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[PATCH v3 5/9] init: remove git_init_db_config() while fixing leaks

From
Andrzej Hunt via GitGitGadget <gitgitgadget@gmail.com>
Date
Mar 21, 2021, 16:58 UTC
Message-ID
<b615fda790f0f8a61a0e836617e19d760f3b063c.1616345918.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.899.v3.git.1616345918.gitgitgadget@gmail.com>
From: Andrzej Hunt <ajrhunt@google.com>
The primary goal of this change is to stop leaking init_db_template_dir.
This leak can happen because:
 1. git_init_db_config() allocates new memory into init_db_template_dir
    without first freeing the existing value.
 2. init_db_template_dir might already contain data, either because:
  2.1 git_config() can be invoked twice with this callback in a single
      process - at least 2 allocations are likely.
  2.2 A single git_config() allocation can invoke the callback multiple
      times for a given key (see further explanation in the function
      docs) - each of those calls will trigger another leak.

The simplest fix for the leak would be to free(init_db_template_dir) before overwriting it. Instead we choose to convert to fetching init.templatedir via git_config_get_value() as that is more explicit, more efficient, and avoids allocations (the returned result is owned by the config cache, so we aren't responsible for freeing it).

If we remove init_db_template_dir, git_init_db_config() ends up being responsible only for forwarding core.* config values to platform_core_config(). However platform_core_config() already ignores non-core.* config values, so we can safely remove git_init_db_config() and invoke git_config() directly with platform_core_config() as the callback.

The platform_core_config forwarding was originally added in:
  287853392a (mingw: respect core.hidedotfiles = false in git-init again, 2019-03-11
And I suspect the potential for a leak existed since the original
implementation of git_init_db_config in:
  90b45187ba (Add `init.templatedir` configuration variable., 2010-02-17)
LSAN output from t0001:
Direct leak of 73 byte(s) in 1 object(s) allocated from:
    #0 0x49a859 in realloc /home/abuild/rpmbuild/BUILD/llvm-11.0.0.src/build/../projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
    #1 0x9a7276 in xrealloc /home/ahunt/oss-fuzz/git/wrapper.c:126:8
    #2 0x9362ad in strbuf_grow /home/ahunt/oss-fuzz/git/strbuf.c:98:2
    #3 0x936eaa in strbuf_add /home/ahunt/oss-fuzz/git/strbuf.c:295:2
    #4 0x868112 in strbuf_addstr /home/ahunt/oss-fuzz/git/./strbuf.h:304:2
    #5 0x86a8ad in expand_user_path /home/ahunt/oss-fuzz/git/path.c:758:2
    #6 0x720bb1 in git_config_pathname /home/ahunt/oss-fuzz/git/config.c:1287:10
    #7 0x5960e2 in git_init_db_config /home/ahunt/oss-fuzz/git/builtin/init-db.c:161:11
    #8 0x7255b8 in configset_iter /home/ahunt/oss-fuzz/git/config.c:1982:7
    #9 0x7253fc in repo_config /home/ahunt/oss-fuzz/git/config.c:2311:2
    #10 0x725ca7 in git_config /home/ahunt/oss-fuzz/git/config.c:2399:2
    #11 0x593e8d in create_default_files /home/ahunt/oss-fuzz/git/builtin/init-db.c:225:2
    #12 0x5935c6 in init_db /home/ahunt/oss-fuzz/git/builtin/init-db.c:449:11
    #13 0x59588e in cmd_init_db /home/ahunt/oss-fuzz/git/builtin/init-db.c:714:9
    #14 0x4cd60d in run_builtin /home/ahunt/oss-fuzz/git/git.c:453:11
    #15 0x4cb2da in handle_builtin /home/ahunt/oss-fuzz/git/git.c:704:3
    #16 0x4ccc37 in run_argv /home/ahunt/oss-fuzz/git/git.c:771:4
    #17 0x4cac29 in cmd_main /home/ahunt/oss-fuzz/git/git.c:902:19
    #18 0x69c4de in main /home/ahunt/oss-fuzz/git/common-main.c:52:11
    #19 0x7f23552d6349 in __libc_start_main (/lib64/libc.so.6+0x24349)
Signed-off-by: Andrzej Hunt <ajrhunt@google.com>
---
 builtin/init-db.c | 28 +++++++---------------------
 1 file changed, 7 insertions(+), 21 deletions(-)
diff --git a/builtin/init-db.c b/builtin/init-db.c
index dcc45bef5148..d31dbc883746 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -25,7 +25,6 @@
 
 static int init_is_bare_repository = 0;
 static int init_shared_repository = -1;
-static const char *init_db_template_dir;
 
 static void copy_templates_1(struct strbuf *path, struct strbuf *template_path,
 			     DIR *dir)
@@ -94,7 +93,7 @@ static void copy_templates_1(struct strbuf *path, struct strbuf *template_path,
 	}
 }
 
-static void copy_templates(const char *template_dir)
+static void copy_templates(const char *template_dir, const char *init_template_dir)
 {
 	struct strbuf path = STRBUF_INIT;
 	struct strbuf template_path = STRBUF_INIT;
@@ -107,7 +106,7 @@ static void copy_templates(const char *template_dir)
 	if (!template_dir)
 		template_dir = getenv(TEMPLATE_DIR_ENVIRONMENT);
 	if (!template_dir)
-		template_dir = init_db_template_dir;
+		template_dir = init_template_dir;
 	if (!template_dir)
 		template_dir = to_free = system_path(DEFAULT_GIT_TEMPLATE_DIR);
 	if (!template_dir[0]) {
@@ -154,17 +153,6 @@ static void copy_templates(const char *template_dir)
 	clear_repository_format(&template_format);
 }
 
-static int git_init_db_config(const char *k, const char *v, void *cb)
-{
-	if (!strcmp(k, "init.templatedir"))
-		return git_config_pathname(&init_db_template_dir, k, v);
-
-	if (starts_with(k, "core."))
-		return platform_core_config(k, v, cb);
-
-	return 0;
-}
-
 /*
  * If the git_dir is not directly inside the working tree, then git will not
  * find it by default, and we need to set the worktree explicitly.
@@ -212,10 +200,7 @@ static int create_default_files(const char *template_path,
 	int reinit;
 	int filemode;
 	struct strbuf err = STRBUF_INIT;
-
-	/* Just look for `init.templatedir` */
-	init_db_template_dir = NULL; /* re-set in case it was set before */
-	git_config(git_init_db_config, NULL);
+	const char *init_template_dir = NULL;
 
 	/*
 	 * First copy the templates -- we might have the default
@@ -226,7 +211,8 @@ static int create_default_files(const char *template_path,
 	 * values (since we've just potentially changed what's available on
 	 * disk).
 	 */
-	copy_templates(template_path);
+	git_config_get_value("init.templatedir", &init_template_dir);
+	copy_templates(template_path, init_template_dir);
 	git_config_clear();
 	reset_shared_repository();
 	git_config(git_default_config, NULL);
@@ -422,8 +408,8 @@ int init_db(const char *git_dir, const char *real_git_dir,
 	}
 	startup_info->have_repository = 1;
 
-	/* Just look for `core.hidedotfiles` */
-	git_config(git_init_db_config, NULL);
+	/* Ensure `core.hidedotfiles` is processed */
+	git_config(platform_core_config, NULL);
 
 	safe_create_dir(git_dir, 0);
 

-- 
gitgitgadget
Previous: Andrzej Hunt via GitGitGadgetNext: Andrzej Hunt via GitGitGadget
Message 49 of 52 in “Fix all leaks in t0001”
  1. 0/7 Fix all leaks in t0001Andrzej Hunt via GitGitGadget, Mar 8, 2021
  2. 1/7 symbolic-ref: don't leak shortened refname in check_symref()Andrzej Hunt via GitGitGadget, Mar 8, 2021
  3. Jeff KingMar 8, 2021
  4. Andrzej HuntMar 14, 2021
  5. 2/7 reset: free instead of leaking unneeded refAndrzej Hunt via GitGitGadget, Mar 8, 2021
  6. Jeff KingMar 8, 2021
  7. 3/7 clone: free or UNLEAK further pointers when finishedAndrzej Hunt via GitGitGadget, Mar 8, 2021
  8. Jeff KingMar 8, 2021
  9. Andrzej HuntMar 14, 2021
  10. 6/7 init-db: silence template_dir leak when converting to absolute pathAndrzej Hunt via GitGitGadget, Mar 8, 2021
  11. Jeff KingMar 8, 2021
  12. 4/7 worktree: fix leak in dwim_branch()Andrzej Hunt via GitGitGadget, Mar 8, 2021
  13. Jeff KingMar 8, 2021
  14. Andrzej HuntMar 14, 2021
  15. 7/7 parse-options: don't leak alias help messagesAndrzej Hunt via GitGitGadget, Mar 8, 2021
  16. Jeff KingMar 8, 2021
  17. Andrzej HuntMar 14, 2021
  18. 5/7 init: remove git_init_db_config() while fixing leaksAndrzej Hunt via GitGitGadget, Mar 8, 2021
  19. Jeff KingMar 8, 2021
  20. Jeff KingMar 8, 2021
  21. Junio C HamanoMar 12, 2021
  22. Andrzej HuntMar 14, 2021
  23. Andrzej HuntMar 15, 2021
  24. Junio C HamanoMar 8, 2021
  25. Andrzej HuntMar 14, 2021
  26. 0/9 Fix all leaks in t0001Andrzej Hunt via GitGitGadget, Mar 14, 2021
  27. 8/9 parse-options: don't leak alias help messagesAndrzej Hunt via GitGitGadget, Mar 14, 2021
  28. Eric SunshineMar 14, 2021
  29. Andrzej HuntMar 15, 2021
  30. Andrzej HuntMar 14, 2021
  31. 1/9 symbolic-ref: don't leak shortened refname in check_symref()Andrzej Hunt via GitGitGadget, Mar 14, 2021
  32. 7/9 parse-options: convert bitfield values to use binary shiftAndrzej Hunt via GitGitGadget, Mar 14, 2021
  33. Martin ÅgrenMar 14, 2021
  34. Junio C HamanoMar 14, 2021
  35. Andrzej HuntMar 15, 2021
  36. 4/9 worktree: fix leak in dwim_branch()Andrzej Hunt via GitGitGadget, Mar 14, 2021
  37. 5/9 init: remove git_init_db_config() while fixing leaksAndrzej Hunt via GitGitGadget, Mar 14, 2021
  38. 3/9 clone: free or UNLEAK further pointers when finishedAndrzej Hunt via GitGitGadget, Mar 14, 2021
  39. 2/9 reset: free instead of leaking unneeded refAndrzej Hunt via GitGitGadget, Mar 14, 2021
  40. 9/9 transport: also free remote_refs in transport_disconnect()Andrzej Hunt via GitGitGadget, Mar 14, 2021
  41. 6/9 init-db: silence template_dir leak when converting to absolute pathAndrzej Hunt via GitGitGadget, Mar 14, 2021
  42. 0/9 Fix all leaks in t0001Andrzej Hunt via GitGitGadget, Mar 21, 2021
  43. 1/9 symbolic-ref: don't leak shortened refname in check_symref()Andrzej Hunt via GitGitGadget, Mar 21, 2021
  44. 2/9 reset: free instead of leaking unneeded refAndrzej Hunt via GitGitGadget, Mar 21, 2021
  45. 4/9 worktree: fix leak in dwim_branch()Andrzej Hunt via GitGitGadget, Mar 21, 2021
  46. 3/9 clone: free or UNLEAK further pointers when finishedAndrzej Hunt via GitGitGadget, Mar 21, 2021
  47. 7/9 parse-options: convert bitfield values to use binary shiftAndrzej Hunt via GitGitGadget, Mar 21, 2021
  48. 6/9 init-db: silence template_dir leak when converting to absolute pathAndrzej Hunt via GitGitGadget, Mar 21, 2021
  49. 5/9 init: remove git_init_db_config() while fixing leaksAndrzej Hunt via GitGitGadget, Mar 21, 2021
  50. 9/9 transport: also free remote_refs in transport_disconnect()Andrzej Hunt via GitGitGadget, Mar 21, 2021
  51. 8/9 parse-options: don't leak alias help messagesAndrzej Hunt via GitGitGadget, Mar 21, 2021
  52. Junio C HamanoMar 21, 2021

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