Fix resource leak checks for tail calls #4605
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There are three situations when a program logically exits and transfers control to the kernel or another program: bpf_throw, BPF_EXIT, and tail calls. The former two check for any lingering locks and references, but tail calls currently do not. Expand the checks to check for spin locks, RCU read sections and preempt disabled sections. Spin locks are indirectly preventing tail calls as function calls are disallowed, but the checks for preemption and RCU are more relaxed, hence ensure tail calls are prevented in their presence. Fixes: 9bb00b2 ("bpf: Add kfunc bpf_rcu_read_lock/unlock()") Fixes: fc7566a ("bpf: Introduce bpf_preempt_[disable,enable] kfuncs") Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
There are similar checks for covering locks, references, RCU read sections and preempt_disable sections in 3 places in the verifer, i.e. for tail calls, bpf_ld_[abs, ind], and exit path (for BPF_EXIT and bpf_throw). Unify all of these into a common check_resource_leak function to avoid code duplication. Also update the error strings in selftests to the new ones in the same change to ensure clean bisection. Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
Add failure tests to ensure bugs don't slip through for tail calls and lingering locks, RCU sections, preemption disabled sections, and references prevent tail calls. Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
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Upstream branch: 77017b9 |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=905820 irrelevant now. Closing PR. |
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Pull request for series with
subject: Fix resource leak checks for tail calls
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=905820