git/symlinks.c
Matheus Tavares 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>
2021-03-18 12:58:10 -07:00

342 lines
9.7 KiB
C

#include "cache.h"
static int threaded_check_leading_path(struct cache_def *cache, const char *name,
int len, int warn_on_lstat_err);
static int threaded_has_dirs_only_path(struct cache_def *cache, const char *name, int len, int prefix_len);
/*
* Returns the length (on a path component basis) of the longest
* common prefix match of 'name_a' and 'name_b'.
*/
static int longest_path_match(const char *name_a, int len_a,
const char *name_b, int len_b,
int *previous_slash)
{
int max_len, match_len = 0, match_len_prev = 0, i = 0;
max_len = len_a < len_b ? len_a : len_b;
while (i < max_len && name_a[i] == name_b[i]) {
if (name_a[i] == '/') {
match_len_prev = match_len;
match_len = i;
}
i++;
}
/*
* Is 'name_b' a substring of 'name_a', the other way around,
* or is 'name_a' and 'name_b' the exact same string?
*/
if (i >= max_len && ((len_a > len_b && name_a[len_b] == '/') ||
(len_a < len_b && name_b[len_a] == '/') ||
(len_a == len_b))) {
match_len_prev = match_len;
match_len = i;
}
*previous_slash = match_len_prev;
return match_len;
}
static struct cache_def default_cache = CACHE_DEF_INIT;
static inline void reset_lstat_cache(struct cache_def *cache)
{
strbuf_reset(&cache->path);
cache->flags = 0;
/*
* The track_flags and prefix_len_stat_func members is only
* set by the safeguard rule inside lstat_cache()
*/
}
#define FL_DIR (1 << 0)
#define FL_NOENT (1 << 1)
#define FL_SYMLINK (1 << 2)
#define FL_LSTATERR (1 << 3)
#define FL_ERR (1 << 4)
#define FL_FULLPATH (1 << 5)
/*
* Check if name 'name' of length 'len' has a symlink leading
* component, or if the directory exists and is real, or not.
*
* To speed up the check, some information is allowed to be cached.
* This can be indicated by the 'track_flags' argument, which also can
* be used to indicate that we should check the full path.
*
* The 'prefix_len_stat_func' parameter can be used to set the length
* of the prefix, where the cache should use the stat() function
* instead of the lstat() function to test each path component.
*/
static int lstat_cache_matchlen(struct cache_def *cache,
const char *name, int len,
int *ret_flags, int track_flags,
int prefix_len_stat_func)
{
int match_len, last_slash, last_slash_dir, previous_slash;
int save_flags, ret, saved_errno = 0;
struct stat st;
if (cache->track_flags != track_flags ||
cache->prefix_len_stat_func != prefix_len_stat_func) {
/*
* As a safeguard rule we clear the cache if the
* values of track_flags and/or prefix_len_stat_func
* does not match with the last supplied values.
*/
reset_lstat_cache(cache);
cache->track_flags = track_flags;
cache->prefix_len_stat_func = prefix_len_stat_func;
match_len = last_slash = 0;
} else {
/*
* Check to see if we have a match from the cache for
* the 2 "excluding" path types.
*/
match_len = last_slash =
longest_path_match(name, len, cache->path.buf,
cache->path.len, &previous_slash);
*ret_flags = cache->flags & track_flags & (FL_NOENT|FL_SYMLINK);
if (!(track_flags & FL_FULLPATH) && match_len == len)
match_len = last_slash = previous_slash;
if (*ret_flags && match_len == cache->path.len)
return match_len;
/*
* If we now have match_len > 0, we would know that
* the matched part will always be a directory.
*
* Also, if we are tracking directories and 'name' is
* a substring of the cache on a path component basis,
* we can return immediately.
*/
*ret_flags = track_flags & FL_DIR;
if (*ret_flags && len == match_len)
return match_len;
}
/*
* Okay, no match from the cache so far, so now we have to
* check the rest of the path components.
*/
*ret_flags = FL_DIR;
last_slash_dir = last_slash;
if (len > cache->path.len)
strbuf_grow(&cache->path, len - cache->path.len);
while (match_len < len) {
do {
cache->path.buf[match_len] = name[match_len];
match_len++;
} while (match_len < len && name[match_len] != '/');
if (match_len >= len && !(track_flags & FL_FULLPATH))
break;
last_slash = match_len;
cache->path.buf[last_slash] = '\0';
if (last_slash <= prefix_len_stat_func)
ret = stat(cache->path.buf, &st);
else
ret = lstat(cache->path.buf, &st);
if (ret) {
*ret_flags = FL_LSTATERR;
saved_errno = errno;
if (errno == ENOENT)
*ret_flags |= FL_NOENT;
} else if (S_ISDIR(st.st_mode)) {
last_slash_dir = last_slash;
continue;
} else if (S_ISLNK(st.st_mode)) {
*ret_flags = FL_SYMLINK;
} else {
*ret_flags = FL_ERR;
}
break;
}
/*
* At the end update the cache. Note that max 3 different
* path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
* for the moment!
*/
save_flags = *ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
if (save_flags && last_slash > 0) {
cache->path.buf[last_slash] = '\0';
cache->path.len = last_slash;
cache->flags = save_flags;
} else if ((track_flags & FL_DIR) && last_slash_dir > 0) {
/*
* We have a separate test for the directory case,
* since it could be that we have found a symlink or a
* non-existing directory and the track_flags says
* that we cannot cache this fact, so the cache would
* then have been left empty in this case.
*
* But if we are allowed to track real directories, we
* can still cache the path components before the last
* one (the found symlink or non-existing component).
*/
cache->path.buf[last_slash_dir] = '\0';
cache->path.len = last_slash_dir;
cache->flags = FL_DIR;
} else {
reset_lstat_cache(cache);
}
if (saved_errno)
errno = saved_errno;
return match_len;
}
static int lstat_cache(struct cache_def *cache, const char *name, int len,
int track_flags, int prefix_len_stat_func)
{
int flags;
(void)lstat_cache_matchlen(cache, name, len, &flags, track_flags,
prefix_len_stat_func);
return flags;
}
#define USE_ONLY_LSTAT 0
/*
* Return non-zero if path 'name' has a leading symlink component
*/
int threaded_has_symlink_leading_path(struct cache_def *cache, const char *name, int len)
{
return lstat_cache(cache, name, len, FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) & FL_SYMLINK;
}
int has_symlink_leading_path(const char *name, int len)
{
return threaded_has_symlink_leading_path(&default_cache, name, len);
}
int check_leading_path(const char *name, int len, int warn_on_lstat_err)
{
return threaded_check_leading_path(&default_cache, name, len,
warn_on_lstat_err);
}
/*
* Return zero if some leading path component of 'name' does not exist.
*
* Return -1 if leading path exists and is a directory.
*
* Return the length of a leading component if it either exists but it's not a
* directory, or if we were unable to lstat() it. If warn_on_lstat_err is true,
* also emit a warning for this error.
*/
static int threaded_check_leading_path(struct cache_def *cache, const char *name,
int len, int warn_on_lstat_err)
{
int flags;
int match_len = lstat_cache_matchlen(cache, name, len, &flags,
FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT);
int saved_errno = errno;
if (flags & FL_NOENT)
return 0;
else if (flags & FL_DIR)
return -1;
if (warn_on_lstat_err && (flags & FL_LSTATERR)) {
char *path = xmemdupz(name, match_len);
errno = saved_errno;
warning_errno(_("failed to lstat '%s'"), path);
free(path);
}
return match_len;
}
int has_dirs_only_path(const char *name, int len, int prefix_len)
{
return threaded_has_dirs_only_path(&default_cache, name, len, prefix_len);
}
/*
* Return non-zero if all path components of 'name' exists as a
* directory. If prefix_len > 0, we will test with the stat()
* function instead of the lstat() function for a prefix length of
* 'prefix_len', thus we then allow for symlinks in the prefix part as
* long as those points to real existing directories.
*/
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;
}
static struct strbuf removal = STRBUF_INIT;
static void do_remove_scheduled_dirs(int new_len)
{
while (removal.len > new_len) {
removal.buf[removal.len] = '\0';
if (rmdir(removal.buf))
break;
do {
removal.len--;
} while (removal.len > new_len &&
removal.buf[removal.len] != '/');
}
removal.len = new_len;
}
void schedule_dir_for_removal(const char *name, int len)
{
int match_len, last_slash, i, previous_slash;
match_len = last_slash = i =
longest_path_match(name, len, removal.buf, removal.len,
&previous_slash);
/* Find last slash inside 'name' */
while (i < len) {
if (name[i] == '/')
last_slash = i;
i++;
}
/*
* If we are about to go down the directory tree, we check if
* we must first go upwards the tree, such that we then can
* remove possible empty directories as we go upwards.
*/
if (match_len < last_slash && match_len < removal.len)
do_remove_scheduled_dirs(match_len);
/*
* If we go deeper down the directory tree, we only need to
* save the new path components as we go down.
*/
if (match_len < last_slash)
strbuf_add(&removal, &name[match_len], last_slash - match_len);
}
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;
}