Re: [PATCH v2] x86/microcode: Silence a static checker warning

From: Dan Carpenter
Date: Thu Aug 24 2017 - 16:55:50 EST


On Thu, Aug 24, 2017 at 10:47:14PM +0200, Borislav Petkov wrote:
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
> index 59edbe9d4ccb..0179f0fd8a79 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -146,7 +146,7 @@ static bool microcode_matches(struct microcode_header_intel *mc_header,
> return false;
> }
>
> -static struct ucode_patch *__alloc_microcode_buf(void *data, unsigned int size)
> +static struct ucode_patch *memdup_patch(void *data, unsigned int size)
> {
> struct ucode_patch *p;
>
> @@ -183,11 +183,13 @@ static void save_microcode_patch(void *data, unsigned int size)
> if (mc_hdr->rev <= mc_saved_hdr->rev)
> continue;
>
> - p = __alloc_microcode_buf(data, size);
> - if (IS_ERR(p))
> + p = memdup_patch(data, size);
> + if (IS_ERR(p)) {
> pr_err("Error allocating buffer %p\n", data);
> - else
> - list_replace(&iter->plist, &p->plist);
> + continue;
> + }
> +
> + list_replace(&iter->plist, &p->plist);
> }
> }
>

This is just cleanups and doesn't change the behavior.

> @@ -196,11 +198,12 @@ static void save_microcode_patch(void *data, unsigned int size)
> * newly found.
> */
> if (!prev_found) {
> - p = __alloc_microcode_buf(data, size);
> - if (IS_ERR(p))
> + p = memdup_patch(data, size);
> + if (IS_ERR(p)) {
> pr_err("Error allocating buffer for %p\n", data);
> - else
> - list_add_tail(&p->plist, &microcode_cache);
> + return;
> + }
> + list_add_tail(&p->plist, &microcode_cache);
> }

The static checker is still going to complain about the error pointer
from the loop. Perhaps we should only set prev_found if the memdup_patch()
inside the loop succeeds?

regards,
dan carpenter