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Merge pull request #33496 from YHNdnzj/fd-is-mount-symlink

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mountpoint-util: do not assume symlinks are not mountpoints
This commit is contained in:
Luca Boccassi 2024-07-02 10:07:20 +02:00 committed by GitHub
commit 5dfce2296c
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2 changed files with 30 additions and 4 deletions
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4
src/basic/mountpoint-util.c
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@ -273,8 +273,6 @@ int fd_is_mount_point(int fd, const char *filename, int flags) {
/* If statx() is not available or forbidden, fall back to name_to_handle_at() below */
} else if (FLAGS_SET(sx.stx_attributes_mask, STATX_ATTR_MOUNT_ROOT)) /* yay! */
return FLAGS_SET(sx.stx_attributes, STATX_ATTR_MOUNT_ROOT);
else if (FLAGS_SET(sx.stx_mask, STATX_TYPE) && S_ISLNK(sx.stx_mode))
return false; /* symlinks are never mount points */
r = name_to_handle_at_try_fid(fd, filename, &h, &mount_id, flags);
if (r < 0) {
@ -350,8 +348,6 @@ fallback_fstat:
flags |= AT_SYMLINK_NOFOLLOW;
if (fstatat(fd, filename, &a, flags) < 0)
return -errno;
if (S_ISLNK(a.st_mode)) /* Symlinks are never mount points */
return false;
if (isempty(filename))
r = fstatat(fd, "..", &b, 0);

30
src/test/test-mountpoint-util.c
View File

@ -10,6 +10,7 @@
#include "fileio.h"
#include "hashmap.h"
#include "log.h"
#include "missing_syscall.h"
#include "mountpoint-util.h"
#include "path-util.h"
#include "rm-rf.h"
@ -317,6 +318,35 @@ TEST(fd_is_mount_point) {
r = fd_is_mount_point(fd, NULL, 0);
assert_se(IN_SET(r, 0, -ENOTDIR)); /* on old kernels we can't determine if regular files are mount points if we have no directory fd */
assert_se(fd_is_mount_point(fd, "", 0) == -EINVAL);
if (!mount_new_api_supported())
return;
/* Symlinks can be mount points with new mount API */
_cleanup_close_ int mfd = -EBADF, rfd = -EBADF;
_cleanup_free_ char *t = NULL;
struct stat st;
safe_close(fd);
ASSERT_OK_ERRNO(fd = open(tmpdir, O_DIRECTORY|O_PATH|O_CLOEXEC));
ASSERT_OK_ERRNO(symlinkat("/usr", fd, "symlink"));
mfd = open_tree(fd, "symlink", AT_SYMLINK_NOFOLLOW|OPEN_TREE_CLONE|OPEN_TREE_CLOEXEC);
if (mfd < 0 && ERRNO_IS_PRIVILEGE(errno))
return;
ASSERT_OK_ERRNO(mfd);
ASSERT_OK_ERRNO(rfd = openat(fd, "regular", O_CLOEXEC|O_CREAT|O_EXCL, 0644));
ASSERT_OK_ERRNO(move_mount(mfd, "", rfd, "", MOVE_MOUNT_F_EMPTY_PATH|MOVE_MOUNT_T_EMPTY_PATH));
ASSERT_OK_ERRNO(fstatat(fd, "regular", &st, AT_SYMLINK_NOFOLLOW));
ASSERT_OK(stat_verify_symlink(&st));
ASSERT_OK(readlinkat_malloc(fd, "regular", &t));
ASSERT_STREQ(t, "/usr");
ASSERT_OK(fd_is_mount_point(fd, "regular", 0));
}
TEST(ms_nosymfollow_supported) {