Fix acting[] array out-of-bounds access in radostrace#87
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pponnuvel merged 2 commits intotaodd:mainfrom Mar 31, 2026
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Fix acting[] array out-of-bounds access in radostrace#87pponnuvel merged 2 commits intotaodd:mainfrom
pponnuvel merged 2 commits intotaodd:mainfrom
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Overall looks good to me, some minor suggestions
The acting[] array in client_op_v was defined with a fixed size of 6, but the loop iterating over it used a hardcoded bound of 8, causing out-of-bounds reads. Beyond fixing the mismatch, the array was too small for real Ceph deployments. Ceph caps the number of OSDs per PG at CEPH_PG_MAX_SIZE (16), defined in src/include/rados.h. This applies to both replicated pools (max size=10 enforced by OSDMonitor) and erasure-coded pools (k+m bounded by CEPH_PG_MAX_SIZE). The Linux kernel client uses the same constant to size its acting set arrays (struct ceph_osds in osdmap.h). Changes: - Define MAX_ACTING=16 macro in bpf_ceph_types.h, matching CEPH_PG_MAX_SIZE from Ceph's rados.h - Use MAX_ACTING for acting[] array size and all loop bounds - Move initialize_value() stack allocation to a .bss global (zero_val) to avoid BPF 512-byte stack limit, since client_op_v with acting[16] is ~434 bytes Signed-off-by: Seyeong Kim <seyeong.kim@canonical.com>
bpf_ringbuf_reserve() was using sizeof(struct op_v) but the code copies a struct client_op_v into the reserved buffer. With the acting[] array expansion this became a detectable OOB write caught by the BPF verifier. Signed-off-by: Seyeong Kim <seyeong.kim@canonical.com>
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acting[] was originally declared as acting[8] in commit a224791, with matching loop bounds of i < 8. Later, commit ada1407 reduced the array to acting[6] to make room for cls_ops[3], but forgot to update the loop bounds in radostrace.cc and radostrace.bpf.c, causing OOB access.