2014-07-26 16:45:16

by Rickard Strandqvist

Subject: [PATCH] hid: uhid.c: Cleaning up missing null-terminate in conjunction with strncpy

Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
And removed unnecessary magic numbers.

Signed-off-by: Rickard Strandqvist <[email protected]>
---
drivers/hid/uhid.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 0cb92e3..b72ab0c 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -392,12 +392,9 @@ static int uhid_dev_create(struct uhid_device *uhid,
goto err_free;
}

- strncpy(hid->name, ev->u.create.name, 127);
- hid->name[127] = 0;
- strncpy(hid->phys, ev->u.create.phys, 63);
- hid->phys[63] = 0;
- strncpy(hid->uniq, ev->u.create.uniq, 63);
- hid->uniq[63] = 0;
+ strlcpy(hid->name, ev->u.create.name, sizeof(hid->name));
+ strlcpy(hid->phys, ev->u.create.phys, sizeof(hid->phys));
+ strlcpy(hid->uniq, ev->u.create.uniq, sizeof(hid->uniq));

hid->ll_driver = &uhid_hid_driver;
hid->bus = ev->u.create.bus;
@@ -452,12 +449,9 @@ static int uhid_dev_create2(struct uhid_device *uhid,
goto err_free;
}

- strncpy(hid->name, ev->u.create2.name, 127);
- hid->name[127] = 0;
- strncpy(hid->phys, ev->u.create2.phys, 63);
- hid->phys[63] = 0;
- strncpy(hid->uniq, ev->u.create2.uniq, 63);
- hid->uniq[63] = 0;
+ strlcpy(hid->name, ev->u.create2.name, sizeof(hid->name));
+ strlcpy(hid->phys, ev->u.create2.phys, sizeof(hid->phys));
+ strlcpy(hid->uniq, ev->u.create2.uniq, sizeof(hid->uniq));

hid->ll_driver = &uhid_hid_driver;
hid->bus = ev->u.create2.bus;
--
1.7.10.4

2014-07-28 08:32:05

by David Herrmann

Subject: Re: [PATCH] hid: uhid.c: Cleaning up missing null-terminate in conjunction with strncpy

Hi

On Sat, Jul 26, 2014 at 6:46 PM, Rickard Strandqvist
<[email protected]> wrote:
> Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
> And removed unnecessary magic numbers.
>
> Signed-off-by: Rickard Strandqvist <[email protected]>
> ---
> drivers/hid/uhid.c | 18 ++++++------------
> 1 file changed, 6 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
> index 0cb92e3..b72ab0c 100644
> --- a/drivers/hid/uhid.c
> +++ b/drivers/hid/uhid.c
> @@ -392,12 +392,9 @@ static int uhid_dev_create(struct uhid_device *uhid,
> goto err_free;
> }
>
> - strncpy(hid->name, ev->u.create.name, 127);
> - hid->name[127] = 0;
> - strncpy(hid->phys, ev->u.create.phys, 63);
> - hid->phys[63] = 0;
> - strncpy(hid->uniq, ev->u.create.uniq, 63);
> - hid->uniq[63] = 0;
> + strlcpy(hid->name, ev->u.create.name, sizeof(hid->name));
> + strlcpy(hid->phys, ev->u.create.phys, sizeof(hid->phys));
> + strlcpy(hid->uniq, ev->u.create.uniq, sizeof(hid->uniq));

NAK, this patch is wrong. strlcpy() is *not* a replacement for
strncpy(). Please see lib/string.c or the man-page of strlcpy(3). It
calls strlen() on the source, which strncpy() does not. "ev" was
copied unmodified from user-space and might not be NULL-terminated,
therefore, strncpy() is the right choice.

Btw., please avoid commit-messages that sound like bug-fixes, which
this definitely is not. hid_allocate_device() cleans the object to
ZERO, therefore, you're guaranteed that there's a proper
NULL-terminator, independent of the contents of ev->u.xyz.

Thanks
David

> hid->ll_driver = &uhid_hid_driver;
> hid->bus = ev->u.create.bus;
> @@ -452,12 +449,9 @@ static int uhid_dev_create2(struct uhid_device *uhid,
> goto err_free;
> }
>
> - strncpy(hid->name, ev->u.create2.name, 127);
> - hid->name[127] = 0;
> - strncpy(hid->phys, ev->u.create2.phys, 63);
> - hid->phys[63] = 0;
> - strncpy(hid->uniq, ev->u.create2.uniq, 63);
> - hid->uniq[63] = 0;
> + strlcpy(hid->name, ev->u.create2.name, sizeof(hid->name));
> + strlcpy(hid->phys, ev->u.create2.phys, sizeof(hid->phys));
> + strlcpy(hid->uniq, ev->u.create2.uniq, sizeof(hid->uniq));
>
> hid->ll_driver = &uhid_hid_driver;
> hid->bus = ev->u.create2.bus;
> --
> 1.7.10.4
>