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copy: Add COPY_LOCK_BSD

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When making ephemeral copies of files/directories whose cleanup
depends on whether they're locked or not, it's necessary to have the
lock from the very beginning, so let's support that with a new
COPY_LOCK_BSD flag.
This commit is contained in:
Daan De Meyer
2023-03-24 17:12:24 +01:00
parent 0867a46534
commit 01428141ba
3 changed files with 58 additions and 45 deletions
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81
src/shared/copy.c
View File

@@ -167,6 +167,7 @@ int copy_bytes_full(
assert(fdf >= 0);
assert(fdt >= 0);
assert(!FLAGS_SET(copy_flags, COPY_LOCK_BSD));
/* Tries to copy bytes from the file descriptor 'fdf' to 'fdt' in the smartest possible way. Copies a maximum
* of 'max_bytes', which may be specified as UINT64_MAX, in which no maximum is applied. Returns negative on
@@ -931,7 +932,7 @@ static int fd_copy_directory(
_cleanup_close_ int fdf = -EBADF, fdt = -EBADF;
_cleanup_closedir_ DIR *d = NULL;
bool exists, created;
bool exists;
int r;
assert(st);
@@ -961,33 +962,22 @@ static int fd_copy_directory(
if (!d)
return -errno;
exists = false;
if (copy_flags & COPY_MERGE_EMPTY) {
r = dir_is_empty_at(dt, to, /* ignore_hidden_or_backup= */ false);
if (r < 0 && r != -ENOENT)
return r;
else if (r == 1)
exists = true;
}
r = dir_is_empty_at(dt, to, /* ignore_hidden_or_backup= */ false);
if (r < 0 && r != -ENOENT)
return r;
if ((r > 0 && !(copy_flags & (COPY_MERGE|COPY_MERGE_EMPTY))) || (r == 0 && !FLAGS_SET(copy_flags, COPY_MERGE)))
return -EEXIST;
if (exists)
created = false;
else {
if (copy_flags & COPY_MAC_CREATE)
r = mkdirat_label(dt, to, st->st_mode & 07777);
else
r = mkdirat(dt, to, st->st_mode & 07777);
if (r >= 0)
created = true;
else if (errno == EEXIST && (copy_flags & COPY_MERGE))
created = false;
else
return -errno;
}
exists = r >= 0;
fdt = openat(dt, to, O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
fdt = xopenat_lock(dt, to,
O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|(exists ? 0 : O_CREAT|O_EXCL),
(copy_flags & COPY_MAC_CREATE ? XO_LABEL : 0),
st->st_mode & 07777,
copy_flags & COPY_LOCK_BSD ? LOCK_BSD : LOCK_NONE,
LOCK_EX);
if (fdt < 0)
return -errno;
return fdt;
r = 0;
@@ -1063,9 +1053,9 @@ static int fd_copy_directory(
}
q = fd_copy_tree_generic(dirfd(d), de->d_name, &buf, fdt, de->d_name, original_device,
depth_left-1, override_uid, override_gid, copy_flags, denylist,
hardlink_context, child_display_path, progress_path, progress_bytes,
userdata);
depth_left-1, override_uid, override_gid, copy_flags & ~COPY_LOCK_BSD,
denylist, hardlink_context, child_display_path, progress_path,
progress_bytes, userdata);
if (q == -EINTR) /* Propagate SIGINT/SIGTERM up instantly */
return q;
@@ -1076,7 +1066,7 @@ static int fd_copy_directory(
}
finish:
if (created) {
if (!exists) {
if (fchown(fdt,
uid_is_valid(override_uid) ? override_uid : st->st_uid,
gid_is_valid(override_gid) ? override_gid : st->st_gid) < 0)
@@ -1094,7 +1084,7 @@ finish:
return -errno;
}
return r;
return copy_flags & COPY_LOCK_BSD ? TAKE_FD(fdt) : 0;
}
static int fd_copy_leaf(
@@ -1188,6 +1178,7 @@ int copy_tree_at_full(
assert(from);
assert(to);
assert(!FLAGS_SET(copy_flags, COPY_LOCK_BSD));
if (fstatat(fdf, from, &st, AT_SYMLINK_NOFOLLOW) < 0)
return -errno;
@@ -1290,6 +1281,7 @@ int copy_file_fd_at_full(
assert(dir_fdf >= 0 || dir_fdf == AT_FDCWD);
assert(from);
assert(fdt >= 0);
assert(!FLAGS_SET(copy_flags, COPY_LOCK_BSD));
fdf = openat(dir_fdf, from, O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fdf < 0)
@@ -1360,17 +1352,13 @@ int copy_file_at_full(
return r;
WITH_UMASK(0000) {
if (copy_flags & COPY_MAC_CREATE) {
r = mac_selinux_create_file_prepare_at(dir_fdt, to, S_IFREG);
if (r < 0)
return r;
}
fdt = openat(dir_fdt, to, flags|O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY,
mode != MODE_INVALID ? mode : st.st_mode);
if (copy_flags & COPY_MAC_CREATE)
mac_selinux_create_file_clear();
fdt = xopenat_lock(dir_fdt, to,
flags|O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY,
(copy_flags & COPY_MAC_CREATE ? XO_LABEL : 0),
mode != MODE_INVALID ? mode : st.st_mode,
copy_flags & COPY_LOCK_BSD ? LOCK_BSD : LOCK_NONE, LOCK_EX);
if (fdt < 0)
return -errno;
return fdt;
}
if (!FLAGS_SET(flags, O_EXCL)) { /* if O_EXCL was used we created the thing as regular file, no need to check again */
@@ -1382,7 +1370,7 @@ int copy_file_at_full(
if (chattr_mask != 0)
(void) chattr_fd(fdt, chattr_flags, chattr_mask & CHATTR_EARLY_FL, NULL);
r = copy_bytes_full(fdf, fdt, UINT64_MAX, copy_flags, NULL, NULL, progress_bytes, userdata);
r = copy_bytes_full(fdf, fdt, UINT64_MAX, copy_flags & ~COPY_LOCK_BSD, NULL, NULL, progress_bytes, userdata);
if (r < 0)
goto fail;
@@ -1399,9 +1387,11 @@ int copy_file_at_full(
}
}
r = close_nointr(TAKE_FD(fdt)); /* even if this fails, the fd is now invalidated */
if (r < 0)
goto fail;
if (!FLAGS_SET(copy_flags, COPY_LOCK_BSD)) {
r = close_nointr(TAKE_FD(fdt)); /* even if this fails, the fd is now invalidated */
if (r < 0)
goto fail;
}
if (copy_flags & COPY_FSYNC_FULL) {
r = fsync_parent_at(dir_fdt, to);
@@ -1409,7 +1399,7 @@ int copy_file_at_full(
goto fail;
}
return 0;
return copy_flags & COPY_LOCK_BSD ? TAKE_FD(fdt) : 0;
fail:
/* Only unlink if we definitely are the ones who created the file */
@@ -1437,6 +1427,7 @@ int copy_file_atomic_at_full(
assert(from);
assert(to);
assert(!FLAGS_SET(copy_flags, COPY_LOCK_BSD));
if (copy_flags & COPY_MAC_CREATE) {
r = mac_selinux_create_file_prepare_at(dir_fdt, to, S_IFREG);

1
src/shared/copy.h
View File

@@ -29,6 +29,7 @@ typedef enum CopyFlags {
COPY_HOLES = 1 << 14, /* Copy holes */
COPY_GRACEFUL_WARN = 1 << 15, /* Skip copying file types that aren't supported by the target filesystem */
COPY_TRUNCATE = 1 << 16, /* Truncate to current file offset after copying */
COPY_LOCK_BSD = 1 << 17, /* Return a BSD exclusively locked file descriptor referring to the copied image/directory. */
} CopyFlags;
typedef enum DenyType {

21
src/test/test-copy.c
View File

@@ -1,5 +1,6 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <sys/file.h>
#include <sys/xattr.h>
#include <unistd.h>
@@ -435,4 +436,24 @@ TEST_RET(copy_holes) {
return 0;
}
TEST(copy_lock) {
_cleanup_(rm_rf_physical_and_freep) char *t = NULL;
_cleanup_close_ int tfd = -EBADF, fd = -EBADF;
assert_se((tfd = mkdtemp_open(NULL, 0, &t)) >= 0);
assert_se(mkdirat(tfd, "abc", 0755) >= 0);
assert_se(write_string_file_at(tfd, "abc/def", "abc", WRITE_STRING_FILE_CREATE) >= 0);
assert_se((fd = copy_directory_at(tfd, "abc", tfd, "qed", COPY_LOCK_BSD)) >= 0);
assert_se(faccessat(tfd, "qed", F_OK, 0) >= 0);
assert_se(faccessat(tfd, "qed/def", F_OK, 0) >= 0);
assert_se(xopenat_lock(tfd, "qed", 0, 0, 0, LOCK_BSD, LOCK_EX|LOCK_NB) == -EAGAIN);
fd = safe_close(fd);
assert_se((fd = copy_file_at(tfd, "abc/def", tfd, "poi", 0, 0644, COPY_LOCK_BSD)));
assert_se(read_file_at_and_streq(tfd, "poi", "abc\n"));
assert_se(xopenat_lock(tfd, "poi", 0, 0, 0, LOCK_BSD, LOCK_EX|LOCK_NB) == -EAGAIN);
fd = safe_close(fd);
}
DEFINE_TEST_MAIN(LOG_DEBUG);