Re: [PATCH] hid: uhid.c: Cleaning up missing null-terminate in conjunction with strncpy
From: David Herrmann <hidden>
Date: 2014-07-28 08:32:05
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Hi On Sat, Jul 26, 2014 at 6:46 PM, Rickard Strandqvist [off-list ref] wrote:
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Replacing strncpy with strlcpy to avoid strings that lacks null terminate. And removed unnecessary magic numbers. Signed-off-by: Rickard Strandqvist <redacted> --- 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
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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