@matheusbsbs / matheus-bagliano / commits / fab78a0c3d

checkout: don't follow symlinks when removing entries

At 1d718a5108 ("do not overwrite untracked symlinks", 2011-02-20), symlink.c:check_leading_path() started returning different codes for FL_ENOENT and FL_SYMLINK. But one of its callers, unlink_entry(), was not adjusted for this change, so it started to follow symlinks on the leading path of to-be-removed entries. Fix that and add a regression test. Note that since 1d718a5108 check_leading_path() no longer differentiates the case where it found a symlink in the path's leading components from the cases where it found a regular file or failed to lstat() the component. So, a side effect of this current patch is that unlink_entry() now returns early in all of these three cases. And because we no longer try to unlink such paths, we also don't get the warning from remove_or_warn(). For the regular file and symlink cases, it's questionable whether the warning was useful in the first place: unlink_entry() removes tracked paths that should no longer be present in the state we are checking out to. If the path had its leading dir replaced by another file, it means that the basename already doesn't exist, so there is no need for a warning. Sure, we are leaving a regular file or symlink behind at the path's dirname, but this file is either untracked now (so again, no need to warn), or it will be replaced by a tracked file during the next phase of this checkout operation. As for failing to lstat() one of the leading components, the basename might still exist only we cannot unlink it (e.g. due to the lack of the required permissions). Since the user expect it to be removed (especially with checkout's --no-overlay option), add back the warning in this more relevant case. Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Matheus Tavares committed Mar 18, 2021 at 15:43 UTC fab78a0c3defddff87ea5aa7dd32c5e444c43f1f

5 files changed +37 -11

cache.h

+1 -1

@@ -1744,7 +1744,7 @@ static inline void cache_def_clear(struct cache_def *cache)

1744

1745 int has_symlink_leading_path(const char *name, int len);

1746 int threaded_has_symlink_leading_path(struct cache_def *, const char *, int);

1747 -int check_leading_path(const char *name, int len);

1747 +int check_leading_path(const char *name, int len, int warn_on_lstat_err);

1748 int has_dirs_only_path(const char *name, int len, int prefix_len);

1749 void invalidate_lstat_cache(void);

1750 void schedule_dir_for_removal(const char *name, int len);

entry.c

+1 -1

@@ -530,7 +530,7 @@ void unlink_entry(const struct cache_entry *ce)

530 submodule_move_head(ce->name, "HEAD", NULL,

531 SUBMODULE_MOVE_HEAD_FORCE);

532 }

533 - if (!check_leading_path(ce->name, ce_namelen(ce)))

533 + if (check_leading_path(ce->name, ce_namelen(ce), 1) >= 0)

534 return;

535 if (remove_or_warn(ce->ce_mode, ce->name))

536 return;

symlinks.c

+22 -8

@@ -1,6 +1,7 @@

1 #include "cache.h"

3 -static int threaded_check_leading_path(struct cache_def *cache, const char *name, int len);

3 +static int threaded_check_leading_path(struct cache_def *cache, const char *name,

4 + int len, int warn_on_lstat_err);

5 static int threaded_has_dirs_only_path(struct cache_def *cache, const char *name, int len, int prefix_len);

7 /*

@@ -72,7 +73,7 @@ static int lstat_cache_matchlen(struct cache_def *cache,

73 int prefix_len_stat_func)

74 {

75 int match_len, last_slash, last_slash_dir, previous_slash;

75 - int save_flags, ret;

76 + int save_flags, ret, saved_errno = 0;

77 struct stat st;

79 if (cache->track_flags != track_flags ||

@@ -139,6 +140,7 @@ static int lstat_cache_matchlen(struct cache_def *cache,

140

141 if (ret) {

142 *ret_flags = FL_LSTATERR;

143 + saved_errno = errno;

144 if (errno == ENOENT)

145 *ret_flags |= FL_NOENT;

146 } else if (S_ISDIR(st.st_mode)) {

@@ -180,6 +182,8 @@ static int lstat_cache_matchlen(struct cache_def *cache,

182 } else {

183 reset_lstat_cache(cache);

184 }

185 + if (saved_errno)

186 + errno = saved_errno;

187 return match_len;

188 }

189

@@ -207,9 +211,10 @@ int has_symlink_leading_path(const char *name, int len)

211 return threaded_has_symlink_leading_path(&default_cache, name, len);

212 }

213

210 -int check_leading_path(const char *name, int len)

214 +int check_leading_path(const char *name, int len, int warn_on_lstat_err)

215 {

212 - return threaded_check_leading_path(&default_cache, name, len);

216 + return threaded_check_leading_path(&default_cache, name, len,

217 + warn_on_lstat_err);

218 }

219

220 /*

@@ -218,19 +223,28 @@ int check_leading_path(const char *name, int len)

223 * Return -1 if leading path exists and is a directory.

224 *

225 * Return the length of a leading component if it either exists but it's not a

221 - * directory, or if we were unable to lstat() it.

226 + * directory, or if we were unable to lstat() it. If warn_on_lstat_err is true,

227 + * also emit a warning for this error.

228 */

223 -static int threaded_check_leading_path(struct cache_def *cache, const char *name, int len)

229 +static int threaded_check_leading_path(struct cache_def *cache, const char *name,

230 + int len, int warn_on_lstat_err)

231 {

232 int flags;

233 int match_len = lstat_cache_matchlen(cache, name, len, &flags,

234 FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT);

235 + int saved_errno = errno;

236 +

237 if (flags & FL_NOENT)

238 return 0;

239 else if (flags & FL_DIR)

240 return -1;

232 - else

233 - return match_len;

241 + if (warn_on_lstat_err && (flags & FL_LSTATERR)) {

242 + char *path = xmemdupz(name, match_len);

243 + errno = saved_errno;

244 + warning_errno(_("failed to lstat '%s'"), path);

245 + free(path);

246 + }

247 + return match_len;

248 }

249

250 int has_dirs_only_path(const char *name, int len, int prefix_len)

t/t2021-checkout-overwrite.sh

+12

@@ -51,4 +51,16 @@ test_expect_success SYMLINKS 'the symlink remained' '

51 test -h a/b

52 '

54 +test_expect_success SYMLINKS 'checkout -f must not follow symlinks when removing entries' '

55 + git checkout -f start &&

56 + mkdir dir &&

57 + >dir/f &&

58 + git add dir/f &&

59 + git commit -m "add dir/f" &&

60 + mv dir untracked &&

61 + ln -s untracked dir &&

62 + git checkout -f HEAD~ &&

63 + test_path_is_file untracked/f

64 +'

65 +

66 test_done

unpack-trees.c

+1 -1

@@ -2098,7 +2098,7 @@ static int verify_absent_1(const struct cache_entry *ce,

2098 if (o->index_only || o->reset || !o->update)

2099 return 0;

2100

2101 - len = check_leading_path(ce->name, ce_namelen(ce));

2101 + len = check_leading_path(ce->name, ce_namelen(ce), 0);

2102 if (!len)

2103 return 0;

2104 else if (len > 0) {