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authorDavid Herrmann <dh.herrmann@gmail.com>2018-11-14 14:16:42 +0100
committerJiri Kosina <jkosina@suse.cz>2018-11-19 14:32:27 +0100
commit4d26d1d1e8065bb3326a7c06d5d4698e581443a9 (patch)
treef1a9ff9487e6984b11310d08d43f37c207ee7b66 /drivers/hid
parent8c01db7619f07c85c5cd81ec5eb83608b56c88f5 (diff)
Revert "HID: uhid: use strlcpy() instead of strncpy()"
This reverts commit 336fd4f5f25157e9e8bd50e898a1bbcd99eaea46. Please note that `strlcpy()` does *NOT* do what you think it does. strlcpy() *ALWAYS* reads the full input string, regardless of the 'length' parameter. That is, if the input is not zero-terminated, strlcpy() will *READ* beyond input boundaries. It does this, because it always returns the size it *would* copy if the target was big enough, not the truncated size it actually copied. The original code was perfectly fine. The hid device is zero-initialized and the strncpy() functions copied up to n-1 characters. The result is always zero-terminated this way. This is the third time someone tried to replace strncpy with strlcpy in this function, and gets it wrong. I now added a comment that should at least make people reconsider. Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'drivers/hid')
-rw-r--r--drivers/hid/uhid.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 051639c09f72..840634e0f1e3 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -497,12 +497,13 @@ static int uhid_dev_create2(struct uhid_device *uhid,
goto err_free;
}
- len = min(sizeof(hid->name), sizeof(ev->u.create2.name));
- strlcpy(hid->name, ev->u.create2.name, len);
- len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys));
- strlcpy(hid->phys, ev->u.create2.phys, len);
- len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq));
- strlcpy(hid->uniq, ev->u.create2.uniq, len);
+ /* @hid is zero-initialized, strncpy() is correct, strlcpy() not */
+ len = min(sizeof(hid->name), sizeof(ev->u.create2.name)) - 1;
+ strncpy(hid->name, ev->u.create2.name, len);
+ len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys)) - 1;
+ strncpy(hid->phys, ev->u.create2.phys, len);
+ len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq)) - 1;
+ strncpy(hid->uniq, ev->u.create2.uniq, len);
hid->ll_driver = &uhid_hid_driver;
hid->bus = ev->u.create2.bus;