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Message-ID: <202512080556.BbmGuwU4-lkp@intel.com>
Date: Mon, 8 Dec 2025 05:43:54 +0800
From: kernel test robot <lkp@...el.com>
To: Benjamin Berg <benjamin@...solutions.net>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
Johannes Berg <johannes.berg@...el.com>
Subject: arch/um/kernel/skas/stub_exe.c:180:23-24: WARNING: Use ARRAY_SIZE
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 67a454e6b1c604555c04501c77b7fedc5d98a779
commit: 406d17c6c370a33cfb54067d9e205305293d4604 um: Implement kernel side of SECCOMP based process handling
date: 6 months ago
config: um-randconfig-r064-20251207 (https://download.01.org/0day-ci/archive/20251208/202512080556.BbmGuwU4-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project a805147ac1ba123916de182babb0831fbb148756)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512080556.BbmGuwU4-lkp@intel.com/
cocci warnings: (new ones prefixed by >>)
>> arch/um/kernel/skas/stub_exe.c:180:23-24: WARNING: Use ARRAY_SIZE
vim +180 arch/um/kernel/skas/stub_exe.c
11
12 noinline static void real_init(void)
13 {
14 struct stub_init_data init_data;
15 unsigned long res;
16 struct {
17 void *ss_sp;
18 int ss_flags;
19 size_t ss_size;
20 } stack = {
21 .ss_size = STUB_DATA_PAGES * UM_KERN_PAGE_SIZE,
22 };
23 struct {
24 void *sa_handler_;
25 unsigned long sa_flags;
26 void *sa_restorer;
27 unsigned long long sa_mask;
28 } sa = {
29 /* Need to set SA_RESTORER (but the handler never returns) */
30 .sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO | 0x04000000,
31 };
32
33 /* set a nice name */
34 stub_syscall2(__NR_prctl, PR_SET_NAME, (unsigned long)"uml-userspace");
35
36 /* Make sure this process dies if the kernel dies */
37 stub_syscall2(__NR_prctl, PR_SET_PDEATHSIG, SIGKILL);
38
39 /* Needed in SECCOMP mode (and safe to do anyway) */
40 stub_syscall5(__NR_prctl, PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
41
42 /* read information from STDIN and close it */
43 res = stub_syscall3(__NR_read, 0,
44 (unsigned long)&init_data, sizeof(init_data));
45 if (res != sizeof(init_data))
46 stub_syscall1(__NR_exit, 10);
47
48 stub_syscall1(__NR_close, 0);
49
50 /* map stub code + data */
51 res = stub_syscall6(STUB_MMAP_NR,
52 init_data.stub_start, UM_KERN_PAGE_SIZE,
53 PROT_READ | PROT_EXEC, MAP_FIXED | MAP_SHARED,
54 init_data.stub_code_fd, init_data.stub_code_offset);
55 if (res != init_data.stub_start)
56 stub_syscall1(__NR_exit, 11);
57
58 res = stub_syscall6(STUB_MMAP_NR,
59 init_data.stub_start + UM_KERN_PAGE_SIZE,
60 STUB_DATA_PAGES * UM_KERN_PAGE_SIZE,
61 PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED,
62 init_data.stub_data_fd, init_data.stub_data_offset);
63 if (res != init_data.stub_start + UM_KERN_PAGE_SIZE)
64 stub_syscall1(__NR_exit, 12);
65
66 /* setup signal stack inside stub data */
67 stack.ss_sp = (void *)init_data.stub_start + UM_KERN_PAGE_SIZE;
68 stub_syscall2(__NR_sigaltstack, (unsigned long)&stack, 0);
69
70 /* register signal handlers */
71 sa.sa_handler_ = (void *) init_data.signal_handler;
72 sa.sa_restorer = (void *) init_data.signal_restorer;
73 if (!init_data.seccomp) {
74 /* In ptrace mode, the SIGSEGV handler never returns */
75 sa.sa_mask = 0;
76
77 res = stub_syscall4(__NR_rt_sigaction, SIGSEGV,
78 (unsigned long)&sa, 0, sizeof(sa.sa_mask));
79 if (res != 0)
80 stub_syscall1(__NR_exit, 13);
81 } else {
82 /* SECCOMP mode uses rt_sigreturn, need to mask all signals */
83 sa.sa_mask = ~0ULL;
84
85 res = stub_syscall4(__NR_rt_sigaction, SIGSEGV,
86 (unsigned long)&sa, 0, sizeof(sa.sa_mask));
87 if (res != 0)
88 stub_syscall1(__NR_exit, 14);
89
90 res = stub_syscall4(__NR_rt_sigaction, SIGSYS,
91 (unsigned long)&sa, 0, sizeof(sa.sa_mask));
92 if (res != 0)
93 stub_syscall1(__NR_exit, 15);
94
95 res = stub_syscall4(__NR_rt_sigaction, SIGALRM,
96 (unsigned long)&sa, 0, sizeof(sa.sa_mask));
97 if (res != 0)
98 stub_syscall1(__NR_exit, 16);
99
100 res = stub_syscall4(__NR_rt_sigaction, SIGTRAP,
101 (unsigned long)&sa, 0, sizeof(sa.sa_mask));
102 if (res != 0)
103 stub_syscall1(__NR_exit, 17);
104
105 res = stub_syscall4(__NR_rt_sigaction, SIGILL,
106 (unsigned long)&sa, 0, sizeof(sa.sa_mask));
107 if (res != 0)
108 stub_syscall1(__NR_exit, 18);
109
110 res = stub_syscall4(__NR_rt_sigaction, SIGFPE,
111 (unsigned long)&sa, 0, sizeof(sa.sa_mask));
112 if (res != 0)
113 stub_syscall1(__NR_exit, 19);
114 }
115
116 /*
117 * If in seccomp mode, install the SECCOMP filter and trigger a syscall.
118 * Otherwise set PTRACE_TRACEME and do a SIGSTOP.
119 */
120 if (init_data.seccomp) {
121 struct sock_filter filter[] = {
122 #if __BITS_PER_LONG > 32
123 /* [0] Load upper 32bit of instruction pointer from seccomp_data */
124 BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
125 (offsetof(struct seccomp_data, instruction_pointer) + 4)),
126
127 /* [1] Jump forward 3 instructions if the upper address is not identical */
128 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, (init_data.stub_start) >> 32, 0, 3),
129 #endif
130 /* [2] Load lower 32bit of instruction pointer from seccomp_data */
131 BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
132 (offsetof(struct seccomp_data, instruction_pointer))),
133
134 /* [3] Mask out lower bits */
135 BPF_STMT(BPF_ALU | BPF_AND | BPF_K, 0xfffff000),
136
137 /* [4] Jump to [6] if the lower bits are not on the expected page */
138 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, (init_data.stub_start) & 0xfffff000, 1, 0),
139
140 /* [5] Trap call, allow */
141 BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_TRAP),
142
143 /* [6,7] Check architecture */
144 BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
145 offsetof(struct seccomp_data, arch)),
146 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K,
147 UM_SECCOMP_ARCH_NATIVE, 1, 0),
148
149 /* [8] Kill (for architecture check) */
150 BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_KILL_PROCESS),
151
152 /* [9] Load syscall number */
153 BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
154 offsetof(struct seccomp_data, nr)),
155
156 /* [10-14] Check against permitted syscalls */
157 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_futex,
158 5, 0),
159 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, STUB_MMAP_NR,
160 4, 0),
161 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_munmap,
162 3, 0),
163 #ifdef __i386__
164 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_set_thread_area,
165 2, 0),
166 #else
167 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_arch_prctl,
168 2, 0),
169 #endif
170 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_rt_sigreturn,
171 1, 0),
172
173 /* [15] Not one of the permitted syscalls */
174 BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_KILL_PROCESS),
175
176 /* [16] Permitted call for the stub */
177 BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
178 };
179 struct sock_fprog prog = {
> 180 .len = sizeof(filter) / sizeof(filter[0]),
181 .filter = filter,
182 };
183
184 if (stub_syscall3(__NR_seccomp, SECCOMP_SET_MODE_FILTER,
185 SECCOMP_FILTER_FLAG_TSYNC,
186 (unsigned long)&prog) != 0)
187 stub_syscall1(__NR_exit, 20);
188
189 /* Fall through, the exit syscall will cause SIGSYS */
190 } else {
191 stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0);
192
193 stub_syscall2(__NR_kill, stub_syscall0(__NR_getpid), SIGSTOP);
194 }
195
196 stub_syscall1(__NR_exit, 30);
197
198 __builtin_unreachable();
199 }
200
--
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