bpf: fix percpu map update indexing with sparse CPU IDs - #13274
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Per-CPU array, hash, and cgroup storage map updates without BPF_F_CPU or BPF_F_ALL_CPUS use a value buffer whose per-CPU slots are packed in possible-CPU order. The buffer is sized as: round_up(value_size, 8) * num_possible_cpus() The update paths iterate over possible CPUs, but use the logical CPU ID to calculate the source offset: value + size * cpu This only works when possible CPU IDs are contiguous starting at zero. For example, with a possible CPU mask of 0,2-3, the buffer contains three slots corresponding to CPUs 0, 2, and 3. CPU2 is therefore expected to use slot 1 and CPU3 slot 2. Instead, the current code uses slots 2 and 3 respectively, causing incorrect per-CPU values and an out-of-bounds read from the update buffer for CPU3. The corresponding lookup paths already use a dense offset while iterating over possible CPUs. Do the same for the array, hash, and cgroup storage update paths, advancing the source offset once for each possible CPU. BPF_F_ALL_CPUS continues to use the same value for every CPU. Fixes: 8eb76cb ("bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_array maps") Fixes: c693616 ("bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_hash and lru_percpu_hash maps") Fixes: 47c79f0 ("bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_cgroup_storage maps") Acked-by: Leon Hwang <leon.hwang@linux.dev> Signed-off-by: Hui Su <sh_def@163.com>
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Pull request for series with
subject: bpf: fix percpu map update indexing with sparse CPU IDs
version: 2
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145562