[Xen-changelog] [xen-unstable] Decompressors: validate match distance in unlzma.c

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Lasse Collin <lasse.collin@xxxxxxxxxxx>
# Date 1321018464 -3600
# Node ID 88347644935e4de008e16daa13d10d11b0e726d3
# Parent  2ffeeb28e9be98c932905f7fd2bf80bfc089622c
Decompressors: validate match distance in unlzma.c

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>
Acked-by: Keir Fraser <keir@xxxxxxx>
Committed-by: Jan Beulich <jbeulich@xxxxxxxx>
---


diff -r 2ffeeb28e9be -r 88347644935e xen/common/unlzma.c
--- a/xen/common/unlzma.c       Fri Nov 11 14:33:30 2011 +0100
+++ b/xen/common/unlzma.c       Fri Nov 11 14:34:24 2011 +0100
@@ -516,6 +516,9 @@
                        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;

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