[PATCH net] tools: bpf_jit_disasm: fix segfault on disabled debugging log output

[Daniel Borkmann]

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 <dan...@iogearbox.net>
---
 tools/net/bpf_jit_disasm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/net/bpf_jit_disasm.c b/tools/net/bpf_jit_disasm.c
index c5baf9c..618c2bc 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) {
-- 
1.9.3

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