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authorGravatar Samuel Sapalski <samuel.sapalski@nokia.com>2021-03-03 16:31:22 +0100
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2021-03-12 10:45:10 +0100
commitf25d254dfd4243698c31a4f3153d4ac72aa9e9bd (patch)
tree0d4f56adcaf9880ba2189f88a291cefd2ec93117
parentcbfdeba6609b702432886ecf3e2786818a2bc55b (diff)
downloadbusybox-f25d254dfd4243698c31a4f3153d4ac72aa9e9bd.tar.gz
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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 <samuel.sapalski@nokia.com> Signed-off-by: Peter Kaestle <peter.kaestle@nokia.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--archival/libarchive/decompress_gunzip.c12
1 files 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)