[PATCH bpf-next 0/9] bpf: Avoid unnecessary deadlock detection and failure in task storage

Martin KaFai Lau
2022-10-25T18:46:12Z

The commit bc235cdb423a ("bpf: Prevent deadlock from recursive bpf_task_storage_[get|delete]")
added deadlock detection to avoid a tracing program from recurring
on the bpf_task_storage_{get,delete}() helpers. These helpers acquire
a spin lock and it will lead to deadlock.

It is unnecessary for the bpf_lsm and bpf_iter programs which do
not recur. The situation is the same as the existing
bpf_pid_task_storage_{lookup,delete}_elem() which are
used in the syscall and they also do not have deadlock detection.

This set is to add new bpf_task_storage_{get,delete}() helper proto
without the deadlock detection. The set also removes the prog->active
check from the bpf_lsm and bpf_iter program. Please see the individual
patch for details.

Martin KaFai Lau (9):
bpf: Remove prog->active check for bpf_lsm and bpf_iter
bpf: Append _recur naming to the bpf_task_storage helper proto
bpf: Refactor the core bpf_task_storage_get logic into a new function
bpf: Avoid taking spinlock in bpf_task_storage_get if potential
deadlock is detected
bpf: Add new bpf_task_storage_get proto with no deadlock detection
bpf: bpf_task_storage_delete_recur does lookup first before the
deadlock check
bpf: Add new bpf_task_storage_delete proto with no deadlock detection
selftests/bpf: Ensure no task storage failure for bpf_lsm.s prog due
to deadlock detection
selftests/bpf: Tracing prog can still do lookup under busy lock

arch/arm64/net/bpf_jit_comp.c | 9 +-
arch/x86/net/bpf_jit_comp.c | 19 +--
include/linux/bpf.h | 26 ++--
include/linux/bpf_verifier.h | 15 +-
kernel/bpf/bpf_local_storage.c | 1 +
kernel/bpf/bpf_task_storage.c | 119 +++++++++++---
kernel/bpf/syscall.c | 5 +-
kernel/bpf/trampoline.c | 80 ++++++++--
kernel/trace/bpf_trace.c | 5 +
.../bpf/prog_tests/task_local_storage.c | 146 +++++++++++++++++-
.../selftests/bpf/progs/task_ls_recursion.c | 43 +++++-
.../bpf/progs/task_storage_nodeadlock.c | 47 ++++++
12 files changed, 431 insertions(+), 84 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/task_storage_nodeadlock.c

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2.30.2