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selftests/bpf: Test RCU iterator state pruning

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Add a path where RCU protection reaches zero and then starts again.
The iterator is untrusted after this gap and must be rejected.

Signed-off-by: Ning Ding <dingning04@gmail.com>
Link: https://patch.msgid.link/20260811035955.132989-3-dingning04@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
This commit is contained in:
Ning Ding
2026-08-10 20:59:55 -07:00
committed by Eduard Zingerman
parent 83608e303b
commit 81f209d5f7
1 changed files with 46 additions and 0 deletions
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46
tools/testing/selftests/bpf/progs/iters_task_failure.c
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@@ -61,6 +61,52 @@ int BPF_PROG(iter_tasks_lock_and_unlock)
return 0;
}
SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
__failure __msg("expected an RCU CS when using bpf_iter_task_next")
__flag(BPF_F_TEST_STATE_FREQ)
int BPF_PROG(iter_tasks_rcu_state_pruning)
{
struct bpf_iter_task it;
asm volatile (
"call %[bpf_rcu_read_lock];"
"r1 = %[it];"
"r2 = 0;"
"r3 = 0;" /* BPF_TASK_ITER_ALL_PROCS */
"call %[bpf_iter_task_new];"
"call %[bpf_get_prandom_u32];"
"if w0 == 0 goto unprotected_%=;"
/* Keep the outer RCU lock active on the straight-line path. */
"call %[bpf_rcu_read_lock];"
"call %[bpf_rcu_read_unlock];"
"goto merge_%=;"
"unprotected_%=:"
/* Create an unprotected gap on the taken path. */
"call %[bpf_rcu_read_unlock];"
"call %[bpf_rcu_read_lock];"
"merge_%=: r1 = %[it];"
"call %[bpf_iter_task_next];"
"r1 = %[it];"
"call %[bpf_iter_task_destroy];"
"call %[bpf_rcu_read_unlock];"
:
: __imm_ptr(it),
__imm(bpf_get_prandom_u32),
__imm(bpf_iter_task_new),
__imm(bpf_iter_task_next),
__imm(bpf_iter_task_destroy),
__imm(bpf_rcu_read_lock),
__imm(bpf_rcu_read_unlock)
: __clobber_common
);
return 0;
}
SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
__failure __msg("expected an RCU CS when using bpf_iter_css_next")
int BPF_PROG(iter_css_lock_and_unlock)