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chase: make struct stat always sync with the opened fd

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Previously, struct stat may not be correctly synced with the currently
opened fd, e.g. when a path contains symlink which points to an absolute
path.

This also rename variables for struct stat, to make them consistent with
the corresponding fd.
This commit is contained in:
Yu Watanabe
2023-04-10 08:40:14 +09:00
parent db0096f2ad
commit ad66c7f1d3
1 changed files with 22 additions and 26 deletions
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src/basic/chase.c
+22 -26
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@@ -77,7 +77,7 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
_cleanup_close_ int fd = -EBADF, root_fd = -EBADF;
unsigned max_follow = CHASE_MAX; /* how many symlinks to follow before giving up and returning ELOOP */
bool exists = true, append_trail_slash = false;
struct stat previous_stat;
struct stat st; /* stat obtained from fd */
const char *todo;
int r;
@@ -218,7 +218,7 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
if (fd < 0)
return -errno;
if (fstat(fd, &previous_stat) < 0)
if (fstat(fd, &st) < 0)
return -errno;
if (flags & CHASE_TRAIL_SLASH)
@@ -227,7 +227,7 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
for (todo = buffer;;) {
_cleanup_free_ char *first = NULL;
_cleanup_close_ int child = -EBADF;
struct stat st;
struct stat st_child;
const char *e;
r = path_find_first_component(&todo, /* accept_dot_dot= */ true, &e);
@@ -248,6 +248,7 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
if (path_equal(first, "..")) {
_cleanup_free_ char *parent = NULL;
_cleanup_close_ int fd_parent = -EBADF;
struct stat st_parent;
/* If we already are at the top, then going up will not change anything. This is
* in-line with how the kernel handles this. */
@@ -258,12 +259,12 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
if (fd_parent < 0)
return -errno;
if (fstat(fd_parent, &st) < 0)
if (fstat(fd_parent, &st_parent) < 0)
return -errno;
/* If we opened the same directory, that means we're at the host root directory, so
* going up won't change anything. */
if (st.st_dev == previous_stat.st_dev && st.st_ino == previous_stat.st_ino)
if (st_parent.st_dev == st.st_dev && st_parent.st_ino == st.st_ino)
continue;
r = path_extract_directory(done, &parent);
@@ -279,18 +280,16 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
if (flags & CHASE_STEP)
goto chased_one;
if (flags & CHASE_SAFE) {
if (unsafe_transition(&previous_stat, &st))
return log_unsafe_transition(fd, fd_parent, path, flags);
previous_stat = st;
}
if (flags & CHASE_SAFE &&
unsafe_transition(&st, &st_parent))
return log_unsafe_transition(fd, fd_parent, path, flags);
if (FLAGS_SET(flags, CHASE_PARENT) && isempty(todo))
break;
/* update fd and stat */
st = st_parent;
close_and_replace(fd, fd_parent);
continue;
}
@@ -322,19 +321,18 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
return r;
}
if (fstat(child, &st) < 0)
if (fstat(child, &st_child) < 0)
return -errno;
if ((flags & CHASE_SAFE) &&
unsafe_transition(&previous_stat, &st))
return log_unsafe_transition(fd, child, path, flags);
previous_stat = st;
if ((flags & CHASE_SAFE) &&
unsafe_transition(&st, &st_child))
return log_unsafe_transition(fd, child, path, flags);
if ((flags & CHASE_NO_AUTOFS) &&
fd_is_fs_type(child, AUTOFS_SUPER_MAGIC) > 0)
return log_autofs_mount_point(child, path, flags);
if (S_ISLNK(st.st_mode) && !((flags & CHASE_NOFOLLOW) && isempty(todo))) {
if (S_ISLNK(st_child.st_mode) && !((flags & CHASE_NOFOLLOW) && isempty(todo))) {
_cleanup_free_ char *destination = NULL;
if (flags & CHASE_PROHIBIT_SYMLINKS)
@@ -361,15 +359,12 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
if (fd < 0)
return fd;
if (flags & CHASE_SAFE) {
if (fstat(fd, &st) < 0)
return -errno;
if (fstat(fd, &st) < 0)
return -errno;
if (unsafe_transition(&previous_stat, &st))
return log_unsafe_transition(child, fd, path, flags);
previous_stat = st;
}
if (flags & CHASE_SAFE &&
unsafe_transition(&st_child, &st))
return log_unsafe_transition(child, fd, path, flags);
r = free_and_strdup(&done, need_absolute ? "/" : NULL);
if (r < 0)
@@ -398,6 +393,7 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
break;
/* And iterate again, but go one directory further down. */
st = st_child;
close_and_replace(fd, child);
}