[Xen-devel] [PATCH 7/9] Decompressors: validate match distance in unlzma.c

["Jan Beulich" <JBeulich@xxxxxxxx>]

From: Lasse Collin <lasse.collin@xxxxxxxxxxx>

Validate the newly decoded distance (rep0) in process_bit1().  This is to
detect corrupt LZMA data quickly.  The old code can run for long time
producing garbage until it hits the end of the input.

Signed-off-by: Lasse Collin <lasse.collin@xxxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/unlzma.c
+++ b/xen/common/unlzma.c
@@ -516,6 +516,9 @@ static inline int INIT process_bit1(stru
                        cst->rep0 = pos_slot;
                if (++(cst->rep0) == 0)
                        return 0;
+               if (cst->rep0 > wr->header->dict_size
+                               || cst->rep0 > get_pos(wr))
+                       return -1;
        }
 
        len += LZMA_MATCH_MIN_LEN;

Attachment: unlzma-validate-match-distance.patch
Description: Text document

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