From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xen.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Kevin Tian <kevin.tian@intel.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Jan Beulich <JBeulich@suse.com>
Subject: [PATCH] x86/microcode: Avoid undefined behaviour from signed integer overflow
Date: Tue, 9 Aug 2016 13:48:04 +0100 [thread overview]
Message-ID: <1470746884-27118-3-git-send-email-andrew.cooper3@citrix.com> (raw)
In-Reply-To: <1470746884-27118-1-git-send-email-andrew.cooper3@citrix.com>
The checksums should be calculated using unsigned 32bit integers, as they are
intended to overflow and end at 0. Replace some other signed integers with
unsigned ones, to avoid mixed-sign comparisons.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Kevin Tian <kevin.tian@intel.com>
CC: Jun Nakajima <jun.nakajima@intel.com>
v2:
* Include the extended checksum
* Swap more integers to being unsigned
---
xen/arch/x86/microcode_intel.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/xen/arch/x86/microcode_intel.c b/xen/arch/x86/microcode_intel.c
index 6949c25..93d9d0f 100644
--- a/xen/arch/x86/microcode_intel.c
+++ b/xen/arch/x86/microcode_intel.c
@@ -143,7 +143,8 @@ static int microcode_sanity_check(void *mc)
struct extended_sigtable *ext_header = NULL;
struct extended_signature *ext_sig;
unsigned long total_size, data_size, ext_table_size;
- int sum, orig_sum, ext_sigcount = 0, i;
+ unsigned int ext_sigcount = 0, i;
+ uint32_t sum, orig_sum;
total_size = get_totalsize(mc_header);
data_size = get_datasize(mc_header);
@@ -183,8 +184,8 @@ static int microcode_sanity_check(void *mc)
/* check extended table checksum */
if ( ext_table_size )
{
- int ext_table_sum = 0;
- int *ext_tablep = (int *)ext_header;
+ uint32_t ext_table_sum = 0;
+ uint32_t *ext_tablep = (uint32_t *)ext_header;
i = ext_table_size / DWSIZE;
while ( i-- )
@@ -201,7 +202,7 @@ static int microcode_sanity_check(void *mc)
orig_sum = 0;
i = (MC_HEADER_SIZE + data_size) / DWSIZE;
while ( i-- )
- orig_sum += ((int *)mc)[i];
+ orig_sum += ((uint32_t *)mc)[i];
if ( orig_sum )
{
printk(KERN_ERR "microcode: aborting, bad checksum\n");
--
2.1.4
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next prev parent reply other threads:[~2016-08-09 12:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-05 13:50 [PATCH 1/3] xen/common: Avoid undefined behaviour by shifting into a sign bit Andrew Cooper
2016-08-05 13:50 ` [PATCH 2/3] xen/x86: " Andrew Cooper
2016-08-05 14:06 ` Jan Beulich
2016-08-05 13:50 ` [PATCH 3/3] x86/microcode: Avoid undefined behaviour from signed integer overflow Andrew Cooper
2016-08-05 14:09 ` Jan Beulich
2016-08-11 8:42 ` Tian, Kevin
2016-08-05 14:04 ` [PATCH 1/3] xen/common: Avoid undefined behaviour by shifting into a sign bit Jan Beulich
2016-08-05 14:07 ` George Dunlap
2016-08-09 12:48 ` [PATCH] " Andrew Cooper
2016-08-09 12:48 ` [PATCH] xen/x86: " Andrew Cooper
2016-08-09 12:48 ` Andrew Cooper [this message]
2016-08-09 14:00 ` [PATCH] xen/common: " Jan Beulich
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