The LLVM template is first echo-ed into command_out and then
command_out executed. The echo surrounds the template with double
quotes, however, the template itself may contain quotes. This is
generally innocuous but in tools/perf/tests/bpf-script-test-prologue.c
we see:
...
SEC("func=null_lseek file->f_mode offset orig")
...
where the first double quote ends the double quote of the echo, then
the > redirects output into a file called f_mode.
To avoid this inadvertent behavior substitute redirects and similar
characters to be ASCII control codes, then substitute the output in
the echo back again.
Fixes: 5eab5a7ee032 ("perf llvm: Display eBPF compiling command in debug output")
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
tools/perf/util/llvm-utils.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 650ffe336f3a..4e8e243a6e4b 100644
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -531,14 +531,37 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
pr_debug("llvm compiling command template: %s\n", template);
+ /*
+ * Below, substitute control characters for values that can cause the
+ * echo to misbehave, then substitute the values back.
+ */
err = -ENOMEM;
- if (asprintf(&command_echo, "echo -n \"%s\"", template) < 0)
+ if (asprintf(&command_echo, "echo -n \a%s\a", template) < 0)
goto errout;
+#define SWAP_CHAR(a, b) do { if (*p == a) *p = b; } while (0)
+ for (char *p = command_echo; *p; p++) {
+ SWAP_CHAR('<', '\001');
+ SWAP_CHAR('>', '\002');
+ SWAP_CHAR('"', '\003');
+ SWAP_CHAR('\'', '\004');
+ SWAP_CHAR('|', '\005');
+ SWAP_CHAR('&', '\006');
+ SWAP_CHAR('\a', '"');
+ }
err = read_from_pipe(command_echo, (void **) &command_out, NULL);
if (err)
goto errout;
+ for (char *p = command_out; *p; p++) {
+ SWAP_CHAR('\001', '<');
+ SWAP_CHAR('\002', '>');
+ SWAP_CHAR('\003', '"');
+ SWAP_CHAR('\004', '\'');
+ SWAP_CHAR('\005', '|');
+ SWAP_CHAR('\006', '&');
+ }
+#undef SWAP_CHAR
pr_debug("llvm compiling command : %s\n", command_out);
err = read_from_pipe(template, &obj_buf, &obj_buf_sz);
--
2.39.0.314.g84b9a713c41-goog
