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ed54bf564a
BPF_F_CPU stores the target CPU ID in the upper 32 bits of the map
operation flags. bpf_map_check_op_flags() currently compares that ID
with num_possible_cpus(), which is the number of possible CPUs rather
than a bound on CPU IDs.
On an arm64 QEMU guest with a CPU device-tree hole, the possible CPU
mask was 0,2-3. A userspace program using raw bpf() syscalls creates
a BPF_MAP_TYPE_PERCPU_ARRAY and performs update and lookup operations
for each CPU by setting BPF_F_CPU and the CPU ID in the flags.
With the old check, CPU 1 is incorrectly accepted while valid CPU 3 is
rejected with -ERANGE. The CPU 1 update then reaches the per-CPU map
access path and triggers:
Unable to handle kernel paging request at virtual address ...
pc : __pi_memcpy_generic+0x5c/0x22c
lr : bpf_percpu_array_update+0x2dc/0x2e8
Call trace:
__pi_memcpy_generic
bpf_map_update_value
map_update_elem
__sys_bpf
Check the CPU ID against nr_cpu_ids and cpu_possible() instead. This
rejects CPU IDs outside the valid range and CPUs absent from the
possible mask, while allowing valid sparse CPU IDs.
Fixes:
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|---|---|---|
| .. | ||
| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| cxl | ||
| drm | ||
| dt-bindings | ||
| hyperv | ||
| keys | ||
| kunit | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rv | ||
| scsi | ||
| soc | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| ufs | ||
| vdso | ||
| video | ||
| xen | ||
| Kbuild | ||