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signal: In sigqueueinfo prefer sig not si_signo

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Andrei Vagin <avagin@gmail.com> reported:

> Accoding to the man page, the user should not set si_signo, it has to be set
> by kernel.
>
> $ man 2 rt_sigqueueinfo
>
>     The uinfo argument specifies the data to accompany  the  signal.   This
>        argument  is  a  pointer to a structure of type siginfo_t, described in
>        sigaction(2) (and defined  by  including  <sigaction.h>).   The  caller
>        should set the following fields in this structure:
>
>        si_code
>               This  must  be  one of the SI_* codes in the Linux kernel source
>               file include/asm-generic/siginfo.h, with  the  restriction  that
>               the  code  must  be  negative (i.e., cannot be SI_USER, which is
>               used by the kernel to indicate a signal  sent  by  kill(2))  and
>               cannot  (since  Linux  2.6.39) be SI_TKILL (which is used by the
>               kernel to indicate a signal sent using tgkill(2)).
>
>        si_pid This should be set to a process ID, typically the process ID  of
>               the sender.
>
>        si_uid This  should  be set to a user ID, typically the real user ID of
>               the sender.
>
>        si_value
>               This field contains the user data to accompany the signal.   For
>               more information, see the description of the last (union sigval)
>               argument of sigqueue(3).
>
>        Internally, the kernel sets the si_signo field to the  value  specified
>        in  sig,  so that the receiver of the signal can also obtain the signal
>        number via that field.
>
> On Tue, Sep 25, 2018 at 07:19:02PM +0200, Eric W. Biederman wrote:
>>
>> If there is some application that calls sigqueueinfo directly that has
>> a problem with this added sanity check we can revisit this when we see
>> what kind of crazy that application is doing.
>
>
> I already know two "applications" ;)
>
> https://github.com/torvalds/linux/blob/master/tools/testing/selftests/ptrace/peeksiginfo.c
> https://github.com/checkpoint-restore/criu/blob/master/test/zdtm/static/sigpending.c
>
> Disclaimer: I'm the author of both of them.

Looking at the kernel code the historical behavior has alwasy been to prefer
the signal number passed in by the kernel.

So sigh.  Implmenet __copy_siginfo_from_user and __copy_siginfo_from_user32 to
take that signal number and prefer it.  The user of ptrace will still
use copy_siginfo_from_user and copy_siginfo_from_user32 as they do not and
never have had a signal number there.

Luckily this change has never made it farther than linux-next.

Fixes: e75dc036c4 ("signal: Fail sigqueueinfo if si_signo != sig")
Reported-by: Andrei Vagin <avagin@gmail.com>
Tested-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2018-10-05 09:02:48 +02:00
parent 4ce5f9c9e7
commit 601d5abfea
1 changed files with 114 additions and 87 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

201
kernel/signal.c
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@ -2925,11 +2925,10 @@ int copy_siginfo_to_user(siginfo_t __user *to, const kernel_siginfo_t *from)
return 0;
}
int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from)
static int post_copy_siginfo_from_user(kernel_siginfo_t *info,
const siginfo_t __user *from)
{
if (copy_from_user(to, from, sizeof(struct kernel_siginfo)))
return -EFAULT;
if (unlikely(!known_siginfo_layout(to->si_signo, to->si_code))) {
if (unlikely(!known_siginfo_layout(info->si_signo, info->si_code))) {
char __user *expansion = si_expansion(from);
char buf[SI_EXPANSION_SIZE];
int i;
@ -2949,6 +2948,22 @@ int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from)
return 0;
}
static int __copy_siginfo_from_user(int signo, kernel_siginfo_t *to,
const siginfo_t __user *from)
{
if (copy_from_user(to, from, sizeof(struct kernel_siginfo)))
return -EFAULT;
to->si_signo = signo;
return post_copy_siginfo_from_user(to, from);
}
int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from)
{
if (copy_from_user(to, from, sizeof(struct kernel_siginfo)))
return -EFAULT;
return post_copy_siginfo_from_user(to, from);
}
#ifdef CONFIG_COMPAT
int copy_siginfo_to_user32(struct compat_siginfo __user *to,
const struct kernel_siginfo *from)
@ -3041,6 +3056,96 @@ int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
return 0;
}
static int post_copy_siginfo_from_user32(kernel_siginfo_t *to,
const struct compat_siginfo *from)
{
clear_siginfo(to);
to->si_signo = from->si_signo;
to->si_errno = from->si_errno;
to->si_code = from->si_code;
switch(siginfo_layout(from->si_signo, from->si_code)) {
case SIL_KILL:
to->si_pid = from->si_pid;
to->si_uid = from->si_uid;
break;
case SIL_TIMER:
to->si_tid = from->si_tid;
to->si_overrun = from->si_overrun;
to->si_int = from->si_int;
break;
case SIL_POLL:
to->si_band = from->si_band;
to->si_fd = from->si_fd;
break;
case SIL_FAULT:
to->si_addr = compat_ptr(from->si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from->si_trapno;
#endif
break;
case SIL_FAULT_MCEERR:
to->si_addr = compat_ptr(from->si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from->si_trapno;
#endif
to->si_addr_lsb = from->si_addr_lsb;
break;
case SIL_FAULT_BNDERR:
to->si_addr = compat_ptr(from->si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from->si_trapno;
#endif
to->si_lower = compat_ptr(from->si_lower);
to->si_upper = compat_ptr(from->si_upper);
break;
case SIL_FAULT_PKUERR:
to->si_addr = compat_ptr(from->si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from->si_trapno;
#endif
to->si_pkey = from->si_pkey;
break;
case SIL_CHLD:
to->si_pid = from->si_pid;
to->si_uid = from->si_uid;
to->si_status = from->si_status;
#ifdef CONFIG_X86_X32_ABI
if (in_x32_syscall()) {
to->si_utime = from->_sifields._sigchld_x32._utime;
to->si_stime = from->_sifields._sigchld_x32._stime;
} else
#endif
{
to->si_utime = from->si_utime;
to->si_stime = from->si_stime;
}
break;
case SIL_RT:
to->si_pid = from->si_pid;
to->si_uid = from->si_uid;
to->si_int = from->si_int;
break;
case SIL_SYS:
to->si_call_addr = compat_ptr(from->si_call_addr);
to->si_syscall = from->si_syscall;
to->si_arch = from->si_arch;
break;
}
return 0;
}
static int __copy_siginfo_from_user32(int signo, struct kernel_siginfo *to,
const struct compat_siginfo __user *ufrom)
{
struct compat_siginfo from;
if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo)))
return -EFAULT;
from.si_signo = signo;
return post_copy_siginfo_from_user32(to, &from);
}
int copy_siginfo_from_user32(struct kernel_siginfo *to,
const struct compat_siginfo __user *ufrom)
{
@ -3049,79 +3154,7 @@ int copy_siginfo_from_user32(struct kernel_siginfo *to,
if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo)))
return -EFAULT;
clear_siginfo(to);
to->si_signo = from.si_signo;
to->si_errno = from.si_errno;
to->si_code = from.si_code;
switch(siginfo_layout(from.si_signo, from.si_code)) {
case SIL_KILL:
to->si_pid = from.si_pid;
to->si_uid = from.si_uid;
break;
case SIL_TIMER:
to->si_tid = from.si_tid;
to->si_overrun = from.si_overrun;
to->si_int = from.si_int;
break;
case SIL_POLL:
to->si_band = from.si_band;
to->si_fd = from.si_fd;
break;
case SIL_FAULT:
to->si_addr = compat_ptr(from.si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from.si_trapno;
#endif
break;
case SIL_FAULT_MCEERR:
to->si_addr = compat_ptr(from.si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from.si_trapno;
#endif
to->si_addr_lsb = from.si_addr_lsb;
break;
case SIL_FAULT_BNDERR:
to->si_addr = compat_ptr(from.si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from.si_trapno;
#endif
to->si_lower = compat_ptr(from.si_lower);
to->si_upper = compat_ptr(from.si_upper);
break;
case SIL_FAULT_PKUERR:
to->si_addr = compat_ptr(from.si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from.si_trapno;
#endif
to->si_pkey = from.si_pkey;
break;
case SIL_CHLD:
to->si_pid = from.si_pid;
to->si_uid = from.si_uid;
to->si_status = from.si_status;
#ifdef CONFIG_X86_X32_ABI
if (in_x32_syscall()) {
to->si_utime = from._sifields._sigchld_x32._utime;
to->si_stime = from._sifields._sigchld_x32._stime;
} else
#endif
{
to->si_utime = from.si_utime;
to->si_stime = from.si_stime;
}
break;
case SIL_RT:
to->si_pid = from.si_pid;
to->si_uid = from.si_uid;
to->si_int = from.si_int;
break;
case SIL_SYS:
to->si_call_addr = compat_ptr(from.si_call_addr);
to->si_syscall = from.si_syscall;
to->si_arch = from.si_arch;
break;
}
return 0;
return post_copy_siginfo_from_user32(to, &from);
}
#endif /* CONFIG_COMPAT */
@ -3359,9 +3392,6 @@ static int do_rt_sigqueueinfo(pid_t pid, int sig, kernel_siginfo_t *info)
(task_pid_vnr(current) != pid))
return -EPERM;
if (info->si_signo != sig)
return -EINVAL;
/* POSIX.1b doesn't mention process groups. */
return kill_proc_info(sig, info, pid);
}
@ -3376,7 +3406,7 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
siginfo_t __user *, uinfo)
{
kernel_siginfo_t info;
int ret = copy_siginfo_from_user(&info, uinfo);
int ret = __copy_siginfo_from_user(sig, &info, uinfo);
if (unlikely(ret))
return ret;
return do_rt_sigqueueinfo(pid, sig, &info);
@ -3389,7 +3419,7 @@ COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo,
struct compat_siginfo __user *, uinfo)
{
kernel_siginfo_t info;
int ret = copy_siginfo_from_user32(&info, uinfo);
int ret = __copy_siginfo_from_user32(sig, &info, uinfo);
if (unlikely(ret))
return ret;
return do_rt_sigqueueinfo(pid, sig, &info);
@ -3409,9 +3439,6 @@ static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, kernel_siginfo_t
(task_pid_vnr(current) != pid))
return -EPERM;
if (info->si_signo != sig)
return -EINVAL;
return do_send_specific(tgid, pid, sig, info);
}
@ -3419,7 +3446,7 @@ SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
siginfo_t __user *, uinfo)
{
kernel_siginfo_t info;
int ret = copy_siginfo_from_user(&info, uinfo);
int ret = __copy_siginfo_from_user(sig, &info, uinfo);
if (unlikely(ret))
return ret;
return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
@ -3433,7 +3460,7 @@ COMPAT_SYSCALL_DEFINE4(rt_tgsigqueueinfo,
struct compat_siginfo __user *, uinfo)
{
kernel_siginfo_t info;
int ret = copy_siginfo_from_user32(&info, uinfo);
int ret = __copy_siginfo_from_user32(sig, &info, uinfo);
if (unlikely(ret))
return ret;
return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);