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decompress_gunzip: Fix DoS if gzip is corrupt

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On certain corrupt gzip files, huft_build will set the error bit on
the result pointer. If afterwards abort_unzip is called huft_free
might run into a segmentation fault or an invalid pointer to
free(p).

In order to mitigate this, we check in huft_free if the error bit
is set and clear it before the linked list is freed.

Signed-off-by: Samuel Sapalski <samuel.sapalski@nokia.com>
Signed-off-by: Peter Kaestle <peter.kaestle@nokia.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Samuel Sapalski 2021-03-03 16:31:22 +01:00 committed by Denys Vlasenko
parent cbfdeba660
commit f25d254dfd
1 changed files with 10 additions and 2 deletions
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12
archival/libarchive/decompress_gunzip.c
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@ -220,10 +220,20 @@ static const uint8_t border[] ALIGN1 = {
* each table. * each table.
* t: table to free * t: table to free
*/ */
#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
#define ERR_RET ((huft_t*)(uintptr_t)1)
static void huft_free(huft_t *p) static void huft_free(huft_t *p)
{ {
huft_t *q; huft_t *q;
/*
* If 'p' has the error bit set we have to clear it, otherwise we might run
* into a segmentation fault or an invalid pointer to free(p)
*/
if (BAD_HUFT(p)) {
p = (huft_t*)((uintptr_t)(p) ^ (uintptr_t)(ERR_RET));
}
/* Go through linked list, freeing from the malloced (t[-1]) address. */ /* Go through linked list, freeing from the malloced (t[-1]) address. */
while (p) { while (p) {
q = (--p)->v.t; q = (--p)->v.t;
@ -289,8 +299,6 @@ static unsigned fill_bitbuffer(STATE_PARAM unsigned bitbuffer, unsigned *current
* or a valid pointer to a Huffman table, ORed with 0x1 if incompete table * or a valid pointer to a Huffman table, ORed with 0x1 if incompete table
* is given: "fixed inflate" decoder feeds us such data. * is given: "fixed inflate" decoder feeds us such data.
*/ */
#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
#define ERR_RET ((huft_t*)(uintptr_t)1)
static huft_t* huft_build(const unsigned *b, const unsigned n, static huft_t* huft_build(const unsigned *b, const unsigned n,
const unsigned s, const struct cp_ext *cp_ext, const unsigned s, const struct cp_ext *cp_ext,
unsigned *m) unsigned *m)