File 5e3bd3f8-xmalloc-guard-against-overflow.patch of Package xen.14764

# Commit cf38b4926e2b55d1d7715cff5095a7444f5ed42d
# Date 2020-02-06 09:53:12 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
xmalloc: guard against integer overflow

There are hypercall handling paths (EFI ones are what this was found
with) needing to allocate buffers of a caller specified size. This is
generally fine, as our page allocator enforces an upper bound on all
allocations. However, certain extremely large sizes could, when adding
in allocator overhead, result in an apparently tiny allocation size,
which would typically result in either a successful allocation, but a
severe buffer overrun when using that memory block, or in a crash right
in the allocator code.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>

--- a/xen/common/xmalloc_tlsf.c
+++ b/xen/common/xmalloc_tlsf.c
@@ -388,7 +388,17 @@ void *xmem_pool_alloc(unsigned long size
         pool->init_region = region;
     }
 
-    size = (size < MIN_BLOCK_SIZE) ? MIN_BLOCK_SIZE : ROUNDUP_SIZE(size);
+    if ( size < MIN_BLOCK_SIZE )
+        size = MIN_BLOCK_SIZE;
+    else
+    {
+        tmp_size = ROUNDUP_SIZE(size);
+        /* Guard against overflow. */
+        if ( tmp_size < size )
+            return NULL;
+        size = tmp_size;
+    }
+
     /* Rounding up the requested size and calculating fl and sl */
 
     spin_lock(&pool->lock);
@@ -583,6 +593,10 @@ void *_xmalloc(unsigned long size, unsig
         align = MEM_ALIGN;
     size += align - MEM_ALIGN;
 
+    /* Guard against overflow. */
+    if ( size < align - MEM_ALIGN )
+        return NULL;
+
     if ( !xenpool )
         tlsf_init();