arch/x86/kernel/signal_compat.c

   1 #include <linux/compat.h>
   2 #include <linux/uaccess.h>
   3 #include <linux/ptrace.h>
   4
   5 /*
   6  * The compat_siginfo_t structure and handing code is very easy
   7  * to break in several ways.  It must always be updated when new
   8  * updates are made to the main siginfo_t, and
   9  * copy_siginfo_to_user32() must be updated when the
  10  * (arch-independent) copy_siginfo_to_user() is updated.
  11  *
  12  * It is also easy to put a new member in the compat_siginfo_t
  13  * which has implicit alignment which can move internal structure
  14  * alignment around breaking the ABI.  This can happen if you,
  15  * for instance, put a plain 64-bit value in there.
  16  */
  17 static inline void signal_compat_build_tests(void)
  18 {
  19         int _sifields_offset = offsetof(compat_siginfo_t, _sifields);
  20
  21         /*
  22          * If adding a new si_code, there is probably new data in
  23          * the siginfo.  Make sure folks bumping the si_code
  24          * limits also have to look at this code.  Make sure any
  25          * new fields are handled in copy_siginfo_to_user32()!
  26          */
  27         BUILD_BUG_ON(NSIGILL  != 8);
  28         BUILD_BUG_ON(NSIGFPE  != 8);
  29         BUILD_BUG_ON(NSIGSEGV != 4);
  30         BUILD_BUG_ON(NSIGBUS  != 5);
  31         BUILD_BUG_ON(NSIGTRAP != 4);
  32         BUILD_BUG_ON(NSIGCHLD != 6);
  33         BUILD_BUG_ON(NSIGSYS  != 1);
  34
  35         /* This is part of the ABI and can never change in size: */
  36         BUILD_BUG_ON(sizeof(compat_siginfo_t) != 128);
  37         /*
  38          * The offsets of all the (unioned) si_fields are fixed
  39          * in the ABI, of course.  Make sure none of them ever
  40          * move and are always at the beginning:
  41          */
  42         BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields) != 3 * sizeof(int));
  43 #define CHECK_CSI_OFFSET(name)    BUILD_BUG_ON(_sifields_offset != offsetof(compat_siginfo_t, _sifields.name))
  44
  45          /*
  46          * Ensure that the size of each si_field never changes.
  47          * If it does, it is a sign that the
  48          * copy_siginfo_to_user32() code below needs to updated
  49          * along with the size in the CHECK_SI_SIZE().
  50          *
  51          * We repeat this check for both the generic and compat
  52          * siginfos.
  53          *
  54          * Note: it is OK for these to grow as long as the whole
  55          * structure stays within the padding size (checked
  56          * above).
  57          */
  58 #define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name))
  59 #define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name))
  60
  61         CHECK_CSI_OFFSET(_kill);
  62         CHECK_CSI_SIZE  (_kill, 2*sizeof(int));
  63         CHECK_SI_SIZE   (_kill, 2*sizeof(int));
  64
  65         CHECK_CSI_OFFSET(_timer);
  66         CHECK_CSI_SIZE  (_timer, 5*sizeof(int));
  67         CHECK_SI_SIZE   (_timer, 6*sizeof(int));
  68
  69         CHECK_CSI_OFFSET(_rt);
  70         CHECK_CSI_SIZE  (_rt, 3*sizeof(int));
  71         CHECK_SI_SIZE   (_rt, 4*sizeof(int));
  72
  73         CHECK_CSI_OFFSET(_sigchld);
  74         CHECK_CSI_SIZE  (_sigchld, 5*sizeof(int));
  75         CHECK_SI_SIZE   (_sigchld, 8*sizeof(int));
  76
  77         CHECK_CSI_OFFSET(_sigchld_x32);
  78         CHECK_CSI_SIZE  (_sigchld_x32, 7*sizeof(int));
  79         /* no _sigchld_x32 in the generic siginfo_t */
  80
  81         CHECK_CSI_OFFSET(_sigfault);
  82         CHECK_CSI_SIZE  (_sigfault, 4*sizeof(int));
  83         CHECK_SI_SIZE   (_sigfault, 8*sizeof(int));
  84
  85         CHECK_CSI_OFFSET(_sigpoll);
  86         CHECK_CSI_SIZE  (_sigpoll, 2*sizeof(int));
  87         CHECK_SI_SIZE   (_sigpoll, 4*sizeof(int));
  88
  89         CHECK_CSI_OFFSET(_sigsys);
  90         CHECK_CSI_SIZE  (_sigsys, 3*sizeof(int));
  91         CHECK_SI_SIZE   (_sigsys, 4*sizeof(int));
  92
  93         /* any new si_fields should be added here */
  94 }
  95
  96 void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
  97 {
  98         /* Don't leak in-kernel non-uapi flags to user-space */
  99         if (oact)
 100                 oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
 101
 102         if (!act)
 103                 return;
 104
 105         /* Don't let flags to be set from userspace */
 106         act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
 107
 108         if (in_ia32_syscall())
 109                 act->sa.sa_flags |= SA_IA32_ABI;
 110         if (in_x32_syscall())
 111                 act->sa.sa_flags |= SA_X32_ABI;
 112 }
 113
 114 int __copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from,
 115                 bool x32_ABI)
 116 {
 117         int err = 0;
 118
 119         signal_compat_build_tests();
 120
 121         if (!access_ok(VERIFY_WRITE, to, sizeof(compat_siginfo_t)))
 122                 return -EFAULT;
 123
 124         put_user_try {
 125                 /* If you change siginfo_t structure, please make sure that
 126                    this code is fixed accordingly.
 127                    It should never copy any pad contained in the structure
 128                    to avoid security leaks, but must copy the generic
 129                    3 ints plus the relevant union member.  */
 130                 put_user_ex(from->si_signo, &to->si_signo);
 131                 put_user_ex(from->si_errno, &to->si_errno);
 132                 put_user_ex((short)from->si_code, &to->si_code);
 133
 134                 if (from->si_code < 0) {
 135                         put_user_ex(from->si_pid, &to->si_pid);
 136                         put_user_ex(from->si_uid, &to->si_uid);
 137                         put_user_ex(ptr_to_compat(from->si_ptr), &to->si_ptr);
 138                 } else {
 139                         /*
 140                          * First 32bits of unions are always present:
 141                          * si_pid === si_band === si_tid === si_addr(LS half)
 142                          */
 143                         put_user_ex(from->_sifields._pad[0],
 144                                           &to->_sifields._pad[0]);
 145                         switch (from->si_code >> 16) {
 146                         case __SI_FAULT >> 16:
 147                                 if (from->si_signo == SIGBUS &&
 148                                     (from->si_code == BUS_MCEERR_AR ||
 149                                      from->si_code == BUS_MCEERR_AO))
 150                                         put_user_ex(from->si_addr_lsb, &to->si_addr_lsb);
 151
 152                                 if (from->si_signo == SIGSEGV) {
 153                                         if (from->si_code == SEGV_BNDERR) {
 154                                                 compat_uptr_t lower = (unsigned long)from->si_lower;
 155                                                 compat_uptr_t upper = (unsigned long)from->si_upper;
 156                                                 put_user_ex(lower, &to->si_lower);
 157                                                 put_user_ex(upper, &to->si_upper);
 158                                         }
 159                                         if (from->si_code == SEGV_PKUERR)
 160                                                 put_user_ex(from->si_pkey, &to->si_pkey);
 161                                 }
 162                                 break;
 163                         case __SI_SYS >> 16:
 164                                 put_user_ex(from->si_syscall, &to->si_syscall);
 165                                 put_user_ex(from->si_arch, &to->si_arch);
 166                                 break;
 167                         case __SI_CHLD >> 16:
 168                                 if (!x32_ABI) {
 169                                         put_user_ex(from->si_utime, &to->si_utime);
 170                                         put_user_ex(from->si_stime, &to->si_stime);
 171                                 } else {
 172                                         put_user_ex(from->si_utime, &to->_sifields._sigchld_x32._utime);
 173                                         put_user_ex(from->si_stime, &to->_sifields._sigchld_x32._stime);
 174                                 }
 175                                 put_user_ex(from->si_status, &to->si_status);
 176                                 /* FALL THROUGH */
 177                         default:
 178                         case __SI_KILL >> 16:
 179                                 put_user_ex(from->si_uid, &to->si_uid);
 180                                 break;
 181                         case __SI_POLL >> 16:
 182                                 put_user_ex(from->si_fd, &to->si_fd);
 183                                 break;
 184                         case __SI_TIMER >> 16:
 185                                 put_user_ex(from->si_overrun, &to->si_overrun);
 186                                 put_user_ex(ptr_to_compat(from->si_ptr),
 187                                             &to->si_ptr);
 188                                 break;
 189                                  /* This is not generated by the kernel as of now.  */
 190                         case __SI_RT >> 16:
 191                         case __SI_MESGQ >> 16:
 192                                 put_user_ex(from->si_uid, &to->si_uid);
 193                                 put_user_ex(from->si_int, &to->si_int);
 194                                 break;
 195                         }
 196                 }
 197         } put_user_catch(err);
 198
 199         return err;
 200 }
 201
 202 /* from syscall's path, where we know the ABI */
 203 int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
 204 {
 205         return __copy_siginfo_to_user32(to, from, in_x32_syscall());
 206 }
 207
 208 int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
 209 {
 210         int err = 0;
 211         u32 ptr32;
 212
 213         if (!access_ok(VERIFY_READ, from, sizeof(compat_siginfo_t)))
 214                 return -EFAULT;
 215
 216         get_user_try {
 217                 get_user_ex(to->si_signo, &from->si_signo);
 218                 get_user_ex(to->si_errno, &from->si_errno);
 219                 get_user_ex(to->si_code, &from->si_code);
 220
 221                 get_user_ex(to->si_pid, &from->si_pid);
 222                 get_user_ex(to->si_uid, &from->si_uid);
 223                 get_user_ex(ptr32, &from->si_ptr);
 224                 to->si_ptr = compat_ptr(ptr32);
 225         } get_user_catch(err);
 226
 227         return err;
 228 }