In the Linux kernel, the following vulnerability has been resolved:bpf: Mark bpf prog stack with kmsan_unposion_memory in interpreter modesyzbot reported uninit memory usages during map_{lookup,delete}_elem.==========BUG: KMSAN: uninit-value in __dev_map_lookup_elem kernel/bpf/devmap.c:441 inline]BUG: KMSAN: uninit-value in dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796__dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796____bpf_map_lookup_elem kernel/bpf/helpers.c:42 [inline]bpf_map_lookup_elem+0x5c/0x80 kernel/bpf/helpers.c:38___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997__bpf_prog_run256+0xb5/0xe0 kernel/bpf/core.c:2237==========The reproducer should be in the interpreter mode.The C reproducer is trying to run the following bpf prog: 0: (18) r0 = 0x0 2: (18) r1 = map[id:49] 4: (b7) r8 = 16777216 5: (7b) *(u64 *)(r10 -8) = r8 6: (bf) r2 = r10 7: (07) r2 += -229 ^^^^^^^^^^ 8: (b7) r3 = 8 9: (b7) r4 = 0 10: (85) call dev_map_lookup_elem#1543472 11: (95) exitIt is due to the "void *key" (r2) passed to the helper. bpf allows uninitstack memory access for bpf prog with the right privileges. This patchuses kmsan_unpoison_memory() to mark the stack as initialized.This should address different syzbot reports on the uninit "void *key"argument during map_{lookup,delete}_elem.
CREATE(Triage):(User=admin) [CVE-2024-42063 (https://nvd.nist.gov/vuln/detail/CVE-2024-42063)
