[PATCH] platform/x86: think-lmi: Prevent underflow in index_store()

There needs to be a check to prevent negative offsets for
setting->index.  I have reviewed this code and I think that the
"if (block->instance_count <= instance)" check in __query_block() will
prevent this from resulting in an out of bounds access.  But it's
still worth fixing.

Fixes: 640a5fa50a42 ("platform/x86: think-lmi: Opcode support")
Signed-off-by: Dan Carpenter <redacted>
---
 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 27ab8e4e5b83..0b73e16cccea 100644
--- a/drivers/platform/x86/think-lmi.c
+++ b/drivers/platform/x86/think-lmi.c

@@ -573,7 +573,7 @@ static ssize_t index_store(struct kobject *kobj,
 	if (err < 0)
 		return err;
 
-	if (val > TLMI_INDEX_MAX)
+	if (val < 0 || val > TLMI_INDEX_MAX)
 		return -EINVAL;
 
 	setting->index = val;

-- 
2.20.1

Thanks Dan

On 2021-12-17 02:12, Dan Carpenter wrote:

Agreed, it's good to have this check.
Thank you
Mark

Hi,

On 12/17/21 08:12, Dan Carpenter wrote:

There needs to be a check to prevent negative offsets for
setting->index.  I have reviewed this code and I think that the
"if (block->instance_count <= instance)" check in __query_block() will
prevent this from resulting in an out of bounds access.  But it's
still worth fixing.

Fixes: 640a5fa50a42 ("platform/x86: think-lmi: Opcode support")
Signed-off-by: Dan Carpenter <redacted>

Thank you for your patch, I've applied this patch to my review-hans 
branch:
https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=review-hans

Note it will show up in my review-hans branch once I've pushed my
local branch there, which might take a while.

Once I've run some tests on this branch the patches there will be
added to the platform-drivers-x86/for-next branch and eventually
will be included in the pdx86 pull-request to Linus for the next
merge-window.

Regards,

Hans