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SubjectRe: [PATCH] add missing checks of __copy_to_user return value in i2o_config.c
On Tue, 5 Oct 2004, Andrew Morton wrote:

> Jesper Juhl <juhl-lkml@dif.dk> wrote:
> >
> > - __copy_to_user(kxfer.buf, buffer.virt, fragsize);
> > + if (__copy_to_user(kxfer.buf, buffer.virt, fragsize)) {
> > + i2o_dma_free(&c->pdev->dev, &buffer);
> > + return -EFAULT;
> > + }
> > +
> > i2o_dma_free(&c->pdev->dev, &buffer);
>
> Please try to avoid more than a single return statement per function.
>
Will do. But this function already had a ton of return statements so I
assumed one more wouldn't make any real difference - I'll be sure to give
that more thought in the future.

> Also, please try to avoid duplicating code such as the above - it's a
> maintainance problem is nothing else.
>
> Like this:
>
> - __copy_to_user(kxfer.buf, buffer.virt, fragsize);
> + ret = 0;
> + if (__copy_to_user(kxfer.buf, buffer.virt, fragsize))
> + ret = -EFAULT;
> i2o_dma_free(&c->pdev->dev, &buffer);
> -
> - return 0;
> + return ret;
> };

Yes, that's what I had in mind when I noted a prettier version could be
made with a retval variable, the goto's I hinted at where intended to get
rid of the many return statements and create a single exit point for the
function. Your point about maintainability is noted.

How about just doing it all as in this patch below ?
I considered adding

return_nomem:
ret = -ENOMEM;
goto return_ret;

etc at the bottom as well, for the other return statements to use, but
that would be a lot of labels and gotos at the end, seems cleaner not to -
comments?

Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>

diff -up linux-2.6.9-rc3-bk5-orig/drivers/message/i2o/i2o_config.c linux-2.6.9-rc3-bk5/drivers/message/i2o/i2o_config.c
--- linux-2.6.9-rc3-bk5-orig/drivers/message/i2o/i2o_config.c 2004-09-30 05:05:40.000000000 +0200
+++ linux-2.6.9-rc3-bk5/drivers/message/i2o/i2o_config.c 2004-10-06 01:05:04.000000000 +0200
@@ -187,7 +187,8 @@ static int i2o_cfg_getiops(unsigned long
list_for_each_entry(c, &i2o_controllers, list)
tmp[c->unit] = 1;

- __copy_to_user(user_iop_table, tmp, MAX_I2O_CONTROLLERS);
+ if (__copy_to_user(user_iop_table, tmp, MAX_I2O_CONTROLLERS))
+ return -EFAULT;

return 0;
};
@@ -416,24 +417,25 @@ static int i2o_cfg_swul(unsigned long ar
u32 m;
unsigned int status = 0, swlen = 0, fragsize = 8192;
struct i2o_controller *c;
+ int ret = 0;

if (copy_from_user(&kxfer, pxfer, sizeof(struct i2o_sw_xfer)))
- return -EFAULT;
+ goto return_fault;

if (get_user(swlen, kxfer.swlen) < 0)
- return -EFAULT;
+ goto return_fault;

if (get_user(maxfrag, kxfer.maxfrag) < 0)
- return -EFAULT;
+ goto return_fault;

if (get_user(curfrag, kxfer.curfrag) < 0)
- return -EFAULT;
+ goto return_fault;

if (curfrag == maxfrag)
fragsize = swlen - (maxfrag - 1) * 8192;

if (!kxfer.buf || !access_ok(VERIFY_WRITE, kxfer.buf, fragsize))
- return -EFAULT;
+ goto return_fault;

c = i2o_find_iop(kxfer.iop);
if (!c)
@@ -474,10 +476,16 @@ static int i2o_cfg_swul(unsigned long ar
return status;
}

- __copy_to_user(kxfer.buf, buffer.virt, fragsize);
+ if (__copy_to_user(kxfer.buf, buffer.virt, fragsize))
+ ret = -EFAULT;
+
i2o_dma_free(&c->pdev->dev, &buffer);

- return 0;
+return_ret:
+ return ret;
+return_fault:
+ ret = -EFAULT;
+ goto return_ret;
};

static int i2o_cfg_swdel(unsigned long arg)

-
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