-specific consumers.
- Patches 3-7 add bounded, growable environment-owned diagnostic
history. It grows to 64 MiB and then retains the newest events in a
rotating buffer. The history follows the active verifier path and is
pruned when backtracking; it records branch outcomes, material register
changes, reference lifetime events, and execution-context events so
reports can explain the path and causal state transitions that led to
the failure.
- Patches 8-14 add the first category-specific reports. These patches
hook selected verifier failure sites and choose the evidence that is
useful for that error class.
Evaluation
~~~~~~~~~~
The evaluation below is retained from v4 while v5 changes are in progress.
It includes two Verifier Limit cases removed from v5 and must be refreshed
before posting.
To quantitatively assess diagnostic quality beyond subjective human
feedback, we use AI models (called over APIs) and veristat metrics to
compare results.
Models are used as a way to measure repair utility of the extra
diagnostics over a fixed test set. Each prompt contains only a sanitized
source snippet and either the legacy verifier log or the new diagnostic
log. To avoid leaking the answer through the test itself, comments,
annotations, and other source hints that describe the intended failure
were removed. The model is not given internet access, repository access,
test execution, verifier access, or the expected fix. The expected
causes and intended repairs are kept outside the prompt. Under those
constraints, correctness, exact repair rate, output size, reasoning
tokens, cost, and wall time provide a proxy for whether the additional
verifier context makes the failure easier to understand and turn into a
source-level fix.
Verifier cost is assessed by forcing the collection of diagnostics
information during normal verification. By default, this information is
collected and processed only when verbose logs are enabled, but forcing
it even without a verbose log helps us measure the CPU time and memory
cost of the extra data.
Both evaluations are covered in the sections below.
Repair Quality
--------------
Repair quality is measured by asking API-only models to propose source
fixes from a sanitized source snippet and verifier log. The criterion is
score >= 3 on a 0-4 local grading scale, where 3 means a likely fix with
incomplete detail and 4 means an actionable source-level fix. Score 4 is
reported separately as the exact repair rate. The reported model set
contains 596 completed API responses: 298 diagnostic and 298 legacy.
Main results (details available in Appendix):
Metric Diagnostic Legacy Delta
---------------------------------- ----------- ----------- --------
Answers 298 298
Success rate 97.0% 97.3% -0.3 pp
Exact repair rate 82.2% 72.1% +10.1 pp
Mean score 3.79 3.69 +0.10
Solver cost $8.93 $10.37 -13.8%
Mean output tokens per answer 1662 1975 -15.8%
Mean reasoning tokens per answer 951 1080 -11.9%
Mean wall time per answer 37.3s 44.1s -15.4%
Diagnostic prompts carry more input context. The resulting answers are
still shorter and cheaper. In this run, diagnostics do not materially
change the coarse success rate, but they increase exact repairs by 10.1
percentage points while reducing cost, output tokens, reasoning tokens,
and wall time.
Verifier cost
-------------
Verifier cost is measured with veristat over the BPF selftest programs
selected by tools/testing/selftests/bpf/veristat.cfg, with five
repetitions per configuration. With diagnostics gated by log level, wall
time and verifier duration stay close to baseline. Forcing diagnostics
on for every verifier run adds modest overhead on this workload.
memory.peak is measured with cgroup v2 memory accounting for each
program load. The table reports the mean wall time, the mean summed
verifier duration, and the mean of the per-repetition maximum
memory.peak values.
Configuration Wall time mean Verifier duration memory.peak
---------------------------- -------------- ----------------- -----------
bpf-next baseline 25.78s 9.86s 142 MiB
diagnostics, gated 26.64s 10.16s 144 MiB
diagnostics, forced on 28.01s 11.00s 148 MiB
TODO
~~~~
Known follow-up work:
- Convert more verbose-only verifier errors into category-specific
reports.
- Integrate loop-convergence failure summarization from Eduard.
- Report candidate kfuncs/helpers for releasing owned resources.
- Explore association of source variables with verifier registers
where debug info permits it.
- Refine suggestions per category and, where useful, link diagnostics
to maintained documentation.
- Bring verifier warnings into the same reporting framework.
Appendix: AI repair details
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 20 verifier-failing selftest cases are:
Case Diff Category Selftest selector
------- ------ -------------------------- ---------------------------------------------
case-001 easy Call Type Safety cpumask/test_populate_invalid_destination
case-002 easy Resource Lifetime Safety cpumask/test_alloc_no_release
case-003 easy Register Type Safety verifier_spill_fill/check_corrupted_spill_fill
case-004 easy Register Type Safety test_global_funcs/global_func12
case-005 easy Execution Context Safety preempt_lock/preempt_sleepable_helper
case-006 easy Policy verifier_helper_restricted/in_bpf_prog_type_kprobe_1
case-007 medium Memory Safety dynptr/dynptr_slice_var_len1
case-008 medium Call Type Safety dynptr/test_dynptr_skb_small_buff
case-009 medium Call Type Safety task_kfunc/task_kfunc_acquire_untrusted
case-010 medium Register Type Safety test_global_funcs/global_func6
case-011 medium Resource Lifetime Safety dynptr/ringbuf_missing_release2
case-012 medium Execution Context Safety irq/irq_sleepable_helper_global_subprog
case-013 medium Verifier Limit test_global_funcs/global_func1
case-014 hard Memory Safety verifier_helper_value_access/via_variable_no_max_check_1
case-015 hard Register Type Safety verifier_sock/invalidate_pkt_pointers_from_global_func
case-016 hard Resource Lifetime Safety verifier_ref_tracking/check_free_in_one_subbranch
case-017 hard Resource Lifetime Safety irq/irq_restore_ooo
case-018 hard Resource Lifetime Safety res_spin_lock_failure/res_spin_lock_ooo_unlock
case-019 hard Program Structure verifier_loops1/bounded_recursion
case-020 hard Verifier Limit verifier_liveness_exp/liveness_exponential_complexity
The grading scale is:
- 4: identifies the verifier cause and gives an actionable source-level fix.
- 3: gives a likely fix, but with incomplete explanation or detail.
- 2: identifies part of the issue, but not enough to fix confidently.
- 1: gives only a broad verifier-area answer, or a wrong/insufficient fix.
- 0: does not identify the intended verifier failure.
Detailed effort metrics for the model set:
Metric Variant Mean Median P99
----------------------- ---------- -------- -------- --------
Cost per answer diagnostic $0.030 $0.019 $0.203
Cost per answer legacy $0.035 $0.018 $0.223
Input tokens diagnostic 1391 1220 4048
Input tokens legacy 1052 805 3655
Output tokens diagnostic 1662 954 8680
Output tokens legacy 1975 1034 9912
Reasoning tokens diagnostic 951 208 8108
Reasoning tokens legacy 1080 228 6322
Wall time diagnostic 37.3s 18.3s 222.7s
Wall time legacy 44.1s 19.8s 255.5s
Per-model results for diagnostic prompts:
Model profile Ans Succ Exact Mean Cost OutK ReasK Wall
----------------------------------------- --- ----- ----- ---- ------- ---- ----- -----
anthropic-haiku-4.5-default 20 90.0 80.0 3.70 $0.087 11.4 0.0 5.0s
anthropic-opus-4.8-high 20 100.0 90.0 3.90 $0.819 25.5 0.0 15.5s
anthropic-opus-4.8-medium 20 95.0 90.0 3.85 $0.870 27.5 0.0 12.7s
anthropic-sonnet-4.6-high 20 95.0 80.0 3.75 $0.824 48.9 0.0 21.6s
anthropic-sonnet-4.6-medium 20 100.0 65.0 3.65 $0.278 12.4 0.0 6.6s
openai-gpt-5.3-codex-high 20 100.0 80.0 3.80 $0.601 39.8 33.9 25.0s
openai-gpt-5.3-codex-medium 20 95.0 85.0 3.80 $0.287 17.5 11.4 13.5s
openai-gpt-5.5-high 20 100.0 90.0 3.90 $2.356 74.4 65.2 56.8s
openai-gpt-5.5-low 20 100.0 90.0 3.90 $0.686 18.7 8.5 21.3s
openai-gpt-5.5-medium 19 100.0 84.2 3.84 $1.353 41.1 31.8 37.4s
openai-gpt-5.5-none 20 95.0 90.0 3.85 $0.457 11.1 0.0 10.4s
openrouter-deepseek-r1-0528 20 100.0 75.0 3.75 $0.145 61.5 53.8 98.3s
openrouter-deepseek-v3.2 19 100.0 78.9 3.79 $0.028 64.2 58.1 87.3s
openrouter-glm-5.1-high 20 95.0 80.0 3.75 $0.113 28.8 20.7 19.3s
openrouter-qwen3-coder 20 90.0 75.0 3.65 $0.028 12.4 0.0 7.1s
Per-model results for legacy prompts:
Model profile Ans Succ Exact Mean Cost OutK ReasK Wall
----------------------------------------- --- ----- ----- ---- ------- ---- ----- -----
anthropic-haiku-4.5-default 20 90.0 45.0 3.35 $0.081 11.6 0.0 5.0s
anthropic-opus-4.8-high 20 90.0 70.0 3.60 $1.192 42.2 0.0 17.5s
anthropic-opus-4.8-medium 20 95.0 85.0 3.80 $1.001 34.5 0.0 13.4s
anthropic-sonnet-4.6-high 20 100.0 75.0 3.75 $1.181 74.1 0.0 24.4s
anthropic-sonnet-4.6-medium 20 95.0 65.0 3.60 $0.420 23.4 0.0 12.3s
openai-gpt-5.3-codex-high 20 100.0 85.0 3.85 $0.562 37.8 31.6 27.1s
openai-gpt-5.3-codex-medium 20 100.0 75.0 3.75 $0.318 20.3 13.7 13.6s
openai-gpt-5.5-high 19 100.0 78.9 3.79 $2.613 84.0 75.4 98.1s
openai-gpt-5.5-low 20 100.0 75.0 3.75 $0.664 19.0 9.7 21.7s
openai-gpt-5.5-medium 20 100.0 75.0 3.75 $1.602 50.2 41.0 56.1s
openai-gpt-5.5-none 20 95.0 85.0 3.80 $0.416 10.7 0.0 10.9s
openrouter-deepseek-r1-0528 20 95.0 70.0 3.65 $0.149 64.6 57.5 92.5s
openrouter-deepseek-v3.2 20 100.0 60.0 3.60 $0.030 74.3 67.8 98.3s
openrouter-glm-5.1-high 19 100.0 63.2 3.63 $0.115 32.1 24.9 30.4s
openrouter-qwen3-coder 20 100.0 75.0 3.75 $0.022 9.5 0.0 5.4s
====================
Link: https://patch.msgid.link/20260815064612.378577-1-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
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