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signal/usb: Replace kill_pid_info_as_cred with kill_pid_usb_asyncio

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The usb support for asyncio encoded one of it's values in the wrong
field.  It should have used si_value but instead used si_addr which is
not present in the _rt union member of struct siginfo.

The practical result of this is that on a 64bit big endian kernel
when delivering a signal to a 32bit process the si_addr field
is set to NULL, instead of the expected pointer value.

This issue can not be fixed in copy_siginfo_to_user32 as the usb
usage of the the _sigfault (aka si_addr) member of the siginfo
union when SI_ASYNCIO is set is incompatible with the POSIX and
glibc usage of the _rt member of the siginfo union.

Therefore replace kill_pid_info_as_cred with kill_pid_usb_asyncio a
dedicated function for this one specific case.  There are no other
users of kill_pid_info_as_cred so this specialization should have no
impact on the amount of code in the kernel.  Have kill_pid_usb_asyncio
take instead of a siginfo_t which is difficult and error prone, 3
arguments, a signal number, an errno value, and an address enconded as
a sigval_t.  The encoding of the address as a sigval_t allows the
code that reads the userspace request for a signal to handle this
compat issue along with all of the other compat issues.

Add BUILD_BUG_ONs in kernel/signal.c to ensure that we can now place
the pointer value at the in si_pid (instead of si_addr).  That is the
code now verifies that si_pid and si_addr always occur at the same
location.  Further the code veries that for native structures a value
placed in si_pid and spilling into si_uid will appear in userspace in
si_addr (on a byte by byte copy of siginfo or a field by field copy of
siginfo).  The code also verifies that for a 64bit kernel and a 32bit
userspace the 32bit pointer will fit in si_pid.

I have used the usbsig.c program below written by Alan Stern and
slightly tweaked by me to run on a big endian machine to verify the
issue exists (on sparc64) and to confirm the patch below fixes the issue.

 /* usbsig.c -- test USB async signal delivery */

 #define _GNU_SOURCE
 #include <stdio.h>
 #include <fcntl.h>
 #include <signal.h>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <unistd.h>
 #include <endian.h>
 #include <linux/usb/ch9.h>
 #include <linux/usbdevice_fs.h>

 static struct usbdevfs_urb urb;
 static struct usbdevfs_disconnectsignal ds;
 static volatile sig_atomic_t done = 0;

 void urb_handler(int sig, siginfo_t *info , void *ucontext)
 {
 	printf("Got signal %d, signo %d errno %d code %d addr: %p urb: %p\n",
 	       sig, info->si_signo, info->si_errno, info->si_code,
 	       info->si_addr, &urb);

 	printf("%s\n", (info->si_addr == &urb) ? "Good" : "Bad");
 }

 void ds_handler(int sig, siginfo_t *info , void *ucontext)
 {
 	printf("Got signal %d, signo %d errno %d code %d addr: %p ds: %p\n",
 	       sig, info->si_signo, info->si_errno, info->si_code,
 	       info->si_addr, &ds);

 	printf("%s\n", (info->si_addr == &ds) ? "Good" : "Bad");
 	done = 1;
 }

 int main(int argc, char **argv)
 {
 	char *devfilename;
 	int fd;
 	int rc;
 	struct sigaction act;
 	struct usb_ctrlrequest *req;
 	void *ptr;
 	char buf[80];

 	if (argc != 2) {
 		fprintf(stderr, "Usage: usbsig device-file-name\n");
 		return 1;
 	}

 	devfilename = argv[1];
 	fd = open(devfilename, O_RDWR);
 	if (fd == -1) {
 		perror("Error opening device file");
 		return 1;
 	}

 	act.sa_sigaction = urb_handler;
 	sigemptyset(&act.sa_mask);
 	act.sa_flags = SA_SIGINFO;

 	rc = sigaction(SIGUSR1, &act, NULL);
 	if (rc == -1) {
 		perror("Error in sigaction");
 		return 1;
 	}

 	act.sa_sigaction = ds_handler;
 	sigemptyset(&act.sa_mask);
 	act.sa_flags = SA_SIGINFO;

 	rc = sigaction(SIGUSR2, &act, NULL);
 	if (rc == -1) {
 		perror("Error in sigaction");
 		return 1;
 	}

 	memset(&urb, 0, sizeof(urb));
 	urb.type = USBDEVFS_URB_TYPE_CONTROL;
 	urb.endpoint = USB_DIR_IN | 0;
 	urb.buffer = buf;
 	urb.buffer_length = sizeof(buf);
 	urb.signr = SIGUSR1;

 	req = (struct usb_ctrlrequest *) buf;
 	req->bRequestType = USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE;
 	req->bRequest = USB_REQ_GET_DESCRIPTOR;
 	req->wValue = htole16(USB_DT_DEVICE << 8);
 	req->wIndex = htole16(0);
 	req->wLength = htole16(sizeof(buf) - sizeof(*req));

 	rc = ioctl(fd, USBDEVFS_SUBMITURB, &urb);
 	if (rc == -1) {
 		perror("Error in SUBMITURB ioctl");
 		return 1;
 	}

 	rc = ioctl(fd, USBDEVFS_REAPURB, &ptr);
 	if (rc == -1) {
 		perror("Error in REAPURB ioctl");
 		return 1;
 	}

 	memset(&ds, 0, sizeof(ds));
 	ds.signr = SIGUSR2;
 	ds.context = &ds;
 	rc = ioctl(fd, USBDEVFS_DISCSIGNAL, &ds);
 	if (rc == -1) {
 		perror("Error in DISCSIGNAL ioctl");
 		return 1;
 	}

 	printf("Waiting for usb disconnect\n");
 	while (!done) {
 		sleep(1);
 	}

 	close(fd);
 	return 0;
 }

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Oliver Neukum <oneukum@suse.com>
Fixes: v2.3.39
Cc: stable@vger.kernel.org
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2019-02-07 19:44:12 -06:00
parent a188339ca5
commit 70f1b0d34b
3 changed files with 86 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
drivers/usb/core/devio.c
View File

@ -63,7 +63,7 @@ struct usb_dev_state {
unsigned int discsignr;
struct pid *disc_pid;
const struct cred *cred;
void __user *disccontext;
sigval_t disccontext;
unsigned long ifclaimed;
u32 disabled_bulk_eps;
bool privileges_dropped;
@ -90,6 +90,7 @@ struct async {
unsigned int ifnum;
void __user *userbuffer;
void __user *userurb;
sigval_t userurb_sigval;
struct urb *urb;
struct usb_memory *usbm;
unsigned int mem_usage;
@ -582,22 +583,19 @@ static void async_completed(struct urb *urb)
{
struct async *as = urb->context;
struct usb_dev_state *ps = as->ps;
struct kernel_siginfo sinfo;
struct pid *pid = NULL;
const struct cred *cred = NULL;
unsigned long flags;
int signr;
sigval_t addr;
int signr, errno;
spin_lock_irqsave(&ps->lock, flags);
list_move_tail(&as->asynclist, &ps->async_completed);
as->status = urb->status;
signr = as->signr;
if (signr) {
clear_siginfo(&sinfo);
sinfo.si_signo = as->signr;
sinfo.si_errno = as->status;
sinfo.si_code = SI_ASYNCIO;
sinfo.si_addr = as->userurb;
errno = as->status;
addr = as->userurb_sigval;
pid = get_pid(as->pid);
cred = get_cred(as->cred);
}
@ -615,7 +613,7 @@ static void async_completed(struct urb *urb)
spin_unlock_irqrestore(&ps->lock, flags);
if (signr) {
kill_pid_info_as_cred(sinfo.si_signo, &sinfo, pid, cred);
kill_pid_usb_asyncio(signr, errno, addr, pid, cred);
put_pid(pid);
put_cred(cred);
}
@ -1427,7 +1425,7 @@ find_memory_area(struct usb_dev_state *ps, const struct usbdevfs_urb *uurb)
static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb,
struct usbdevfs_iso_packet_desc __user *iso_frame_desc,
void __user *arg)
void __user *arg, sigval_t userurb_sigval)
{
struct usbdevfs_iso_packet_desc *isopkt = NULL;
struct usb_host_endpoint *ep;
@ -1727,6 +1725,7 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
isopkt = NULL;
as->ps = ps;
as->userurb = arg;
as->userurb_sigval = userurb_sigval;
if (as->usbm) {
unsigned long uurb_start = (unsigned long)uurb->buffer;
@ -1801,13 +1800,17 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
static int proc_submiturb(struct usb_dev_state *ps, void __user *arg)
{
struct usbdevfs_urb uurb;
sigval_t userurb_sigval;
if (copy_from_user(&uurb, arg, sizeof(uurb)))
return -EFAULT;
memset(&userurb_sigval, 0, sizeof(userurb_sigval));
userurb_sigval.sival_ptr = arg;
return proc_do_submiturb(ps, &uurb,
(((struct usbdevfs_urb __user *)arg)->iso_frame_desc),
arg);
arg, userurb_sigval);
}
static int proc_unlinkurb(struct usb_dev_state *ps, void __user *arg)
@ -1977,7 +1980,7 @@ static int proc_disconnectsignal_compat(struct usb_dev_state *ps, void __user *a
if (copy_from_user(&ds, arg, sizeof(ds)))
return -EFAULT;
ps->discsignr = ds.signr;
ps->disccontext = compat_ptr(ds.context);
ps->disccontext.sival_int = ds.context;
return 0;
}
@ -2005,13 +2008,17 @@ static int get_urb32(struct usbdevfs_urb *kurb,
static int proc_submiturb_compat(struct usb_dev_state *ps, void __user *arg)
{
struct usbdevfs_urb uurb;
sigval_t userurb_sigval;
if (get_urb32(&uurb, (struct usbdevfs_urb32 __user *)arg))
return -EFAULT;
memset(&userurb_sigval, 0, sizeof(userurb_sigval));
userurb_sigval.sival_int = ptr_to_compat(arg);
return proc_do_submiturb(ps, &uurb,
((struct usbdevfs_urb32 __user *)arg)->iso_frame_desc,
arg);
arg, userurb_sigval);
}
static int processcompl_compat(struct async *as, void __user * __user *arg)
@ -2092,7 +2099,7 @@ static int proc_disconnectsignal(struct usb_dev_state *ps, void __user *arg)
if (copy_from_user(&ds, arg, sizeof(ds)))
return -EFAULT;
ps->discsignr = ds.signr;
ps->disccontext = ds.context;
ps->disccontext.sival_ptr = ds.context;
return 0;
}
@ -2614,22 +2621,15 @@ const struct file_operations usbdev_file_operations = {
static void usbdev_remove(struct usb_device *udev)
{
struct usb_dev_state *ps;
struct kernel_siginfo sinfo;
while (!list_empty(&udev->filelist)) {
ps = list_entry(udev->filelist.next, struct usb_dev_state, list);
destroy_all_async(ps);
wake_up_all(&ps->wait);
list_del_init(&ps->list);
if (ps->discsignr) {
clear_siginfo(&sinfo);
sinfo.si_signo = ps->discsignr;
sinfo.si_errno = EPIPE;
sinfo.si_code = SI_ASYNCIO;
sinfo.si_addr = ps->disccontext;
kill_pid_info_as_cred(ps->discsignr, &sinfo,
ps->disc_pid, ps->cred);
}
if (ps->discsignr)
kill_pid_usb_asyncio(ps->discsignr, EPIPE, ps->disccontext,
ps->disc_pid, ps->cred);
}
}

2
include/linux/sched/signal.h
View File

@ -329,7 +329,7 @@ extern void force_sigsegv(int sig, struct task_struct *p);
extern int force_sig_info(int, struct kernel_siginfo *, struct task_struct *);
extern int __kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp);
extern int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid);
extern int kill_pid_info_as_cred(int, struct kernel_siginfo *, struct pid *,
extern int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr, struct pid *,
const struct cred *);
extern int kill_pgrp(struct pid *pid, int sig, int priv);
extern int kill_pid(struct pid *pid, int sig, int priv);

69
kernel/signal.c
View File

@ -1439,13 +1439,44 @@ static inline bool kill_as_cred_perm(const struct cred *cred,
uid_eq(cred->uid, pcred->uid);
}
/* like kill_pid_info(), but doesn't use uid/euid of "current" */
int kill_pid_info_as_cred(int sig, struct kernel_siginfo *info, struct pid *pid,
const struct cred *cred)
/*
* The usb asyncio usage of siginfo is wrong. The glibc support
* for asyncio which uses SI_ASYNCIO assumes the layout is SIL_RT.
* AKA after the generic fields:
* kernel_pid_t si_pid;
* kernel_uid32_t si_uid;
* sigval_t si_value;
*
* Unfortunately when usb generates SI_ASYNCIO it assumes the layout
* after the generic fields is:
* void __user *si_addr;
*
* This is a practical problem when there is a 64bit big endian kernel
* and a 32bit userspace. As the 32bit address will encoded in the low
* 32bits of the pointer. Those low 32bits will be stored at higher
* address than appear in a 32 bit pointer. So userspace will not
* see the address it was expecting for it's completions.
*
* There is nothing in the encoding that can allow
* copy_siginfo_to_user32 to detect this confusion of formats, so
* handle this by requiring the caller of kill_pid_usb_asyncio to
* notice when this situration takes place and to store the 32bit
* pointer in sival_int, instead of sival_addr of the sigval_t addr
* parameter.
*/
int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr,
struct pid *pid, const struct cred *cred)
{
int ret = -EINVAL;
struct kernel_siginfo info;
struct task_struct *p;
unsigned long flags;
int ret = -EINVAL;
clear_siginfo(&info);
info.si_signo = sig;
info.si_errno = errno;
info.si_code = SI_ASYNCIO;
*((sigval_t *)&info.si_pid) = addr;
if (!valid_signal(sig))
return ret;
@ -1456,17 +1487,17 @@ int kill_pid_info_as_cred(int sig, struct kernel_siginfo *info, struct pid *pid,
ret = -ESRCH;
goto out_unlock;
}
if (si_fromuser(info) && !kill_as_cred_perm(cred, p)) {
if (!kill_as_cred_perm(cred, p)) {
ret = -EPERM;
goto out_unlock;
}
ret = security_task_kill(p, info, sig, cred);
ret = security_task_kill(p, &info, sig, cred);
if (ret)
goto out_unlock;
if (sig) {
if (lock_task_sighand(p, &flags)) {
ret = __send_signal(sig, info, p, PIDTYPE_TGID, 0);
ret = __send_signal(sig, &info, p, PIDTYPE_TGID, 0);
unlock_task_sighand(p, &flags);
} else
ret = -ESRCH;
@ -1475,7 +1506,7 @@ int kill_pid_info_as_cred(int sig, struct kernel_siginfo *info, struct pid *pid,
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL_GPL(kill_pid_info_as_cred);
EXPORT_SYMBOL_GPL(kill_pid_usb_asyncio);
/*
* kill_something_info() interprets pid in interesting ways just like kill(2).
@ -4474,6 +4505,28 @@ static inline void siginfo_buildtime_checks(void)
CHECK_OFFSET(si_syscall);
CHECK_OFFSET(si_arch);
#undef CHECK_OFFSET
/* usb asyncio */
BUILD_BUG_ON(offsetof(struct siginfo, si_pid) !=
offsetof(struct siginfo, si_addr));
if (sizeof(int) == sizeof(void __user *)) {
BUILD_BUG_ON(sizeof_field(struct siginfo, si_pid) !=
sizeof(void __user *));
} else {
BUILD_BUG_ON((sizeof_field(struct siginfo, si_pid) +
sizeof_field(struct siginfo, si_uid)) !=
sizeof(void __user *));
BUILD_BUG_ON(offsetofend(struct siginfo, si_pid) !=
offsetof(struct siginfo, si_uid));
}
#ifdef CONFIG_COMPAT
BUILD_BUG_ON(offsetof(struct compat_siginfo, si_pid) !=
offsetof(struct compat_siginfo, si_addr));
BUILD_BUG_ON(sizeof_field(struct compat_siginfo, si_pid) !=
sizeof(compat_uptr_t));
BUILD_BUG_ON(sizeof_field(struct compat_siginfo, si_pid) !=
sizeof_field(struct siginfo, si_pid));
#endif
}
void __init signals_init(void)