From: Andrii Nakryiko andrii@kernel.org
[ Upstream commit eceae70bdeaeb6b8ceb662983cf663ff352fbc96 ]
strncat()'s third argument is how many bytes will be added *in addition* to already existing bytes in destination. Plus extra zero byte will be added after that. So existing use in test_sockmap has many opportunities to overflow the string and cause memory corruptions. And in this case, GCC complains for a good reason.
Fixes: 16962b2404ac ("bpf: sockmap, add selftests") Fixes: 73563aa3d977 ("selftests/bpf: test_sockmap, print additional test options") Fixes: 1ade9abadfca ("bpf: test_sockmap, add options for msg_pop_data() helper") Fixes: 463bac5f1ca7 ("bpf, selftests: Add test for ktls with skb bpf ingress policy") Fixes: e9dd904708c4 ("bpf: add tls support for testing in test_sockmap") Fixes: 753fb2ee0934 ("bpf: sockmap, add msg_peek tests to test_sockmap") Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Link: https://lore.kernel.org/bpf/20201203235440.2302137-2-andrii@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/testing/selftests/bpf/test_sockmap.c | 36 ++++++++++++++-------- 1 file changed, 23 insertions(+), 13 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_sockmap.c b/tools/testing/selftests/bpf/test_sockmap.c index 0fa1e421c3d7a..427ca00a32177 100644 --- a/tools/testing/selftests/bpf/test_sockmap.c +++ b/tools/testing/selftests/bpf/test_sockmap.c @@ -1273,6 +1273,16 @@ static char *test_to_str(int test) return "unknown"; }
+static void append_str(char *dst, const char *src, size_t dst_cap) +{ + size_t avail = dst_cap - strlen(dst); + + if (avail <= 1) /* just zero byte could be written */ + return; + + strncat(dst, src, avail - 1); /* strncat() adds + 1 for zero byte */ +} + #define OPTSTRING 60 static void test_options(char *options) { @@ -1281,42 +1291,42 @@ static void test_options(char *options) memset(options, 0, OPTSTRING);
if (txmsg_pass) - strncat(options, "pass,", OPTSTRING); + append_str(options, "pass,", OPTSTRING); if (txmsg_redir) - strncat(options, "redir,", OPTSTRING); + append_str(options, "redir,", OPTSTRING); if (txmsg_drop) - strncat(options, "drop,", OPTSTRING); + append_str(options, "drop,", OPTSTRING); if (txmsg_apply) { snprintf(tstr, OPTSTRING, "apply %d,", txmsg_apply); - strncat(options, tstr, OPTSTRING); + append_str(options, tstr, OPTSTRING); } if (txmsg_cork) { snprintf(tstr, OPTSTRING, "cork %d,", txmsg_cork); - strncat(options, tstr, OPTSTRING); + append_str(options, tstr, OPTSTRING); } if (txmsg_start) { snprintf(tstr, OPTSTRING, "start %d,", txmsg_start); - strncat(options, tstr, OPTSTRING); + append_str(options, tstr, OPTSTRING); } if (txmsg_end) { snprintf(tstr, OPTSTRING, "end %d,", txmsg_end); - strncat(options, tstr, OPTSTRING); + append_str(options, tstr, OPTSTRING); } if (txmsg_start_pop) { snprintf(tstr, OPTSTRING, "pop (%d,%d),", txmsg_start_pop, txmsg_start_pop + txmsg_pop); - strncat(options, tstr, OPTSTRING); + append_str(options, tstr, OPTSTRING); } if (txmsg_ingress) - strncat(options, "ingress,", OPTSTRING); + append_str(options, "ingress,", OPTSTRING); if (txmsg_redir_skb) - strncat(options, "redir_skb,", OPTSTRING); + append_str(options, "redir_skb,", OPTSTRING); if (txmsg_ktls_skb) - strncat(options, "ktls_skb,", OPTSTRING); + append_str(options, "ktls_skb,", OPTSTRING); if (ktls) - strncat(options, "ktls,", OPTSTRING); + append_str(options, "ktls,", OPTSTRING); if (peek_flag) - strncat(options, "peek,", OPTSTRING); + append_str(options, "peek,", OPTSTRING); }
static int __test_exec(int cgrp, int test, struct sockmap_options *opt)