From 77cccc74deede443e8b9102299efc869a52b65b2 Mon Sep 17 00:00:00 2001 From: Ilya Maximets Date: Tue, 16 Feb 2021 23:27:30 +0100 Subject: [PATCH] ofp-actions: Fix use-after-free while decoding RAW_ENCAP. While decoding RAW_ENCAP action, decode_ed_prop() might re-allocate ofpbuf if there is no enough space left. However, function 'decode_NXAST_RAW_ENCAP' continues to use old pointer to 'encap' structure leading to write-after-free and incorrect decoding. ==3549105==ERROR: AddressSanitizer: heap-use-after-free on address 0x60600000011a at pc 0x0000005f6cc6 bp 0x7ffc3a2d4410 sp 0x7ffc3a2d4408 WRITE of size 2 at 0x60600000011a thread T0 #0 0x5f6cc5 in decode_NXAST_RAW_ENCAP lib/ofp-actions.c:4461:20 #1 0x5f0551 in ofpact_decode ./lib/ofp-actions.inc2:4777:16 #2 0x5ed17c in ofpacts_decode lib/ofp-actions.c:7752:21 #3 0x5eba9a in ofpacts_pull_openflow_actions__ lib/ofp-actions.c:7791:13 #4 0x5eb9fc in ofpacts_pull_openflow_actions lib/ofp-actions.c:7835:12 #5 0x64bb8b in ofputil_decode_packet_out lib/ofp-packet.c:1113:17 #6 0x65b6f4 in ofp_print_packet_out lib/ofp-print.c:148:13 #7 0x659e3f in ofp_to_string__ lib/ofp-print.c:1029:16 #8 0x659b24 in ofp_to_string lib/ofp-print.c:1244:21 #9 0x65a28c in ofp_print lib/ofp-print.c:1288:28 #10 0x540d11 in ofctl_ofp_parse utilities/ovs-ofctl.c:2814:9 #11 0x564228 in ovs_cmdl_run_command__ lib/command-line.c:247:17 #12 0x56408a in ovs_cmdl_run_command lib/command-line.c:278:5 #13 0x5391ae in main utilities/ovs-ofctl.c:179:9 #14 0x7f6911ce9081 in __libc_start_main (/lib64/libc.so.6+0x27081) #15 0x461fed in _start (utilities/ovs-ofctl+0x461fed) Fix that by getting a new pointer before using. Credit to OSS-Fuzz. Fuzzer regression test will fail only with AddressSanitizer enabled. Upstream-status: Backport Reported-at: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27851 Fixes: f839892a206a ("OF support and translation of generic encap and decap") Acked-by: William Tu Signed-off-by: Ilya Maximets --- lib/ofp-actions.c | 2 ++ tests/automake.mk | 3 ++- tests/fuzz-regression-list.at | 1 + tests/fuzz-regression/ofp_print_fuzzer-6540965472632832 | 0 4 files changed, 5 insertions(+), 1 deletion(-) create mode 100644 tests/fuzz-regression/ofp_print_fuzzer-6540965472632832 diff --git a/lib/ofp-actions.c b/lib/ofp-actions.c index e2e829772..0342a228b 100644 --- a/lib/ofp-actions.c +++ b/lib/ofp-actions.c @@ -4431,6 +4431,7 @@ decode_NXAST_RAW_ENCAP(const struct nx_action_encap *nae, { struct ofpact_encap *encap; const struct ofp_ed_prop_header *ofp_prop; + const size_t encap_ofs = out->size; size_t props_len; uint16_t n_props = 0; int err; @@ -4458,6 +4459,7 @@ decode_NXAST_RAW_ENCAP(const struct nx_action_encap *nae, } n_props++; } + encap = ofpbuf_at_assert(out, encap_ofs, sizeof *encap); encap->n_props = n_props; out->header = &encap->ofpact; ofpact_finish_ENCAP(out, &encap); diff --git a/tests/automake.mk b/tests/automake.mk index 677b99a6b..fc80e027d 100644 --- a/tests/automake.mk +++ b/tests/automake.mk @@ -134,7 +134,8 @@ FUZZ_REGRESSION_TESTS = \ tests/fuzz-regression/ofp_print_fuzzer-5722747668791296 \ tests/fuzz-regression/ofp_print_fuzzer-6285128790704128 \ tests/fuzz-regression/ofp_print_fuzzer-6470117922701312 \ - tests/fuzz-regression/ofp_print_fuzzer-6502620041576448 + tests/fuzz-regression/ofp_print_fuzzer-6502620041576448 \ + tests/fuzz-regression/ofp_print_fuzzer-6540965472632832 $(srcdir)/tests/fuzz-regression-list.at: tests/automake.mk $(AM_V_GEN)for name in $(FUZZ_REGRESSION_TESTS); do \ basename=`echo $$name | sed 's,^.*/,,'`; \ diff --git a/tests/fuzz-regression-list.at b/tests/fuzz-regression-list.at index e3173fb88..2347c690e 100644 --- a/tests/fuzz-regression-list.at +++ b/tests/fuzz-regression-list.at @@ -21,3 +21,4 @@ TEST_FUZZ_REGRESSION([ofp_print_fuzzer-5722747668791296]) TEST_FUZZ_REGRESSION([ofp_print_fuzzer-6285128790704128]) TEST_FUZZ_REGRESSION([ofp_print_fuzzer-6470117922701312]) TEST_FUZZ_REGRESSION([ofp_print_fuzzer-6502620041576448]) +TEST_FUZZ_REGRESSION([ofp_print_fuzzer-6540965472632832]) diff --git a/tests/fuzz-regression/ofp_print_fuzzer-6540965472632832 b/tests/fuzz-regression/ofp_print_fuzzer-6540965472632832 new file mode 100644 index 000000000..e69de29bb -- 2.17.1