Fixes for stack with allow_ptr_leaks #8133
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Upstream branch: c8d02b5 |
Inside mark_stack_slot_misc, we should not upgrade STACK_INVALID to STACK_MISC when allow_ptr_leaks is false, since invalid contents shouldn't be read unless the program has the relevant capabilities. The relaxation only makes sense when env->allow_ptr_leaks is true. Currently, the condition is inverted (i.e. checking for true instead of false), simply invert it to restore correct behavior. Update error strings of selftests relying on current behavior's verifier output. Fixes: eaf18fe ("bpf: preserve STACK_ZERO slots on partial reg spills") Reported-by: Tao Lyu <[email protected]> Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
When CAP_PERFMON and CAP_SYS_ADMIN (allow_ptr_leaks) are disabled, the verifier aims to reject partial overwrite on an 8-byte stack slot that contains a spilled pointer. However, in such a scenario, it rejects all partial stack overwrites as long as the targeted stack slot is a spilled register, because it does not check if the stack slot is a spilled pointer. Incomplete checks will result in the rejection of valid programs, which spill narrower scalar values onto scalar slots, as shown below. 0: R1=ctx() R10=fp0 ; asm volatile ( @ repro.bpf.c:679 0: (7a) *(u64 *)(r10 -8) = 1 ; R10=fp0 fp-8_w=1 1: (62) *(u32 *)(r10 -8) = 1 attempt to corrupt spilled pointer on stack processed 2 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0. Fix this by expanding the check to not consider spilled scalar registers when rejecting the write into the stack. Previous discussion on this patch is at link [0]. [0]: https://lore.kernel.org/bpf/[email protected] Fixes: ab125ed ("bpf: fix check for attempt to corrupt spilled pointer") Signed-off-by: Tao Lyu <[email protected]> Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
Ensure that when CAP_PERFMON is dropped, and the verifier sees allow_ptr_leaks as false, we are not permitted to read from a STACK_INVALID slot. Without the fix, the test will report unexpected success in loading. Since we need to control the capabilities when loading this test to only retain CAP_BPF, refactor support added to do the same for test_verifier_mtu and reuse it for this selftest to avoid copy-paste. Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
Add a test case to verify that without CAP_PERFMON, the test now succeeds instead of failing due to a verification error. Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
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Upstream branch: c8d02b5 |
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Pull request for series with
subject: Fixes for stack with allow_ptr_leaks
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=912895