Commit 601d5abf authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

signal: In sigqueueinfo prefer sig not si_signo 

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: e75dc036 ("signal: Fail sigqueueinfo if si_signo != sig")
Reported-by: default avatarAndrei Vagin <avagin@gmail.com>
Tested-by: default avatarAndrei Vagin <avagin@gmail.com>
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 4ce5f9c9

kernel/signal.c

+84 −57
Original line number Diff line number Diff line
@@ -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)
@@ -3041,88 +3056,106 @@ int __copy_siginfo_to_user32(struct compat_siginfo __user *to, 
	return 0;

}



int copy_siginfo_from_user32(struct kernel_siginfo *to,

			     const struct compat_siginfo __user *ufrom)

static int post_copy_siginfo_from_user32(kernel_siginfo_t *to,

					 const struct compat_siginfo *from)

{

	struct compat_siginfo from;



	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)) {

	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;

		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;

		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;

		to->si_band = from->si_band;

		to->si_fd   = from->si_fd;

		break;

	case SIL_FAULT:

		to->si_addr = compat_ptr(from.si_addr);

		to->si_addr = compat_ptr(from->si_addr);

#ifdef __ARCH_SI_TRAPNO

		to->si_trapno = from.si_trapno;

		to->si_trapno = from->si_trapno;

#endif

		break;

	case SIL_FAULT_MCEERR:

		to->si_addr = compat_ptr(from.si_addr);

		to->si_addr = compat_ptr(from->si_addr);

#ifdef __ARCH_SI_TRAPNO

		to->si_trapno = from.si_trapno;

		to->si_trapno = from->si_trapno;

#endif

		to->si_addr_lsb = from.si_addr_lsb;

		to->si_addr_lsb = from->si_addr_lsb;

		break;

	case SIL_FAULT_BNDERR:

		to->si_addr = compat_ptr(from.si_addr);

		to->si_addr = compat_ptr(from->si_addr);

#ifdef __ARCH_SI_TRAPNO

		to->si_trapno = from.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);

		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);

		to->si_addr = compat_ptr(from->si_addr);

#ifdef __ARCH_SI_TRAPNO

		to->si_trapno = from.si_trapno;

		to->si_trapno = from->si_trapno;

#endif

		to->si_pkey = from.si_pkey;

		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;

		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;

			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;

			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;

		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;

		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)

{

	struct compat_siginfo from;



	if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo)))

		return -EFAULT;



	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);

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