Commit 0ddcf3a6b442 ("platform/x86: think-lmi: Avoid potential read before
start of the buffer") moved the lengt == 0 up to before stripping the '\n'
which typically gets added when users echo a value to a sysfs-attribute
from the shell.
This avoids a potential buffer-underrun, but it also causes a behavioral
change, prior to this change "echo > kbdlang", iow writing just a single
'\n' would result in an EINVAL error, but after the change this gets
accepted setting kbdlang to an empty string.
Re-add the length != 0 check after stripping the '\n' to reject this
again, as before the change.
Fixes: 0ddcf3a6b442 ("platform/x86: think-lmi: Avoid potential read before start of the buffer")
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
drivers/platform/x86/think-lmi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/x86/think-lmi.c b/drivers/platform/x86/think-lmi.c
index c6c9fbb8a53e..c22435acebbe 100644
--- a/drivers/platform/x86/think-lmi.c
+++ b/drivers/platform/x86/think-lmi.c
@@ -449,7 +449,7 @@ static ssize_t kbdlang_store(struct kobject *kobj,
if (buf[length-1] == '\n')
length--;
- if (length >= TLMI_LANG_MAXLEN)
+ if (!length || length >= TLMI_LANG_MAXLEN)
return -EINVAL;
memcpy(setting->kbdlang, buf, length);
--
2.31.1
