[PATCH v2 00/10] rcu: Improve callback diagnostics and validation

[Kunwu Chan <kunwu.chan@gmail.com>]

Hi,

This series improves callback diagnostics and validation across RCU,
SRCU, and RCU Tasks.

Patches 1-3 record callback registration stacks for KASAN in Tree
SRCU, Tiny SRCU, and Tiny RCU.  KASAN prints the recorded auxiliary
stack when reporting a use-after-free.

Patches 4-6 add rcu_head alignment and NULL callback-function checks.

Patches 7-10 detect duplicate callback enqueue attempts before
queueing, using the RCU head debug-object mechanism.  A duplicate
registration is rejected at entry and __ratelimit() controls the
diagnostic output group (pr_err, mem_dump_obj, dump_stack).
Detection requires CONFIG_DEBUG_OBJECTS_RCU_HEAD.

Changes since v1:
- Patches 7-9: __ratelimit() + dump_stack() instead of hard-coded limit
- Patch 10 (new): same change for Tree RCU's rcu_do_enqueue()
- Patch 9: fixed log format to avoid pseudo-function names
- Tags: Reviewed-by (4-6), Suggested-by (7-10)
- v1: https://lore.kernel.org/all/20261023101841.2910719-1-kunwu.chan@gmail.com/


Testing:
  rcutorture with KASAN (SRCU-N, SRCU-P, SRCU-T, SRCU-U, TINY01,
  TINY02, TREE03, 3min each): all exitcode 0.

  KASAN aux stack (QEMU, CONFIG_KASAN_GENERIC=y):
    Last potentially related work creation:
     kasan_save_stack+0x33/0x60
     kasan_record_aux_stack+0x8c/0xa0
     call_srcu+0xb2/0x390

  Duplicate enqueue (QEMU, CONFIG_DEBUG_OBJECTS_RCU_HEAD=y):
    call_srcu(): Duplicate call_srcu() CB ... ->cb
    dump_stack_lvl+0x47/0x60
    call_rcu_tasks_generic(): Duplicate CB for RCU Tasks, ... ->cb
    dump_stack_lvl+0x47/0x60
    rcu_do_enqueue(): Double-freed CB ... ->cb  slab kmalloc-16 ...


Kunwu Chan (10):
  srcu: Record callback registration stack for KASAN
  srcutiny: Record callback registration stack for KASAN
  rcu: Record callback registration stack for Tiny RCU
  srcu: Validate callback arguments
  rcu: Validate callback arguments in Tiny RCU
  rcu-tasks: Validate callback arguments
  srcu: Detect duplicate callback enqueue at registration
  srcutiny: Detect duplicate callback enqueue
  rcu-tasks: Detect duplicate callback enqueue
  rcu: Improve duplicate callback diagnostics

 kernel/rcu/srcutiny.c | 34 ++++++++++++++++++++++++++++++++++
 kernel/rcu/srcutree.c | 36 ++++++++++++++++++++++++++++++------
 kernel/rcu/tasks.h    | 27 +++++++++++++++++++++++++++
 kernel/rcu/tiny.c     | 11 +++++++++++
 kernel/rcu/tree.c     |  9 +++++++--
 5 files changed, 109 insertions(+), 8 deletions(-)


base-commit: 940793b926aa94bf65ec404043050888e3053188
-- 
2.43.0