[PATCH bpf-next v2 0/2] bpf: fix the crash caused by task iterators over vma

[Kui-Feng Lee <kuifeng@meta.com>]

This issue is related to task iterators over vma. A system crash can
occur when a task iterator travels through vma of tasks as the death
of a task will clear the pointer to its mm, even though the
task_struct is still held. As a result, an unexpected crash happens
due to a null pointer. To address this problem, a reference to mm is
kept on the iterator to make sure that the pointer is always
valid. This patch set provides a solution for this crash by properly
referencing mm on task iterators over vma.

The major changes from v1 are:

 - Fix commit logs of the test case.

 - Use reverse Christmas tree coding style.

 - Remove unnecessary error handling for time().

v1: https://lore.kernel.org/bpf/20221216015912.991616-1-kuifeng@meta.com/

Kui-Feng Lee (2):
  bpf: keep a reference to the mm, in case the task is dead.
  selftests/bpf: add a test for iter/task_vma for short-lived processes

 kernel/bpf/task_iter.c                        | 39 +++++++---
 .../selftests/bpf/prog_tests/bpf_iter.c       | 73 +++++++++++++++++++
 2 files changed, 100 insertions(+), 12 deletions(-)

-- 
2.30.2