From fe791386ebc270219ca00406c9fdadc5130b64ee Mon Sep 17 00:00:00 2001 From: Samuel Sapalski Date: Wed, 3 Mar 2021 16:31:22 +0100 Subject: [PATCH] decompress_gunzip: Fix DoS if gzip is corrupt 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 Signed-off-by: Peter Kaestle Signed-off-by: Denys Vlasenko Upstream-Status: Backport CVE: CVE-2021-28831 Signed-off-by: Chen Qi --- archival/libarchive/decompress_gunzip.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/archival/libarchive/decompress_gunzip.c b/archival/libarchive/decompress_gunzip.c index eb3b64930..e93cd5005 100644 --- a/archival/libarchive/decompress_gunzip.c +++ b/archival/libarchive/decompress_gunzip.c @@ -220,10 +220,20 @@ static const uint8_t border[] ALIGN1 = { * each table. * 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) { 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. */ while (p) { 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 * 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, const unsigned s, const struct cp_ext *cp_ext, unsigned *m)