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[bpf-next,v3,0/3] fixes for concurrent htab updates

Message ID 20220829023709.1958204-1-houtao@huaweicloud.com (mailing list archive)
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Series fixes for concurrent htab updates | expand

Message

Hou Tao Aug. 29, 2022, 2:37 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

Hi,

The patchset aims to fix the issues found during investigating the
syzkaller problem reported in [0]. It seems that the concurrent updates
to the same hash-table bucket may fail as shown in patch 1.

Patch 1 uses preempt_disable() to fix the problem for
htab_use_raw_lock() case. For !htab_use_raw_lock() case, the problem is
left to "BPF specific memory allocator" patchset [1] in which
!htab_use_raw_lock() will be removed.

Patch 2 fixes the out-of-bound memory read problem reported in [0]. The
problem has the root cause as patch 1 and it is fixed by handling -EBUSY
from htab_lock_bucket() correctly.

Patch 3 add two cases for hash-table update: one for the reentrancy of
bpf_map_update_elem(), and another one for concurrent updates of the
same hash-table bucket.

Comments are always welcome.

Regards,
Tao

[0]: https://lore.kernel.org/bpf/CACkBjsbuxaR6cv0kXJoVnBfL9ZJXjjoUcMpw_Ogc313jSrg14A@mail.gmail.com/
[1]: https://lore.kernel.org/bpf/20220819214232.18784-1-alexei.starovoitov@gmail.com/

Change Log:

v3:
 * patch 1: update commit message and add Fixes tag
 * patch 2: add Fixes tag
 * patch 3: elaborate the description of test cases

v2: https://lore.kernel.org/bpf/bd60ef93-1c6a-2db2-557d-b09b92ad22bd@huaweicloud.com/
 * Note the fix is for CONFIG_PREEMPT case in commit message and add
   Reviewed-by tag for patch 1
 * Drop patch "bpf: Allow normally concurrent map updates for !htab_use_raw_lock() case"
 * Add two test cases for htab updates

v1: https://lore.kernel.org/bpf/20220821033223.2598791-1-houtao@huaweicloud.com/

Hou Tao (3):
  bpf: Disable preemption when increasing per-cpu map_locked
  bpf: Propagate error from htab_lock_bucket() to userspace
  selftests/bpf: add test cases for htab update

 kernel/bpf/hashtab.c                          |  30 ++++-
 .../selftests/bpf/prog_tests/htab_update.c    | 126 ++++++++++++++++++
 .../testing/selftests/bpf/progs/htab_update.c |  29 ++++
 3 files changed, 178 insertions(+), 7 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/htab_update.c
 create mode 100644 tools/testing/selftests/bpf/progs/htab_update.c