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>

diff --git a/tools/net/bpf_jit_disasm.c b/tools/net/bpf_jit_disasm.c
index c5baf9c591b7bb5a2c280e173f4e0a2b561285fa..618c2bcd4eabc6143b0e7f0431f57b8620101fe5 100644 (file)
--- 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) {