unzip: test for bad archive SEGVing

function                                             old     new   delta
huft_build                                          1296    1300      +4

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
(cherry picked from commit 1de25a6e87e0e627aa34298105a3d17c60a1f44e)
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/archival/libarchive/decompress_gunzip.c b/archival/libarchive/decompress_gunzip.c
index 1360abef7..c76fd31da 100644
--- a/archival/libarchive/decompress_gunzip.c
+++ b/archival/libarchive/decompress_gunzip.c
@@ -305,11 +305,12 @@ static int huft_build(const unsigned *b, const unsigned n,
         unsigned i;             /* counter, current code */
         unsigned j;             /* counter */
         int k;                  /* number of bits in current code */
-        unsigned *p;            /* pointer into c[], b[], or v[] */
+        const unsigned *p;      /* pointer into c[], b[], or v[] */
         huft_t *q;              /* points to current table */
         huft_t r;               /* table entry for structure assignment */
         huft_t *u[BMAX];        /* table stack */
         unsigned v[N_MAX];      /* values in order of bit length */
+        unsigned v_end;
         int ws[BMAX + 1];       /* bits decoded stack */
         int w;                  /* bits decoded */
         unsigned x[BMAX + 1];   /* bit offsets, then code stack */
@@ -324,7 +325,7 @@ static int huft_build(const unsigned *b, const unsigned n,
 
         /* Generate counts for each bit length */
         memset(c, 0, sizeof(c));
-        p = (unsigned *) b; /* cast allows us to reuse p for pointing to b */
+        p = b;
         i = n;
         do {
                 c[*p]++; /* assume all entries <= BMAX */
@@ -365,12 +366,14 @@ static int huft_build(const unsigned *b, const unsigned n,
         }
 
         /* Make a table of values in order of bit lengths */
-        p = (unsigned *) b;
+        p = b;
         i = 0;
+        v_end = 0;
         do {
                 j = *p++;
                 if (j != 0) {
                         v[x[j]++] = i;
+                        v_end = x[j];
                 }
         } while (++i < n);
 
@@ -432,7 +435,7 @@ static int huft_build(const unsigned *b, const unsigned n,
 
                         /* set up table entry in r */
                         r.b = (unsigned char) (k - w);
-                        if (p >= v + n) {
+                        if (p >= v + v_end) { // Was "if (p >= v + n)" but v[] can be shorter!
                                 r.e = 99; /* out of values--invalid code */
                         } else if (*p < s) {
                                 r.e = (unsigned char) (*p < 256 ? 16 : 15);     /* 256 is EOB code */