lkml.org 
[lkml]   [2019]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[PATCH] signal/usb: Replace kill_pid_info_as_cred with kill_pid_usb_asyncio

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 */

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
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---

I managed to wrestle a sparc64 qemu to the ground so I could verify this
bug exists and the patch below fixes it.

Can I get an Ack from the usb side of things?

I intend to merge this through my siginfo tree unless someone objects.

Thank you,
Eric Biederman

drivers/usb/core/devio.c | 48 ++++++++++++-------------
include/linux/sched/signal.h | 2 +-
kernel/signal.c | 69 +++++++++++++++++++++++++++++++-----
3 files changed, 86 insertions(+), 33 deletions(-)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index fa783531ee88..a02448105527 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -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);
}
}

diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 38a0f0785323..c68ca81db0a1 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -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);
diff --git a/kernel/signal.c b/kernel/signal.c
index a1eb44dc9ff5..18040d6bd63a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -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)
--
2.17.1
\
 
 \ /
  Last update: 2019-05-21 14:41    [W:0.131 / U:2.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site