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  != 13);
  30         BUILD_BUG_ON(NSIGSEGV != 4);
  31         BUILD_BUG_ON(NSIGBUS  != 5);
  32         BUILD_BUG_ON(NSIGTRAP != 4);
  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          /*
  47          * Ensure that the size of each si_field never changes.
  48          * If it does, it is a sign that the
  49          * copy_siginfo_to_user32() code below needs to updated
  50          * along with the size in the CHECK_SI_SIZE().
  51          *
  52          * We repeat this check for both the generic and compat
  53          * siginfos.
  54          *
  55          * Note: it is OK for these to grow as long as the whole
  56          * structure stays within the padding size (checked
  57          * above).
  58          */
  59 #define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name))
  60 #define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name))
  61
  62         CHECK_CSI_OFFSET(_kill);
  63         CHECK_CSI_SIZE  (_kill, 2*sizeof(int));
  64         CHECK_SI_SIZE   (_kill, 2*sizeof(int));
  65
  66         CHECK_CSI_OFFSET(_timer);
  67         CHECK_CSI_SIZE  (_timer, 3*sizeof(int));
  68         CHECK_SI_SIZE   (_timer, 6*sizeof(int));
  69
  70         CHECK_CSI_OFFSET(_rt);
  71         CHECK_CSI_SIZE  (_rt, 3*sizeof(int));
  72         CHECK_SI_SIZE   (_rt, 4*sizeof(int));
  73
  74         CHECK_CSI_OFFSET(_sigchld);
  75         CHECK_CSI_SIZE  (_sigchld, 5*sizeof(int));
  76         CHECK_SI_SIZE   (_sigchld, 8*sizeof(int));
  77
  78 #ifdef CONFIG_X86_X32_ABI
  79         CHECK_CSI_OFFSET(_sigchld_x32);
  80         CHECK_CSI_SIZE  (_sigchld_x32, 7*sizeof(int));
  81         /* no _sigchld_x32 in the generic siginfo_t */
  82 #endif
  83
  84         CHECK_CSI_OFFSET(_sigfault);
  85         CHECK_CSI_SIZE  (_sigfault, 4*sizeof(int));
  86         CHECK_SI_SIZE   (_sigfault, 8*sizeof(int));
  87
  88         CHECK_CSI_OFFSET(_sigpoll);
  89         CHECK_CSI_SIZE  (_sigpoll, 2*sizeof(int));
  90         CHECK_SI_SIZE   (_sigpoll, 4*sizeof(int));
  91
  92         CHECK_CSI_OFFSET(_sigsys);
  93         CHECK_CSI_SIZE  (_sigsys, 3*sizeof(int));
  94         CHECK_SI_SIZE   (_sigsys, 4*sizeof(int));
  95
  96         /* any new si_fields should be added here */
  97 }
  98
  99 void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
 100 {
 101         signal_compat_build_tests();
 102
 103         /* Don't leak in-kernel non-uapi flags to user-space */
 104         if (oact)
 105                 oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
 106
 107         if (!act)
 108                 return;
 109
 110         /* Don't let flags to be set from userspace */
 111         act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
 112
 113         if (in_ia32_syscall())
 114                 act->sa.sa_flags |= SA_IA32_ABI;
 115         if (in_x32_syscall())
 116                 act->sa.sa_flags |= SA_X32_ABI;
 117 }