linux/arch/x86/kernel/signal_compat.c
Dmitry Safonov ed1e7db33c x86/signal: Remove bogus user_64bit_mode() check from sigaction_compat_abi()
The recent introduction of SA_X32/IA32 sa_flags added a check for
user_64bit_mode() into sigaction_compat_abi(). user_64bit_mode() is true
for native 64-bit processes and x32 processes.

Due to that the function returns w/o setting the SA_X32_ABI flag for X32
processes. In consequence the kernel attempts to deliver the signal to the
X32 process in native 64-bit mode causing the process to segfault.

Remove the check, so the actual check for X32 mode which sets the ABI flag
can be reached. There is no side effect for native 64-bit mode.

[ tglx: Rewrote changelog ]

Fixes: 6846351052 ("x86/signal: Add SA_{X32,IA32}_ABI sa_flags")
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Adam Borowski <kilobyte@angband.pl>
Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: linux-mm@kvack.org
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Link: http://lkml.kernel.org/r/CAJwJo6Z8ZWPqNfT6t-i8GW1MKxQrKDUagQqnZ%2B0%2B697%3DMyVeGg@mail.gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-10-20 13:05:15 +02:00

229 lines
7.0 KiB
C

#include <linux/compat.h>
#include <linux/uaccess.h>
#include <linux/ptrace.h>
/*
* The compat_siginfo_t structure and handing code is very easy
* to break in several ways. It must always be updated when new
* updates are made to the main siginfo_t, and
* copy_siginfo_to_user32() must be updated when the
* (arch-independent) copy_siginfo_to_user() is updated.
*
* It is also easy to put a new member in the compat_siginfo_t
* which has implicit alignment which can move internal structure
* alignment around breaking the ABI. This can happen if you,
* for instance, put a plain 64-bit value in there.
*/
static inline void signal_compat_build_tests(void)
{
int _sifields_offset = offsetof(compat_siginfo_t, _sifields);
/*
* If adding a new si_code, there is probably new data in
* the siginfo. Make sure folks bumping the si_code
* limits also have to look at this code. Make sure any
* new fields are handled in copy_siginfo_to_user32()!
*/
BUILD_BUG_ON(NSIGILL != 8);
BUILD_BUG_ON(NSIGFPE != 8);
BUILD_BUG_ON(NSIGSEGV != 4);
BUILD_BUG_ON(NSIGBUS != 5);
BUILD_BUG_ON(NSIGTRAP != 4);
BUILD_BUG_ON(NSIGCHLD != 6);
BUILD_BUG_ON(NSIGSYS != 1);
/* This is part of the ABI and can never change in size: */
BUILD_BUG_ON(sizeof(compat_siginfo_t) != 128);
/*
* The offsets of all the (unioned) si_fields are fixed
* in the ABI, of course. Make sure none of them ever
* move and are always at the beginning:
*/
BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields) != 3 * sizeof(int));
#define CHECK_CSI_OFFSET(name) BUILD_BUG_ON(_sifields_offset != offsetof(compat_siginfo_t, _sifields.name))
/*
* Ensure that the size of each si_field never changes.
* If it does, it is a sign that the
* copy_siginfo_to_user32() code below needs to updated
* along with the size in the CHECK_SI_SIZE().
*
* We repeat this check for both the generic and compat
* siginfos.
*
* Note: it is OK for these to grow as long as the whole
* structure stays within the padding size (checked
* above).
*/
#define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name))
#define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name))
CHECK_CSI_OFFSET(_kill);
CHECK_CSI_SIZE (_kill, 2*sizeof(int));
CHECK_SI_SIZE (_kill, 2*sizeof(int));
CHECK_CSI_OFFSET(_timer);
CHECK_CSI_SIZE (_timer, 5*sizeof(int));
CHECK_SI_SIZE (_timer, 6*sizeof(int));
CHECK_CSI_OFFSET(_rt);
CHECK_CSI_SIZE (_rt, 3*sizeof(int));
CHECK_SI_SIZE (_rt, 4*sizeof(int));
CHECK_CSI_OFFSET(_sigchld);
CHECK_CSI_SIZE (_sigchld, 5*sizeof(int));
CHECK_SI_SIZE (_sigchld, 8*sizeof(int));
CHECK_CSI_OFFSET(_sigchld_x32);
CHECK_CSI_SIZE (_sigchld_x32, 7*sizeof(int));
/* no _sigchld_x32 in the generic siginfo_t */
CHECK_CSI_OFFSET(_sigfault);
CHECK_CSI_SIZE (_sigfault, 4*sizeof(int));
CHECK_SI_SIZE (_sigfault, 8*sizeof(int));
CHECK_CSI_OFFSET(_sigpoll);
CHECK_CSI_SIZE (_sigpoll, 2*sizeof(int));
CHECK_SI_SIZE (_sigpoll, 4*sizeof(int));
CHECK_CSI_OFFSET(_sigsys);
CHECK_CSI_SIZE (_sigsys, 3*sizeof(int));
CHECK_SI_SIZE (_sigsys, 4*sizeof(int));
/* any new si_fields should be added here */
}
void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
{
/* Don't leak in-kernel non-uapi flags to user-space */
if (oact)
oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
if (!act)
return;
/* Don't let flags to be set from userspace */
act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
if (in_ia32_syscall())
act->sa.sa_flags |= SA_IA32_ABI;
if (in_x32_syscall())
act->sa.sa_flags |= SA_X32_ABI;
}
int __copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from,
bool x32_ABI)
{
int err = 0;
signal_compat_build_tests();
if (!access_ok(VERIFY_WRITE, to, sizeof(compat_siginfo_t)))
return -EFAULT;
put_user_try {
/* If you change siginfo_t structure, please make sure that
this code is fixed accordingly.
It should never copy any pad contained in the structure
to avoid security leaks, but must copy the generic
3 ints plus the relevant union member. */
put_user_ex(from->si_signo, &to->si_signo);
put_user_ex(from->si_errno, &to->si_errno);
put_user_ex((short)from->si_code, &to->si_code);
if (from->si_code < 0) {
put_user_ex(from->si_pid, &to->si_pid);
put_user_ex(from->si_uid, &to->si_uid);
put_user_ex(ptr_to_compat(from->si_ptr), &to->si_ptr);
} else {
/*
* First 32bits of unions are always present:
* si_pid === si_band === si_tid === si_addr(LS half)
*/
put_user_ex(from->_sifields._pad[0],
&to->_sifields._pad[0]);
switch (from->si_code >> 16) {
case __SI_FAULT >> 16:
if (from->si_signo == SIGBUS &&
(from->si_code == BUS_MCEERR_AR ||
from->si_code == BUS_MCEERR_AO))
put_user_ex(from->si_addr_lsb, &to->si_addr_lsb);
if (from->si_signo == SIGSEGV) {
if (from->si_code == SEGV_BNDERR) {
compat_uptr_t lower = (unsigned long)&to->si_lower;
compat_uptr_t upper = (unsigned long)&to->si_upper;
put_user_ex(lower, &to->si_lower);
put_user_ex(upper, &to->si_upper);
}
if (from->si_code == SEGV_PKUERR)
put_user_ex(from->si_pkey, &to->si_pkey);
}
break;
case __SI_SYS >> 16:
put_user_ex(from->si_syscall, &to->si_syscall);
put_user_ex(from->si_arch, &to->si_arch);
break;
case __SI_CHLD >> 16:
if (!x32_ABI) {
put_user_ex(from->si_utime, &to->si_utime);
put_user_ex(from->si_stime, &to->si_stime);
} else {
put_user_ex(from->si_utime, &to->_sifields._sigchld_x32._utime);
put_user_ex(from->si_stime, &to->_sifields._sigchld_x32._stime);
}
put_user_ex(from->si_status, &to->si_status);
/* FALL THROUGH */
default:
case __SI_KILL >> 16:
put_user_ex(from->si_uid, &to->si_uid);
break;
case __SI_POLL >> 16:
put_user_ex(from->si_fd, &to->si_fd);
break;
case __SI_TIMER >> 16:
put_user_ex(from->si_overrun, &to->si_overrun);
put_user_ex(ptr_to_compat(from->si_ptr),
&to->si_ptr);
break;
/* This is not generated by the kernel as of now. */
case __SI_RT >> 16:
case __SI_MESGQ >> 16:
put_user_ex(from->si_uid, &to->si_uid);
put_user_ex(from->si_int, &to->si_int);
break;
}
}
} put_user_catch(err);
return err;
}
/* from syscall's path, where we know the ABI */
int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
{
return __copy_siginfo_to_user32(to, from, in_x32_syscall());
}
int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
{
int err = 0;
u32 ptr32;
if (!access_ok(VERIFY_READ, from, sizeof(compat_siginfo_t)))
return -EFAULT;
get_user_try {
get_user_ex(to->si_signo, &from->si_signo);
get_user_ex(to->si_errno, &from->si_errno);
get_user_ex(to->si_code, &from->si_code);
get_user_ex(to->si_pid, &from->si_pid);
get_user_ex(to->si_uid, &from->si_uid);
get_user_ex(ptr32, &from->si_ptr);
to->si_ptr = compat_ptr(ptr32);
} get_user_catch(err);
return err;
}