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x86/microcode/intel: Improve microcode patches saving flow 

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 <dan.carpenter@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-janitors@vger.kernel.org
Link: http://lkml.kernel.org/r/20170825100456.n236w3jebteokfd6@pd.tnic
This commit is contained in:
Borislav Petkov 2017-08-25 12:04:56 +02:00 committed by Thomas Gleixner
parent 0e3258753f
commit aa78c1ccfa
1 changed files with 14 additions and 13 deletions
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27
arch/x86/kernel/cpu/microcode/intel.c
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@ -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, &microcode_cache);
}
if (!p)
return;
/*
* 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)