[Xen-changelog] [xen master] x86/microcode: Avoid undefined behaviour from signed integer overflow

[patchbot@xxxxxxx]

commit e64f22df3c1a0b70031ad6e8c0fc875d27cc5c3c
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Aug 5 14:26:21 2016 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Aug 11 10:09:21 2016 +0100

    x86/microcode: Avoid undefined behaviour from signed integer overflow
    
    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@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 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");
--
generated by git-patchbot for /home/xen/git/xen.git#master

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog