Refactor object relationship tracking in the verifier and fix a dynptr
use-after-free bug where file/skb dynptrs are not invalidated when the
parent referenced object is freed.

Add parent_id to bpf_reg_state to precisely track child-parent
relationships. A child object's parent_id points to the parent object's
id. This replaces the PTR_TO_MEM-specific dynptr_id.

Remove ref_obj_id from bpf_reg_state by folding its role into the
existing id field. Previously, id tracked pointer identity for null
checking while ref_obj_id tracked the owning reference for lifetime
management. These are now unified: acquire helpers and kfuncs set id
to the acquired reference id, and release paths use id directly.

Add reg_is_referenced() which checks if a register is referenced by
looking up its id in the reference array. This replaces all former
ref_obj_id checks.

For release_reference(), invalidating an object now also invalidates
all descendants by traversing the object tree. This is done using
stack-based DFS to avoid recursive call chains of release_reference() ->
unmark_stack_slots_dynptr() -> release_reference(). Referenced objects
encountered during tree traversal are reported as leaked references.

Add parent_id to bpf_reference_state to enable hierarchical reference
tracking. When acquiring a reference, a parent_id can be specified to
link the new reference to an existing one (e.g., referenced dynptrs
acquire a reference with parent_id linking to the parent object's
reference).

Pointer casting:

For pointer casting helpers (bpf_sk_fullsock, bpf_tcp_sock), instead of
propagating ref_obj_id, the cast result reuses the same reference id as
the source pointer. Since the cast may return NULL for a non-NULL input,
the NULL case is explored as a separate verifier branch. This allows
releasing any of the original or cast pointers to invalidate all others.

Referenced dynptrs:

When constructing a referenced dynptr, acquire a intermediate reference
with parent_id linking to the parent referenced object. The dynptr and
all clones share the same parent_id (pointing to the intermediate ref)
but get unique ids for independent slice tracking. Releasing a
referenced dynptr releases the parent reference, which in turn
invalidates all clones and their derived slices.

Owning to non-owning reference conversion:

After converting owning to non-owning by clearing id (e.g.,
object(id=1) -> object(id=0)), the verifier releases the reference
state via release_reference_nomark().

Note that the error message "reference has not been acquired before" in
the helper and kfunc release paths is removed. This message was already
unreachable. The verifier only calls release_reference() after
confirming the reference is valid, so the condition could never trigger
in practice.

Fixes: 870c28588afa ("bpf: net_sched: Add basic bpf qdisc kfuncs")
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-6-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Many BPF_MAP_CREATE validation failures currently return -EINVAL without
any explanation to userspace.

Plumb common syscall log attributes into map_create(), create a verifier
log from bpf_common_attr::log_buf/log_size/log_level, and report
map-creation failure reasons through that buffer.

This improves debuggability by allowing userspace to inspect why map
creation failed and read back log_true_size from common attributes.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260512153157.28382-7-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

BPF_PROG_LOAD can now take log parameters from both union bpf_attr and
struct bpf_common_attr. The merge rules are:

- if both sides provide a complete log tuple (buf/size/level) and they
  match, use it;
- if only one side provides log parameters, use that one;
- if both sides provide complete tuples but they differ, return -EINVAL.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260512153157.28382-5-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

The next commit will add support for reporting logs via extended common
attributes, including 'log_true_size'.

To prepare for that, refactor the 'log_true_size' reporting logic by
introducing a new struct bpf_log_attr to encapsulate log-related behavior:

 * bpf_log_attr_init(): initialize log fields, which will support
   extended common attributes in the next commit.
 * bpf_log_attr_finalize(): handle log finalization and write back
   'log_true_size' to userspace.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260512153157.28382-4-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Replace direct access to bpf_reg_state->{smin,smax,umin,umax,
s32_min,s32_max,u32_min,u32_max}_value with getter/setter inline
functions, preparing for future switch to cnum-based internal
representation.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260424-cnums-everywhere-rfc-v1-v3-2-ca434b39a486@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

As a sanity check poison stack slots that stack liveness determined
to be dead, so that any read from such slots will cause program rejection.
If stack liveness logic is incorrect the poison can cause
valid program to be rejected, but it also will prevent unsafe program
to be accepted.

Allow global subprogs "read" poisoned stack slots.
The static stack liveness determined that subprog doesn't read certain
stack slots, but sizeof(arg_type) based global subprog validation
isn't accurate enough to know which slots will actually be read by
the callee, so it needs to check full sizeof(arg_type) at the caller.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-14-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Namely:
- bpf_subprog_is_global
- bpf_vlog_alignment

Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-1-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Move find_linfo() as bpf_find_linfo() into core.c to allow for its use
in the verifier in subsequent patches.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20260408021359.3786905-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This field is now used only for linked scalar registers tracking.
Rename it to 'delta' to better describe it's purpose:
constant delta between "linked" scalars with the same ID.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260212-ptrs-off-migration-v2-4-00820e4d3438@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This commit consolidates static and varying pointer offset tracking
logic. All offsets are now represented solely using `.var_off` and
min/max fields. The reasons are twofold:
- This simplifies pointer tracking code, as each relevant function
  needs to check the `.var_off` field anyway.
- It makes it easier to widen pointer registers for the purpose of loop
  convergence checks, by forgoing the `regsafe()` logic demanding
  `.off` fields to be identical.

The changes are spread across many functions and are hard to group
into smaller patches. Some of the logical changes include:
- Checks in __check_ptr_off_reg() are reordered so that the
  tnum_is_const() check is done before operating on reg->var_off.value.
- check_packet_access() now uses check_mem_region_access() to handle
  possible 'off' overflow cases.
- In check_helper_mem_access() utility functions like
  check_packet_access() are now called with 'off=0', as these utility
  functions now account for the complete register offset range.
- In check_reg_type() a call to __check_ptr_off_reg() is added before
  a call to btf_struct_ids_match(). This prevents
  btf_struct_ids_match() from potentially working on non-constant
  reg->var_off.value.
- regsafe() is relaxed to avoid comparing '.off' field for pointers.

As a precaution, the changes are verified in [1] by adding a pass
checking that no pointer has non-zero '.off' field on each
do_check_insn() iteration.

[1] https://github.com/eddyz87/bpf/tree/ptrs-off-migration

Notable selftests changes:
- `.var_off` value changed because it now combines static and varying
  offsets. Affected tests:
  - linked_list/incorrect_node_var_off
  - linked_list/incorrect_head_var_off2
  - verifier_align/packet_variable_offset

- Overflowing `smax_value` bound leads to a pointer with big negative
  or positive offset to be rejected immediately (previously overflowing
  `rX += const` instruction updated `.off` field avoiding the overflow).
  Affected tests:
  - verifier_align/dubious_pointer_arithmetic
  - verifier_bounds/var_off_insn_off_test1

- Invalid access to packet now reports full offset inside a packet.
  Affected tests:
  - verifier_direct_packet_access/test23_x_pkt_ptr_4

- A change in check_mem_region_access() behavior:
  when register `.smin_value` is negative, it reports
  "rX min value is negative..." before calling into __check_mem_access()
  which reports "invalid access to ...".
  In the tests below, the `.off` field was negative, while `.smin_value`
  remained positive. This is no longer the case after the changes in
  this commit. Affected tests:
  - verifier_gotox/jump_table_invalid_mem_acceess_neg
  - verifier_helper_packet_access/test15_cls_helper_fail_sub
  - verifier_helper_value_access/imm_out_of_bound_2
  - verifier_helper_value_access/reg_out_of_bound_2
  - verifier_meta_access/meta_access_test2
  - verifier_value_ptr_arith/known_scalar_from_different_maps
  - lower_oob_arith_test_1
  - value_ptr_known_scalar_3
  - access_value_ptr_known_scalar

- Usage of check_mem_region_access() instead of __check_mem_access()
  in check_packet_access() changes the reported message from
  "rX offset is outside ..." to "rX min/max value is outside ...".
  Affected tests:
  - verifier_xdp_direct_packet_access/*

- In check_func_arg_reg_off() the check for zero offset now operates
  on `.var_off` field instead of `.off` field. For tests where the
  pattern looks like `kfunc(reg_with_var_off, ...)`, this changes the
  reported error:
  - previously the error "variable ... access ... disallowed"
    was reported by __check_ptr_off_reg();
  - now "R1 must have zero offset ..." is reported by
    check_func_arg_reg_off() itself.
  Affected tests:
  - verifier/calls.c
    "calls: invalid kfunc call: PTR_TO_BTF_ID with variable offset"

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260212-ptrs-off-migration-v2-2-00820e4d3438@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>