Sync with 2.21.4

* maint-2.21:
  Git 2.21.4
  Git 2.20.5
  Git 2.19.6
  Git 2.18.5
  Git 2.17.6
  unpack_trees(): start with a fresh lstat cache
  run-command: invalidate lstat cache after a command finished
  checkout: fix bug that makes checkout follow symlinks in leading path

Author: dscho

Documentation/RelNotes/2.17.6.txt

@@ -0,0 +1,16 @@
+Git v2.17.6 Release Notes
+=========================
+
+This release addresses the security issues CVE-2021-21300.
+
+Fixes since v2.17.5
+-------------------
+
+ * CVE-2021-21300:
+   On case-insensitive file systems with support for symbolic links,
+   if Git is configured globally to apply delay-capable clean/smudge
+   filters (such as Git LFS), Git could be fooled into running
+   remote code during a clone.
+
+Credit for finding and fixing this vulnerability goes to Matheus
+Tavares, helped by Johannes Schindelin.

Documentation/RelNotes/2.18.5.txt

@@ -0,0 +1,6 @@
+Git v2.18.5 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.17.6 to address
+the security issue CVE-2021-21300; see the release notes for that
+version for details.

Documentation/RelNotes/2.19.6.txt

@@ -0,0 +1,6 @@
+Git v2.19.6 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.17.6 and
+v2.18.5 to address the security issue CVE-2021-21300; see the
+release notes for these versions for details.

Documentation/RelNotes/2.20.5.txt

@@ -0,0 +1,6 @@
+Git v2.20.5 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.17.6, v2.18.5
+and v2.19.6 to address the security issue CVE-2021-21300; see
+the release notes for these versions for details.

Documentation/RelNotes/2.21.4.txt

@@ -0,0 +1,6 @@
+Git v2.21.4 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.17.6, v2.18.5,
+v2.19.6 and v2.20.5 to address the security issue CVE-2021-21300;
+see the release notes for these versions for details.

cache.h

@@ -1654,6 +1654,7 @@ int has_symlink_leading_path(const char *name, int len);
 int threaded_has_symlink_leading_path(struct cache_def *, const char *, int);
 int check_leading_path(const char *name, int len);
 int has_dirs_only_path(const char *name, int len, int prefix_len);
+void invalidate_lstat_cache(void);
 void schedule_dir_for_removal(const char *name, int len);
 void remove_scheduled_dirs(void);
 

compat/mingw.c

@@ -340,6 +340,8 @@ int mingw_rmdir(const char *pathname)
 	       ask_yes_no_if_possible("Deletion of directory '%s' failed. "
 			"Should I try again?", pathname))
 	       ret = _wrmdir(wpathname);
+	if (!ret)
+		invalidate_lstat_cache();
 	return ret;
 }
 

git-compat-util.h

@@ -355,6 +355,11 @@ static inline int noop_core_config(const char *var, const char *value, void *cb)
 #define platform_core_config noop_core_config
 #endif
 
+int lstat_cache_aware_rmdir(const char *path);
+#if !defined(__MINGW32__) && !defined(_MSC_VER)
+#define rmdir lstat_cache_aware_rmdir
+#endif
+
 #ifndef has_dos_drive_prefix
 static inline int git_has_dos_drive_prefix(const char *path)
 {

run-command.c

@@ -989,6 +989,7 @@ int finish_command(struct child_process *cmd)
 	int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 	trace2_child_exit(cmd, ret);
 	child_process_clear(cmd);
+	invalidate_lstat_cache();
 	return ret;
 }
 
@@ -1289,13 +1290,19 @@ int start_async(struct async *async)
 int finish_async(struct async *async)
 {
 #ifdef NO_PTHREADS
-	return wait_or_whine(async->pid, "child process", 0);
+	int ret = wait_or_whine(async->pid, "child process", 0);
+
+	invalidate_lstat_cache();
+
+	return ret;
 #else
 	void *ret = (void *)(intptr_t)(-1);
 
 	if (pthread_join(async->tid, &ret))
 		error("pthread_join failed");
+	invalidate_lstat_cache();
 	return (int)(intptr_t)ret;
+
 #endif
 }
 

symlinks.c

@@ -267,6 +267,13 @@ int has_dirs_only_path(const char *name, int len, int prefix_len)
  */
 static int threaded_has_dirs_only_path(struct cache_def *cache, const char *name, int len, int prefix_len)
 {
+	/*
+	 * Note: this function is used by the checkout machinery, which also
+	 * takes care to properly reset the cache when it performs an operation
+	 * that would leave the cache outdated. If this function starts caching
+	 * anything else besides FL_DIR, remember to also invalidate the cache
+	 * when creating or deleting paths that might be in the cache.
+	 */
 	return lstat_cache(cache, name, len,
 			   FL_DIR|FL_FULLPATH, prefix_len) &
 		FL_DIR;
@@ -321,3 +328,20 @@ void remove_scheduled_dirs(void)
 {
 	do_remove_scheduled_dirs(0);
 }
+
+void invalidate_lstat_cache(void)
+{
+	reset_lstat_cache(&default_cache);
+}
+
+#undef rmdir
+int lstat_cache_aware_rmdir(const char *path)
+{
+	/* Any change in this function must be made also in `mingw_rmdir()` */
+	int ret = rmdir(path);
+
+	if (!ret)
+		invalidate_lstat_cache();
+
+	return ret;
+}