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Subject[146/152] x86/microcode: Fix double vfree() and remove redundant pointer checks before vfree()
2.6.36-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jesper Juhl <jj@chaosbits.net>

commit 5cdd2de0a76d0ac47f107c8a7b32d75d25768dc1 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86/kernel/microcode_intel.c | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)

--- a/arch/x86/kernel/microcode_intel.c
+++ b/arch/x86/kernel/microcode_intel.c
@@ -364,8 +364,7 @@ static enum ucode_state generic_load_mic

/* 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_mic

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_mic
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_mic
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",



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