[xen staging] xen/gunzip: Allow perform_gunzip() to be called multiple times

[patchbot@xxxxxxx]

commit 33bc2a8495f755510f63629ed3f011134416310c
Author:     Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Wed Mar 3 19:27:56 2021 +0000
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Tue Apr 6 19:30:33 2021 +0100

    xen/gunzip: Allow perform_gunzip() to be called multiple times
    
    Currently perform_gunzip() can only be called once because the
    the internal state (e.g allocate) is not fully re-initialized.
    
    This works fine if you are only booting dom0. But this will break when
    booting multiple using the dom0less that uses compressed kernel images.
    
    This can be resolved by re-initializing bytes_out, malloc_ptr,
    malloc_count every time perform_gunzip() is called.
    
    Note the latter is only re-initialized for hardening purpose as there is
    no guarantee that every malloc() are followed by free() (It should in
    theory!).
    
    Take the opportunity to check the return of alloc_heap_pages() to return
    an error rather than dereferencing a NULL pointer later on failure.
    
    Reported-by: Charles Chiou <cchiou@xxxxxxxxxxxxx>
    Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/gunzip.c  | 5 +++++
 xen/common/inflate.c | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/xen/common/gunzip.c b/xen/common/gunzip.c
index db4efcd34b..425d64e904 100644
--- a/xen/common/gunzip.c
+++ b/xen/common/gunzip.c
@@ -114,11 +114,16 @@ __init int perform_gunzip(char *output, char *image, 
unsigned long image_len)
     window = (unsigned char *)output;
 
     free_mem_ptr = (unsigned long)alloc_xenheap_pages(HEAPORDER, 0);
+    if ( !free_mem_ptr )
+        return -ENOMEM;
+
     free_mem_end_ptr = free_mem_ptr + (PAGE_SIZE << HEAPORDER);
+    init_allocator();
 
     inbuf = (unsigned char *)image;
     insize = image_len;
     inptr = 0;
+    bytes_out = 0;
 
     makecrc();
 
diff --git a/xen/common/inflate.c b/xen/common/inflate.c
index f99c985d61..d8c28a3e95 100644
--- a/xen/common/inflate.c
+++ b/xen/common/inflate.c
@@ -238,6 +238,12 @@ STATIC const ush mask_bits[] = {
 static unsigned long INITDATA malloc_ptr;
 static int INITDATA malloc_count;
 
+static void init_allocator(void)
+{
+    malloc_ptr = free_mem_ptr;
+    malloc_count = 0;
+}
+
 static void *INIT malloc(int size)
 {
     void *p;
--
generated by git-patchbot for /home/xen/git/xen.git#staging