[v5,0/4] kasan: memorize and print call_rcu stack

Message

Walter Wu May 20, 2020, 12:32 p.m. UTC

This patchset improves KASAN reports by making them to have
call_rcu() call stack information. It is useful for programmers
to solve use-after-free or double-free memory issue.

The KASAN report was as follows(cleaned up slightly):

BUG: KASAN: use-after-free in kasan_rcu_reclaim+0x58/0x60

Freed by task 0:
 kasan_save_stack+0x24/0x50
 kasan_set_track+0x24/0x38
 kasan_set_free_info+0x18/0x20
 __kasan_slab_free+0x10c/0x170
 kasan_slab_free+0x10/0x18
 kfree+0x98/0x270
 kasan_rcu_reclaim+0x1c/0x60

Last one call_rcu() call stack:
 kasan_save_stack+0x24/0x50
 kasan_record_aux_stack+0xbc/0xd0
 call_rcu+0x8c/0x580
 kasan_rcu_uaf+0xf4/0xf8

Generic KASAN will record the last two call_rcu() call stacks and
print up to 2 call_rcu() call stacks in KASAN report. it is only
suitable for generic KASAN.

This feature considers the size of struct kasan_alloc_meta and
kasan_free_meta, we try to optimize the structure layout and size
, let it get better memory consumption.

[1]https://bugzilla.kernel.org/show_bug.cgi?id=198437
[2]https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack$20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ

Changes since v2:
- remove new config option, default enable it in generic KASAN
- test this feature in SLAB/SLUB, it is pass.
- modify macro to be more clearly
- modify documentation

Changes since v3:
- change recording from first/last to the last two call stacks
- move free track into kasan free meta
- init slab_free_meta on object slot creation
- modify documentation

Changes since v4:
- change variable name to be more clearly
- remove the redundant condition
- remove init free meta-data and increasing object condition

Changes since v5:
- add a macro KASAN_KMALLOC_FREETRACK in order to check whether
  print free stack
- change printing message
- remove descriptions in Kocong.kasan

Walter Wu (4):
rcu/kasan: record and print call_rcu() call stack
kasan: record and print the free track
kasan: add tests for call_rcu stack recording
kasan: update documentation for generic kasan

Documentation/dev-tools/kasan.rst |  3 +++
include/linux/kasan.h             |  2 ++
kernel/rcu/tree.c                 |  2 ++
lib/test_kasan.c                  | 30 ++++++++++++++++++++++++++++++
mm/kasan/common.c                 | 26 ++++----------------------
mm/kasan/generic.c                | 43 +++++++++++++++++++++++++++++++++++++++++++
mm/kasan/generic_report.c         |  1 +
mm/kasan/kasan.h                  | 23 +++++++++++++++++++++--
mm/kasan/quarantine.c             |  1 +
mm/kasan/report.c                 | 50 ++++++++++++++++++++++++++++----------------------
mm/kasan/tags.c                   | 37 +++++++++++++++++++++++++++++++++++++
11 files changed, 172 insertions(+), 46 deletions(-)