x86/microcode: Fix double vfree() and remove redundant pointer checks before vfree()

In arch/x86/kernel/microcode_intel.c::generic_load_microcode()
we have  this:

	while (leftover) {
		...
		if (get_ucode_data(mc, ucode_ptr, mc_size) ||
		    microcode_sanity_check(mc) < 0) {
			vfree(mc);
			break;
		}
		...
	}

	if (mc)
		vfree(mc);

This will cause a double free of 'mc'. This patch fixes that by
just  removing the vfree() call in the loop since 'mc' will be
freed nicely just  after we break out of the loop.

There's also a second change in the patch. I noticed a lot of
checks for  pointers being NULL before passing them to vfree().
That's completely  redundant since vfree() deals gracefully with
being passed a NULL pointer.  Removing the redundant checks
yields a nice size decrease for the object  file.

Size before the patch:
   text    data     bss     dec     hex filename
   4578     240    1032    5850    16da arch/x86/kernel/microcode_intel.o
Size after the patch:
   text    data     bss     dec     hex filename
   4489     240     984    5713    1651 arch/x86/kernel/microcode_intel.o

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: Tigran Aivazian <tigran@aivazian.fsnet.co.uk>
Cc: Shaohua Li <shaohua.li@intel.com>
LKML-Reference: <alpine.LNX.2.00.1012251946100.10759@swampdragon.chaosbits.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 11 deletions

diff --git a/arch/x86/kernel/microcode_intel.c b/arch/x86/kernel/microcode_intel.c
index dcb65cc0a053..1a1b606d3e92 100644
--- a/arch/x86/kernel/microcode_intel.c
+++ b/arch/x86/kernel/microcode_intel.c
@@ -364,8 +364,7 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
 
                 /* For performance reasons, reuse mc area when possible */
                 if (!mc || mc_size > curr_mc_size) {
-                        if (mc)
-                                vfree(mc);
+                        vfree(mc);
                         mc = vmalloc(mc_size);
                         if (!mc)
                                 break;
@@ -374,13 +373,11 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
 
                 if (get_ucode_data(mc, ucode_ptr, mc_size) ||
                     microcode_sanity_check(mc) < 0) {
-                        vfree(mc);
                         break;
                 }
 
                 if (get_matching_microcode(&uci->cpu_sig, mc, new_rev)) {
-                        if (new_mc)
-                                vfree(new_mc);
+                        vfree(new_mc);
                         new_rev = mc_header.rev;
                         new_mc  = mc;
                         mc = NULL;      /* trigger new vmalloc */
@@ -390,12 +387,10 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
                 leftover  -= mc_size;
         }
 
-        if (mc)
-                vfree(mc);
+        vfree(mc);
 
         if (leftover) {
-                if (new_mc)
-                        vfree(new_mc);
+                vfree(new_mc);
                 state = UCODE_ERROR;
                 goto out;
         }
@@ -405,8 +400,7 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
                 goto out;
         }
 
-        if (uci->mc)
-                vfree(uci->mc);
+        vfree(uci->mc);
         uci->mc = (struct microcode_intel *)new_mc;
 
         pr_debug("CPU%d found a matching microcode update with version 0x%x (current=0x%x)\n",