busybox: Fix for CVE-2021-42374

An out-of-bounds heap read in unlzma leads to information leak and
denial of service when crafted LZMA-compressed input is decompressed.
This can be triggered by any applet/format that internally supports
LZMA compression.

Reference: https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-42374

(From OE-Core rev: 297719989ebe8ce7d50e3991cba3e268938690ce)

Signed-off-by: Pavel Zhukov <pavel.zhukov@huawei.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 54 insertions, 0 deletions

diff --git a/meta/recipes-core/busybox/busybox/CVE-2021-42374.patch b/meta/recipes-core/busybox/busybox/CVE-2021-42374.patch
new file mode 100644
index 0000000000..aef8a3db85
--- /dev/null
+++ b/meta/recipes-core/busybox/busybox/CVE-2021-42374.patch
@@ -0,0 +1,53 @@
+From 04f052c56ded5ab6a904e3a264a73dc0412b2e78 Mon Sep 17 00:00:00 2001
+From: Denys Vlasenko <vda.linux@googlemail.com>
+Date: Tue, 15 Jun 2021 15:07:57 +0200
+Subject: [PATCH] unlzma: fix a case where we could read before beginning of
+ buffer
+Cc: pavel@zhukoff.net
+
+Testcase:
+
+  21 01 01 00 00 00 00 00 e7 01 01 01 ef 00 df b6
+  00 17 02 10 11 0f ff 00 16 00 00
+
+Unfortunately, the bug is not reliably causing a segfault,
+the behavior depends on what's in memory before the buffer.
+
+function                                             old     new   delta
+unpack_lzma_stream                                  2762    2768      +6
+
+Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
+
+Signed-off-by: Pavel Zhukov <pavel.zhukov@huawei.com>
+
+CVE: CVE-2021-42374
+Upstream-Status: Backport [https://git.busybox.net/busybox/commit/?h=1_33_stable&id=d326be2850ea2bd78fe2c22d6c45c3b861d82937]
+Comment: testdata dropped because of binary format
+
+---
+ archival/libarchive/decompress_unlzma.c |   5 ++++-
+ testsuite/unlzma.tests                  |  17 +++++++++++++----
+ testsuite/unlzma_issue_3.lzma           | Bin 0 -> 27 bytes
+ 3 files changed, 17 insertions(+), 5 deletions(-)
+ create mode 100644 testsuite/unlzma_issue_3.lzma
+
+diff --git a/archival/libarchive/decompress_unlzma.c b/archival/libarchive/decompress_unlzma.c
+index 0744f231a1d64d92676b0cada2342f88f3b39b31..fb5aac8fe9ea0c53e0c2d7a7cbd05a753e39bc9d 100644
+--- a/archival/libarchive/decompress_unlzma.c
++++ b/archival/libarchive/decompress_unlzma.c
+@@ -290,8 +290,11 @@ unpack_lzma_stream(transformer_state_t *xstate)
+                                uint32_t pos;
+ 
+                                pos = buffer_pos - rep0;
+-                               if ((int32_t)pos < 0)
++                               if ((int32_t)pos < 0) {
+                                        pos += header.dict_size;
++                                       if ((int32_t)pos < 0)
++                                               goto bad;
++                               }
+                                match_byte = buffer[pos];
+                                do {
+                                        int bit;
+-- 
+2.34.0
+
diff --git a/meta/recipes-core/busybox/busybox_1.31.1.bb b/meta/recipes-core/busybox/busybox_1.31.1.bb
index d9d5f4f96b..55c00eb483 100644
--- a/meta/recipes-core/busybox/busybox_1.31.1.bb
+++ b/meta/recipes-core/busybox/busybox_1.31.1.bb
@@ -52,6 +52,7 @@ SRC_URI = "https://busybox.net/downloads/busybox-${PV}.tar.bz2;name=tarball \
            file://0001-hwclock-make-glibc-2.31-compatible.patch \
            file://0001-decompress_gunzip-Fix-DoS-if-gzip-is-corrupt.patch \
            file://0001-mktemp-add-tmpdir-option.patch \
+           file://CVE-2021-42374.patch \
            "
 SRC_URI_append_libc-musl = " file://musl.cfg "