Am 25.08.2017 12:04, schrieb Borislav Petkov:
> From: Borislav Petkov <[email protected]>
>
> Avoid potentially dereferencing a NULL pointer when saving a microcode
> patch for early loading on the application processors.
>
> While at it, drop the IS_ERR() checking in favor of simpler, NULL-ptr
> checks which are sufficient and rename __alloc_microcode_buf() to
> memdup_patch() to more precisely denote what it does.
>
> No functionality change.
>
> Reported-by: Dan Carpenter <[email protected]>
> Signed-off-by: Borislav Petkov <[email protected]>
> ---
> arch/x86/kernel/cpu/microcode/intel.c | 27 ++++++++++++++-------------
> 1 file changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c
> b/arch/x86/kernel/cpu/microcode/intel.c
> index 59edbe9d4ccb..8f7a9bbad514 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -146,18 +146,18 @@ 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;
>
> p = kzalloc(sizeof(struct ucode_patch), GFP_KERNEL);
> if (!p)
> - return ERR_PTR(-ENOMEM);
> + return NULL;
>
> p->data = kmemdup(data, size, GFP_KERNEL);
> if (!p->data) {
> kfree(p);
> - return ERR_PTR(-ENOMEM);
> + return NULL;
> }
>
> return p;
> @@ -183,8 +183,8 @@ 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 (!p)
> pr_err("Error allocating buffer %p\n", data);
> else
> list_replace(&iter->plist, &p->plist);
> @@ -196,24 +196,25 @@ 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 (!p)
> pr_err("Error allocating buffer for %p\n", data);
> else
> list_add_tail(&p->plist, µcode_cache);
> }
>
> + if (!p)
> + return;
> +
just a bit nitpicking,
i would expect something like that:
p = memdup_patch(data, size);
if (!p) {
pr_err("Error allocating buffer for %p\n", data);
return;
}
list_add_tail(&p->plist, µcode_cache);
... because this is a normal pattern for OOF conditions and
everyone will ask "Why continue when there is no memory"
just my 2 cents
re,
wh
> /*
> * Save for early loading. On 32-bit, that needs to be a physical
> * address as the APs are running from physical addresses, before
> * paging has been enabled.
> */
> - if (p) {
> - if (IS_ENABLED(CONFIG_X86_32))
> - intel_ucode_patch = (struct microcode_intel
> *)__pa_nodebug(p->data);
> - else
> - intel_ucode_patch = p->data;
> - }
> + if (IS_ENABLED(CONFIG_X86_32))
> + intel_ucode_patch = (struct microcode_intel
> *)__pa_nodebug(p->data);
> + else
> + intel_ucode_patch = p->data;
> }
>
> static int microcode_sanity_check(void *mc, int print_err)
