[PATCH 1/6] run_external_diff: use an argv_array for the command line
We currently generate the command-line for the external command using a fixed-length array of size 10. But if there is a rename, we actually need 11 elements (10 items, plus a NULL), and end up writing a random NULL onto the stack.
Rather than bump the limit, let's just an argv_array, which makes this sort of error impossible.
Noticed-by: Max L <infthi.inbox@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
---
This was actually noticed by a GitHub user, who proposed bumping
the array size to 11:
https://github.com/git/git/pull/92
Even though this fix is a bigger change, I'd rather do it this way, as it is more obviously correct to a reader (and it solves the problem forever). I pulled the name/email from that commit, but please let me know if you'd prefer to be credited differently.
diff.c | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)
Show changes to diff.c +16 −16
diff --git a/diff.c b/diff.c
index 539997f..b154284 100644
--- a/diff.c
+++ b/diff.c
@@ -16,6 +16,7 @@
#include "submodule.h"
#include "ll-merge.h"
#include "string-list.h"
+#include "argv-array.h"
#ifdef NO_FAST_WORKING_DIRECTORY
#define FAST_WORKING_DIRECTORY 0
@@ -2902,9 +2903,8 @@ static void run_external_diff(const char *pgm,
int complete_rewrite,
struct diff_options *o)
{
- const char *spawn_arg[10];
+ struct argv_array argv = ARGV_ARRAY_INIT;
int retval;
- const char **arg = &spawn_arg[0];
struct diff_queue_struct *q = &diff_queued_diff;
const char *env[3] = { NULL };
char env_counter[50];
@@ -2915,23 +2915,22 @@ static void run_external_diff(const char *pgm,
const char *othername = (other ? other : name);
temp_one = prepare_temp_file(name, one);
temp_two = prepare_temp_file(othername, two);
- *arg++ = pgm;
- *arg++ = name;
- *arg++ = temp_one->name;
- *arg++ = temp_one->hex;
- *arg++ = temp_one->mode;
- *arg++ = temp_two->name;
- *arg++ = temp_two->hex;
- *arg++ = temp_two->mode;
+ argv_array_push(&argv, pgm);
+ argv_array_push(&argv, name);
+ argv_array_push(&argv, temp_one->name);
+ argv_array_push(&argv, temp_one->hex);
+ argv_array_push(&argv, temp_one->mode);
+ argv_array_push(&argv, temp_two->name);
+ argv_array_push(&argv, temp_two->hex);
+ argv_array_push(&argv, temp_two->mode);
if (other) {
- *arg++ = other;
- *arg++ = xfrm_msg;
+ argv_array_push(&argv, other);
+ argv_array_push(&argv, xfrm_msg);
}
} else {
- *arg++ = pgm;
- *arg++ = name;
+ argv_array_push(&argv, pgm);
+ argv_array_push(&argv, name);
}
- *arg = NULL;
fflush(NULL);
env[0] = env_counter;
@@ -2940,8 +2939,9 @@ static void run_external_diff(const char *pgm,
env[1] = env_total;
snprintf(env_total, sizeof(env_total), "GIT_DIFF_PATH_TOTAL=%d", q->nr);
- retval = run_command_v_opt_cd_env(spawn_arg, RUN_USING_SHELL, NULL, env);
+ retval = run_command_v_opt_cd_env(argv.argv, RUN_USING_SHELL, NULL, env);
remove_tempfile();
+ argv_array_clear(&argv);
if (retval) {
fprintf(stderr, "external diff died, stopping at %s.\n", name);
exit(1);
--
1.9.1.656.ge8a0637
Jeff King