[PATCH v3 4/7] trace2: remove use of ALLOC_ARRAY()

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <stolee@gmail.com>

The banned-die.h header is used to prevent use of helper methods that
call die(). Remove use of the ALLOC_ARRAY() helper, which calls die() on
allocation failures. Replace the use in trace2.c with a more direct
allocation and soft failure when allocation fails. This prevents die()
recursion loops when memory allocation fails and trace2 logs are
enabled.

The tricky part about this change is how to handle the results from
redact_arg(), which is a 'const char *' result because it might be a
pointer directly to the externally-controlled argument. When it is
different from the argument, then it is indeed a newly-allocated string
that we need to free before returning. This requires using a (char *)
cast to allow a change.

Signed-off-by: Derrick Stolee <stolee@gmail.com>
---
 banned-die.h |  3 +++
 trace2.c     | 16 ++++++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/banned-die.h b/banned-die.h
index bf16ec5ba9..0ad9a6c492 100644
--- a/banned-die.h
+++ b/banned-die.h
@@ -17,4 +17,7 @@
 #undef xstrdup
 #define xstrdup(str) BANNED(xstrdup)
 
+#undef ALLOC_ARRAY
+#define ALLOC_ARRAY(x, alloc) BANNED(ALLOC_ARRAY)
+
 #endif /* BANNED_DIE_H */
diff --git a/trace2.c b/trace2.c
index 8c974dee87..ea021c602e 100644
--- a/trace2.c
+++ b/trace2.c
@@ -305,7 +305,11 @@ static const char **redact_argv(const char **argv)
 	for (j = 0; argv[j]; j++)
 		; /* keep counting */
 
-	ALLOC_ARRAY(ret, j + 1);
+	ret = calloc(j + 1, sizeof(*ret));
+	if (!ret) {
+		free((char *)redacted);
+		return NULL;
+	}
 	ret[j] = NULL;
 
 	for (j = 0; j < i; j++)
@@ -346,6 +350,8 @@ void trace2_cmd_start_fl(const char *file, int line, const char **argv)
 	us_elapsed_absolute = tr2tls_absolute_elapsed(us_now);
 
 	redacted = redact_argv(argv);
+	if (!redacted)
+		return;
 
 	for_each_wanted_builtin (j, tgt_j)
 		if (tgt_j->pfn_start_fl)
@@ -514,6 +520,7 @@ void trace2_child_start_fl(const char *file, int line,
 	uint64_t us_now;
 	uint64_t us_elapsed_absolute;
 	const char **orig_argv = cmd->args.v;
+	const char **redacted;
 
 	if (!trace2_enabled)
 		return;
@@ -531,7 +538,10 @@ void trace2_child_start_fl(const char *file, int line,
 	 * temporarily replace the original argv (inside the `strvec`)
 	 * with a possibly redacted version.
 	 */
-	cmd->args.v = redact_argv(orig_argv);
+	redacted = redact_argv(orig_argv);
+	if (!redacted)
+		return;
+	cmd->args.v = redacted;
 
 	for_each_wanted_builtin (j, tgt_j)
 		if (tgt_j->pfn_child_start_fl)
@@ -623,6 +633,8 @@ int trace2_exec_fl(const char *file, int line, const char *exe,
 	exec_id = tr2tls_locked_increment(&tr2_next_exec_id);
 
 	redacted = redact_argv(argv);
+	if (!redacted)
+		return exec_id;
 
 	for_each_wanted_builtin (j, tgt_j)
 		if (tgt_j->pfn_exec_fl)
-- 
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