tools: bpf_jit_disasm: fix segfault on disabled debugging log output

With recent debugging, I noticed that bpf_jit_disasm segfaults when
there's no debugging output from the JIT compiler to the kernel log.

Reason is that when regexec(3) doesn't match on anything, start/end
offsets are not being filled out and contain some uninitialized garbage
from stack. Thus, we need zero out offsets first.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/tools/net/bpf_jit_disasm.c b/tools/net/bpf_jit_disasm.c
index c5baf9c591b7..618c2bcd4eab 100644
--- a/tools/net/bpf_jit_disasm.c
+++ b/tools/net/bpf_jit_disasm.c
@@ -123,6 +123,8 @@ static int get_last_jit_image(char *haystack, size_t hlen,
         assert(ret == 0);
 
         ptr = haystack;
+        memset(pmatch, 0, sizeof(pmatch));
+
         while (1) {
                 ret = regexec(&regex, ptr, 1, pmatch, 0);
                 if (ret == 0) {