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-rw-r--r--src/basic/copy.c105
1 files changed, 58 insertions, 47 deletions
diff --git a/src/basic/copy.c b/src/basic/copy.c
index 5b53f2e0f..bb17d3ae3 100644
--- a/src/basic/copy.c
+++ b/src/basic/copy.c
@@ -1,7 +1,5 @@
/* SPDX-License-Identifier: LGPL-2.1+ */
/***
- This file is part of systemd.
-
Copyright 2014 Lennart Poettering
***/
@@ -29,6 +27,7 @@
#include "io-util.h"
//#include "macro.h"
#include "missing.h"
+//#include "mount-util.h"
//#include "string-util.h"
#include "strv.h"
#include "time-util.h"
@@ -36,7 +35,12 @@
#include "user-util.h"
//#include "xattr-util.h"
-#define COPY_BUFFER_SIZE (16*1024u)
+#define COPY_BUFFER_SIZE (16U*1024U)
+
+/* A safety net for descending recursively into file system trees to copy. On Linux PATH_MAX is 4096, which means the
+ * deepest valid path one can build is around 2048, which we hence use as a safety net here, to not spin endlessly in
+ * case of bind mount cycles and suchlike. */
+#define COPY_DEPTH_MAX 2048U
static ssize_t try_copy_file_range(
int fd_in, loff_t *off_in,
@@ -482,6 +486,7 @@ static int fd_copy_directory(
int dt,
const char *to,
dev_t original_device,
+ unsigned depth_left,
uid_t override_uid,
gid_t override_gid,
CopyFlags copy_flags) {
@@ -495,6 +500,9 @@ static int fd_copy_directory(
assert(st);
assert(to);
+ if (depth_left == 0)
+ return -ENAMETOOLONG;
+
if (from)
fdf = openat(df, from, O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
else
@@ -533,13 +541,40 @@ static int fd_copy_directory(
continue;
}
- if (buf.st_dev != original_device)
- continue;
+ if (S_ISDIR(buf.st_mode)) {
+ /*
+ * Don't descend into directories on other file systems, if this is requested. We do a simple
+ * .st_dev check here, which basically comes for free. Note that we do this check only on
+ * directories, not other kind of file system objects, for two reason:
+ *
+ * • The kernel's overlayfs pseudo file system that overlays multiple real file systems
+ * propagates the .st_dev field of the file system a file originates from all the way up
+ * through the stack to stat(). It doesn't do that for directories however. This means that
+ * comparing .st_dev on non-directories suggests that they all are mount points. To avoid
+ * confusion we hence avoid relying on this check for regular files.
+ *
+ * • The main reason we do this check at all is to protect ourselves from bind mount cycles,
+ * where we really want to avoid descending down in all eternity. However the .st_dev check
+ * is usually not sufficient for this protection anyway, as bind mount cycles from the same
+ * file system onto itself can't be detected that way. (Note we also do a recursion depth
+ * check, which is probably the better protection in this regard, which is why
+ * COPY_SAME_MOUNT is optional).
+ */
+
+ if (FLAGS_SET(copy_flags, COPY_SAME_MOUNT)) {
+ if (buf.st_dev != original_device)
+ continue;
+
+ r = fd_is_mount_point(dirfd(d), de->d_name, 0);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ continue;
+ }
- if (S_ISREG(buf.st_mode))
+ q = fd_copy_directory(dirfd(d), de->d_name, &buf, fdt, de->d_name, original_device, depth_left-1, override_uid, override_gid, copy_flags);
+ } else if (S_ISREG(buf.st_mode))
q = fd_copy_regular(dirfd(d), de->d_name, &buf, fdt, de->d_name, override_uid, override_gid, copy_flags);
- else if (S_ISDIR(buf.st_mode))
- q = fd_copy_directory(dirfd(d), de->d_name, &buf, fdt, de->d_name, original_device, override_uid, override_gid, copy_flags);
else if (S_ISLNK(buf.st_mode))
q = fd_copy_symlink(dirfd(d), de->d_name, &buf, fdt, de->d_name, override_uid, override_gid, copy_flags);
else if (S_ISFIFO(buf.st_mode))
@@ -589,7 +624,7 @@ int copy_tree_at(int fdf, const char *from, int fdt, const char *to, uid_t overr
if (S_ISREG(st.st_mode))
return fd_copy_regular(fdf, from, &st, fdt, to, override_uid, override_gid, copy_flags);
else if (S_ISDIR(st.st_mode))
- return fd_copy_directory(fdf, from, &st, fdt, to, st.st_dev, override_uid, override_gid, copy_flags);
+ return fd_copy_directory(fdf, from, &st, fdt, to, st.st_dev, COPY_DEPTH_MAX, override_uid, override_gid, copy_flags);
else if (S_ISLNK(st.st_mode))
return fd_copy_symlink(fdf, from, &st, fdt, to, override_uid, override_gid, copy_flags);
else if (S_ISFIFO(st.st_mode))
@@ -616,7 +651,7 @@ int copy_directory_fd(int dirfd, const char *to, CopyFlags copy_flags) {
if (!S_ISDIR(st.st_mode))
return -ENOTDIR;
- return fd_copy_directory(dirfd, NULL, &st, AT_FDCWD, to, st.st_dev, UID_INVALID, GID_INVALID, copy_flags);
+ return fd_copy_directory(dirfd, NULL, &st, AT_FDCWD, to, st.st_dev, COPY_DEPTH_MAX, UID_INVALID, GID_INVALID, copy_flags);
}
int copy_directory(const char *from, const char *to, CopyFlags copy_flags) {
@@ -631,7 +666,7 @@ int copy_directory(const char *from, const char *to, CopyFlags copy_flags) {
if (!S_ISDIR(st.st_mode))
return -ENOTDIR;
- return fd_copy_directory(AT_FDCWD, from, &st, AT_FDCWD, to, st.st_dev, UID_INVALID, GID_INVALID, copy_flags);
+ return fd_copy_directory(AT_FDCWD, from, &st, AT_FDCWD, to, st.st_dev, COPY_DEPTH_MAX, UID_INVALID, GID_INVALID, copy_flags);
}
int copy_file_fd(const char *from, int fdt, CopyFlags copy_flags) {
@@ -684,55 +719,31 @@ int copy_file(const char *from, const char *to, int flags, mode_t mode, unsigned
}
int copy_file_atomic(const char *from, const char *to, mode_t mode, unsigned chattr_flags, CopyFlags copy_flags) {
- _cleanup_(unlink_and_freep) char *t = NULL;
- _cleanup_close_ int fdt = -1;
+ _cleanup_free_ char *t = NULL;
int r;
assert(from);
assert(to);
- /* We try to use O_TMPFILE here to create the file if we can. Note that that only works if COPY_REPLACE is not
- * set though as we need to use linkat() for linking the O_TMPFILE file into the file system but that system
- * call can't replace existing files. Hence, if COPY_REPLACE is set we create a temporary name in the file
- * system right-away and unconditionally which we then can renameat() to the right name after we completed
- * writing it. */
-
- if (copy_flags & COPY_REPLACE) {
- r = tempfn_random(to, NULL, &t);
- if (r < 0)
- return r;
-
- fdt = open(t, O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY|O_WRONLY|O_CLOEXEC, 0600);
- if (fdt < 0) {
- t = mfree(t);
- return -errno;
- }
- } else {
- fdt = open_tmpfile_linkable(to, O_WRONLY|O_CLOEXEC, &t);
- if (fdt < 0)
- return fdt;
- }
-
- if (chattr_flags != 0)
- (void) chattr_fd(fdt, chattr_flags, (unsigned) -1);
-
- r = copy_file_fd(from, fdt, copy_flags);
+ r = tempfn_random(to, NULL, &t);
if (r < 0)
return r;
- if (fchmod(fdt, mode) < 0)
- return -errno;
+ r = copy_file(from, t, O_NOFOLLOW|O_EXCL, mode, chattr_flags, copy_flags);
+ if (r < 0)
+ return r;
if (copy_flags & COPY_REPLACE) {
- if (renameat(AT_FDCWD, t, AT_FDCWD, to) < 0)
- return -errno;
- } else {
- r = link_tmpfile(fdt, t, to);
+ r = renameat(AT_FDCWD, t, AT_FDCWD, to);
if (r < 0)
- return r;
+ r = -errno;
+ } else
+ r = rename_noreplace(AT_FDCWD, t, AT_FDCWD, to);
+ if (r < 0) {
+ (void) unlink(t);
+ return r;
}
- t = mfree(t);
return 0;
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-24 12:46:44 +0000