Merge branch 'jk/diagnose-config-mmap-failure' into maint

The configuration reader/writer uses mmap(2) interface to access
the files; when we find a directory, it barfed with "Out of memory?".

* jk/diagnose-config-mmap-failure:
  xmmap(): drop "Out of memory?"
  config.c: rewrite ENODEV into EISDIR when mmap fails
  config.c: avoid xmmap error messages
  config.c: fix mmap leak when writing config
  read-cache.c: drop PROT_WRITE from mmap of index

config.c

@@ -1937,6 +1937,8 @@ int git_config_set_multivar_in_file(const char *config_filename,
 	int ret;
 	struct lock_file *lock = NULL;
 	char *filename_buf = NULL;
+	char *contents = NULL;
+	size_t contents_sz;
 
 	/* parse-key returns negative; flip the sign to feed exit(3) */
 	ret = 0 - git_config_parse_key(key, &store.key, &store.baselen);
@@ -1986,8 +1988,7 @@ int git_config_set_multivar_in_file(const char *config_filename,
 			goto write_err_out;
 	} else {
 		struct stat st;
-		char *contents;
-		size_t contents_sz, copy_begin, copy_end;
+		size_t copy_begin, copy_end;
 		int i, new_line = 0;
 
 		if (value_regex == NULL)
@@ -2050,8 +2051,17 @@ int git_config_set_multivar_in_file(const char *config_filename,
 
 		fstat(in_fd, &st);
 		contents_sz = xsize_t(st.st_size);
-		contents = xmmap(NULL, contents_sz, PROT_READ,
+		contents = xmmap_gently(NULL, contents_sz, PROT_READ,
 					MAP_PRIVATE, in_fd, 0);
+		if (contents == MAP_FAILED) {
+			if (errno == ENODEV && S_ISDIR(st.st_mode))
+				errno = EISDIR;
+			error("unable to mmap '%s': %s",
+			      config_filename, strerror(errno));
+			ret = CONFIG_INVALID_FILE;
+			contents = NULL;
+			goto out_free;
+		}
 		close(in_fd);
 
 		if (chmod(lock->filename.buf, st.st_mode & 07777) < 0) {
@@ -2106,8 +2116,6 @@ int git_config_set_multivar_in_file(const char *config_filename,
 					  contents_sz - copy_begin) <
 			    contents_sz - copy_begin)
 				goto write_err_out;
-
-		munmap(contents, contents_sz);
 	}
 
 	if (commit_lock_file(lock) < 0) {
@@ -2133,6 +2141,8 @@ out_free:
 	if (lock)
 		rollback_lock_file(lock);
 	free(filename_buf);
+	if (contents)
+		munmap(contents, contents_sz);
 	return ret;
 
 write_err_out:

git-compat-util.h

@@ -717,6 +717,7 @@ extern char *xstrndup(const char *str, size_t len);
 extern void *xrealloc(void *ptr, size_t size);
 extern void *xcalloc(size_t nmemb, size_t size);
 extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);
+extern void *xmmap_gently(void *start, size_t length, int prot, int flags, int fd, off_t offset);
 extern ssize_t xread(int fd, void *buf, size_t len);
 extern ssize_t xwrite(int fd, const void *buf, size_t len);
 extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);

read-cache.c

@@ -1540,7 +1540,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	if (mmap_size < sizeof(struct cache_header) + 20)
 		die("index file smaller than expected");
 
-	mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+	mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (mmap == MAP_FAILED)
 		die_errno("unable to map index file");
 	close(fd);

sha1_file.c

@@ -707,7 +707,7 @@ static void mmap_limit_check(size_t length)
 		    (uintmax_t)length, (uintmax_t)limit);
 }
 
-void *xmmap(void *start, size_t length,
+void *xmmap_gently(void *start, size_t length,
 		  int prot, int flags, int fd, off_t offset)
 {
 	void *ret;
@@ -719,12 +719,19 @@ void *xmmap(void *start, size_t length,
 			return NULL;
 		release_pack_memory(length);
 		ret = mmap(start, length, prot, flags, fd, offset);
-		if (ret == MAP_FAILED)
-			die_errno("Out of memory? mmap failed");
 	}
 	return ret;
 }
 
+void *xmmap(void *start, size_t length,
+	int prot, int flags, int fd, off_t offset)
+{
+	void *ret = xmmap_gently(start, length, prot, flags, fd, offset);
+	if (ret == MAP_FAILED)
+		die_errno("mmap failed");
+	return ret;
+}
+
 void close_pack_windows(struct packed_git *p)
 {
 	while (p->windows) {