arch/x86/kernel/signal_compat.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/compat.h>
   3 #include <linux/uaccess.h>
   4 #include <linux/ptrace.h>
   5
   6 /*
   7  * The compat_siginfo_t structure and handing code is very easy
   8  * to break in several ways.  It must always be updated when new
   9  * updates are made to the main siginfo_t, and
  10  * copy_siginfo_to_user32() must be updated when the
  11  * (arch-independent) copy_siginfo_to_user() is updated.
  12  *
  13  * It is also easy to put a new member in the compat_siginfo_t
  14  * which has implicit alignment which can move internal structure
  15  * alignment around breaking the ABI.  This can happen if you,
  16  * for instance, put a plain 64-bit value in there.
  17  */
  18 static inline void signal_compat_build_tests(void)
  19 {
  20         int _sifields_offset = offsetof(compat_siginfo_t, _sifields);
  21
  22         /*
  23          * If adding a new si_code, there is probably new data in
  24          * the siginfo.  Make sure folks bumping the si_code
  25          * limits also have to look at this code.  Make sure any
  26          * new fields are handled in copy_siginfo_to_user32()!
  27          */
  28         BUILD_BUG_ON(NSIGILL  != 11);
  29         BUILD_BUG_ON(NSIGFPE  != 15);
  30         BUILD_BUG_ON(NSIGSEGV != 7);
  31         BUILD_BUG_ON(NSIGBUS  != 5);
  32         BUILD_BUG_ON(NSIGTRAP != 5);
  33         BUILD_BUG_ON(NSIGCHLD != 6);
  34         BUILD_BUG_ON(NSIGSYS  != 1);
  35
  36         /* This is part of the ABI and can never change in size: */
  37         BUILD_BUG_ON(sizeof(compat_siginfo_t) != 128);
  38         /*
  39          * The offsets of all the (unioned) si_fields are fixed
  40          * in the ABI, of course.  Make sure none of them ever
  41          * move and are always at the beginning:
  42          */
  43         BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields) != 3 * sizeof(int));
  44 #define CHECK_CSI_OFFSET(name)    BUILD_BUG_ON(_sifields_offset != offsetof(compat_siginfo_t, _sifields.name))
  45
  46         BUILD_BUG_ON(offsetof(siginfo_t, si_signo) != 0);
  47         BUILD_BUG_ON(offsetof(siginfo_t, si_errno) != 4);
  48         BUILD_BUG_ON(offsetof(siginfo_t, si_code)  != 8);
  49
  50         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_signo) != 0);
  51         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_errno) != 4);
  52         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_code)  != 8);
  53          /*
  54          * Ensure that the size of each si_field never changes.
  55          * If it does, it is a sign that the
  56          * copy_siginfo_to_user32() code below needs to updated
  57          * along with the size in the CHECK_SI_SIZE().
  58          *
  59          * We repeat this check for both the generic and compat
  60          * siginfos.
  61          *
  62          * Note: it is OK for these to grow as long as the whole
  63          * structure stays within the padding size (checked
  64          * above).
  65          */
  66 #define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name))
  67 #define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name))
  68
  69         CHECK_CSI_OFFSET(_kill);
  70         CHECK_CSI_SIZE  (_kill, 2*sizeof(int));
  71         CHECK_SI_SIZE   (_kill, 2*sizeof(int));
  72
  73         BUILD_BUG_ON(offsetof(siginfo_t, si_pid) != 0x10);
  74         BUILD_BUG_ON(offsetof(siginfo_t, si_uid) != 0x14);
  75         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_pid) != 0xC);
  76         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_uid) != 0x10);
  77
  78         CHECK_CSI_OFFSET(_timer);
  79         CHECK_CSI_SIZE  (_timer, 3*sizeof(int));
  80         CHECK_SI_SIZE   (_timer, 6*sizeof(int));
  81
  82         BUILD_BUG_ON(offsetof(siginfo_t, si_tid)     != 0x10);
  83         BUILD_BUG_ON(offsetof(siginfo_t, si_overrun) != 0x14);
  84         BUILD_BUG_ON(offsetof(siginfo_t, si_value)   != 0x18);
  85         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_tid)     != 0x0C);
  86         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_overrun) != 0x10);
  87         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_value)   != 0x14);
  88
  89         CHECK_CSI_OFFSET(_rt);
  90         CHECK_CSI_SIZE  (_rt, 3*sizeof(int));
  91         CHECK_SI_SIZE   (_rt, 4*sizeof(int));
  92
  93         BUILD_BUG_ON(offsetof(siginfo_t, si_pid)   != 0x10);
  94         BUILD_BUG_ON(offsetof(siginfo_t, si_uid)   != 0x14);
  95         BUILD_BUG_ON(offsetof(siginfo_t, si_value) != 0x18);
  96         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_pid)   != 0x0C);
  97         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_uid)   != 0x10);
  98         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_value) != 0x14);
  99
 100         CHECK_CSI_OFFSET(_sigchld);
 101         CHECK_CSI_SIZE  (_sigchld, 5*sizeof(int));
 102         CHECK_SI_SIZE   (_sigchld, 8*sizeof(int));
 103
 104         BUILD_BUG_ON(offsetof(siginfo_t, si_pid)    != 0x10);
 105         BUILD_BUG_ON(offsetof(siginfo_t, si_uid)    != 0x14);
 106         BUILD_BUG_ON(offsetof(siginfo_t, si_status) != 0x18);
 107         BUILD_BUG_ON(offsetof(siginfo_t, si_utime)  != 0x20);
 108         BUILD_BUG_ON(offsetof(siginfo_t, si_stime)  != 0x28);
 109         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_pid)    != 0x0C);
 110         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_uid)    != 0x10);
 111         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_status) != 0x14);
 112         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_utime)  != 0x18);
 113         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_stime)  != 0x1C);
 114
 115 #ifdef CONFIG_X86_X32_ABI
 116         CHECK_CSI_OFFSET(_sigchld_x32);
 117         CHECK_CSI_SIZE  (_sigchld_x32, 7*sizeof(int));
 118         /* no _sigchld_x32 in the generic siginfo_t */
 119         BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields._sigchld_x32._utime)  != 0x18);
 120         BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields._sigchld_x32._stime)  != 0x20);
 121 #endif
 122
 123         CHECK_CSI_OFFSET(_sigfault);
 124         CHECK_CSI_SIZE  (_sigfault, 4*sizeof(int));
 125         CHECK_SI_SIZE   (_sigfault, 8*sizeof(int));
 126
 127         BUILD_BUG_ON(offsetof(siginfo_t, si_addr) != 0x10);
 128         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_addr) != 0x0C);
 129
 130         BUILD_BUG_ON(offsetof(siginfo_t, si_addr_lsb) != 0x18);
 131         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_addr_lsb) != 0x10);
 132
 133         BUILD_BUG_ON(offsetof(siginfo_t, si_lower) != 0x20);
 134         BUILD_BUG_ON(offsetof(siginfo_t, si_upper) != 0x28);
 135         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_lower) != 0x14);
 136         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_upper) != 0x18);
 137
 138         BUILD_BUG_ON(offsetof(siginfo_t, si_pkey) != 0x20);
 139         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_pkey) != 0x14);
 140
 141         CHECK_CSI_OFFSET(_sigpoll);
 142         CHECK_CSI_SIZE  (_sigpoll, 2*sizeof(int));
 143         CHECK_SI_SIZE   (_sigpoll, 4*sizeof(int));
 144
 145         BUILD_BUG_ON(offsetof(siginfo_t, si_band)   != 0x10);
 146         BUILD_BUG_ON(offsetof(siginfo_t, si_fd)     != 0x18);
 147         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_band) != 0x0C);
 148         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_fd)   != 0x10);
 149
 150         CHECK_CSI_OFFSET(_sigsys);
 151         CHECK_CSI_SIZE  (_sigsys, 3*sizeof(int));
 152         CHECK_SI_SIZE   (_sigsys, 4*sizeof(int));
 153
 154         BUILD_BUG_ON(offsetof(siginfo_t, si_call_addr) != 0x10);
 155         BUILD_BUG_ON(offsetof(siginfo_t, si_syscall)   != 0x18);
 156         BUILD_BUG_ON(offsetof(siginfo_t, si_arch)      != 0x1C);
 157         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_call_addr) != 0x0C);
 158         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_syscall)   != 0x10);
 159         BUILD_BUG_ON(offsetof(compat_siginfo_t, si_arch)      != 0x14);
 160
 161         /* any new si_fields should be added here */
 162 }
 163
 164 void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
 165 {
 166         signal_compat_build_tests();
 167
 168         /* Don't leak in-kernel non-uapi flags to user-space */
 169         if (oact)
 170                 oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
 171
 172         if (!act)
 173                 return;
 174
 175         /* Don't let flags to be set from userspace */
 176         act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
 177
 178         if (in_ia32_syscall())
 179                 act->sa.sa_flags |= SA_IA32_ABI;
 180         if (in_x32_syscall())
 181                 act->sa.sa_flags |= SA_X32_ABI;
 182 }