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Subject[PATCH 05/10] comedi: get rid of compat_alloc_user_space() mess in COMEDI_INSN compat
Date
From: Al Viro <viro@zeniv.linux.org.uk>

Just take copy_from_user() out of do_insn_ioctl() into the caller and
have compat_insn() build a native version and pass it to do_insn_ioctl()
directly.

One difference from the previous commits is that the helper used to
convert 32bit variant to native has two users - compat_insn() and
compat_insnlist(). The latter will be converted in next commit;
for now we simply split the helper in two variants - "userland 32bit
to kernel native" and "userland 32bit to userland native". The latter
is renamed old get_compat_insn(); it will be gone in the next commit.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
drivers/staging/comedi/comedi_fops.c | 73 +++++++++++++++++++++++-------------
1 file changed, 46 insertions(+), 27 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index d96dc85d8a98..ae0067ab5ead 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1615,22 +1615,19 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
* data (for reads) to insn->data pointer
*/
static int do_insn_ioctl(struct comedi_device *dev,
- struct comedi_insn __user *arg, void *file)
+ struct comedi_insn *insn, void *file)
{
- struct comedi_insn insn;
unsigned int *data = NULL;
unsigned int n_data = MIN_SAMPLES;
int ret = 0;

lockdep_assert_held(&dev->mutex);
- if (copy_from_user(&insn, arg, sizeof(insn)))
- return -EFAULT;

- n_data = max(n_data, insn.n);
+ n_data = max(n_data, insn->n);

/* This is where the behavior of insn and insnlist deviate. */
- if (insn.n > MAX_SAMPLES) {
- insn.n = MAX_SAMPLES;
+ if (insn->n > MAX_SAMPLES) {
+ insn->n = MAX_SAMPLES;
n_data = MAX_SAMPLES;
}

@@ -1640,26 +1637,26 @@ static int do_insn_ioctl(struct comedi_device *dev,
goto error;
}

- if (insn.insn & INSN_MASK_WRITE) {
+ if (insn->insn & INSN_MASK_WRITE) {
if (copy_from_user(data,
- insn.data,
- insn.n * sizeof(unsigned int))) {
+ insn->data,
+ insn->n * sizeof(unsigned int))) {
ret = -EFAULT;
goto error;
}
}
- ret = parse_insn(dev, &insn, data, file);
+ ret = parse_insn(dev, insn, data, file);
if (ret < 0)
goto error;
- if (insn.insn & INSN_MASK_READ) {
- if (copy_to_user(insn.data,
+ if (insn->insn & INSN_MASK_READ) {
+ if (copy_to_user(insn->data,
data,
- insn.n * sizeof(unsigned int))) {
+ insn->n * sizeof(unsigned int))) {
ret = -EFAULT;
goto error;
}
}
- ret = insn.n;
+ ret = insn->n;

error:
kfree(data);
@@ -2244,10 +2241,13 @@ static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
(struct comedi_insnlist __user *)arg,
file);
break;
- case COMEDI_INSN:
- rc = do_insn_ioctl(dev, (struct comedi_insn __user *)arg,
- file);
+ case COMEDI_INSN: {
+ struct comedi_insn insn;
+ if (copy_from_user(&insn, (void __user *)arg, sizeof(insn)))
+ rc = -EFAULT;
+ rc = do_insn_ioctl(dev, &insn, file);
break;
+ }
case COMEDI_POLL:
rc = do_poll_ioctl(dev, arg, file);
break;
@@ -3077,7 +3077,25 @@ static int compat_cmdtest(struct file *file, unsigned long arg)
}

/* Copy 32-bit insn structure to native insn structure. */
-static int get_compat_insn(struct comedi_insn __user *insn,
+static int get_compat_insn(struct comedi_insn *insn,
+ struct comedi32_insn_struct __user *insn32)
+{
+ struct comedi32_insn_struct v32;
+
+ /* Copy insn structure. Ignore the unused members. */
+ if (copy_from_user(&v32, insn32, sizeof(v32)))
+ return -EFAULT;
+ memset(insn, 0, sizeof(*insn));
+ insn->insn = v32.insn;
+ insn->n = v32.n;
+ insn->data = compat_ptr(v32.data);
+ insn->subdev = v32.subdev;
+ insn->chanspec = v32.chanspec;
+ return 0;
+}
+
+/* Copy 32-bit insn structure to native insn structure. */
+static int __get_compat_insn(struct comedi_insn __user *insn,
struct comedi32_insn_struct __user *insn32)
{
int err;
@@ -3146,7 +3164,7 @@ static int compat_insnlist(struct file *file, unsigned long arg)

/* Copy insn structures. */
for (n = 0; n < n_insns; n++) {
- rc = get_compat_insn(&s->insn[n], &insn32[n]);
+ rc = __get_compat_insn(&s->insn[n], &insn32[n]);
if (rc)
return rc;
}
@@ -3158,18 +3176,19 @@ static int compat_insnlist(struct file *file, unsigned long arg)
/* Handle 32-bit COMEDI_INSN ioctl. */
static int compat_insn(struct file *file, unsigned long arg)
{
- struct comedi_insn __user *insn;
- struct comedi32_insn_struct __user *insn32;
+ struct comedi_file *cfp = file->private_data;
+ struct comedi_device *dev = cfp->dev;
+ struct comedi_insn insn;
int rc;

- insn32 = compat_ptr(arg);
- insn = compat_alloc_user_space(sizeof(*insn));
-
- rc = get_compat_insn(insn, insn32);
+ rc = get_compat_insn(&insn, (void __user *)arg);
if (rc)
return rc;

- return comedi_unlocked_ioctl(file, COMEDI_INSN, (unsigned long)insn);
+ mutex_lock(&dev->mutex);
+ rc = do_insn_ioctl(dev, &insn, file);
+ mutex_unlock(&dev->mutex);
+ return rc;
}

/*
--
2.11.0
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