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mount-util: fix fd_is_mount_point() when both the parent and directory are network fs

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The second call to name_to_handle_at_loop() didn't check for the specific
errors that can happen when the parent dir is mounted by nfs and instead of
falling back like it's done for the child dir, fd_is_mount_point() failed in
this case.
This commit is contained in:
Franck Bui 2021-09-30 14:05:36 +02:00 committed by Zbigniew Jędrzejewski-Szmek
parent 8e9b3bcf12
commit 964ccab828
1 changed files with 42 additions and 28 deletions
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70
src/basic/mountpoint-util.c
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@ -157,6 +157,19 @@ static bool filename_possibly_with_slash_suffix(const char *s) {
return filename_is_valid(copied);
}
static bool is_name_to_handle_at_fatal_error(int err) {
/* name_to_handle_at() can return "acceptable" errors that are due to the context. For
* example the kernel does not support name_to_handle_at() at all (ENOSYS), or the syscall
* was blocked (EACCES/EPERM; maybe through seccomp, because we are running inside of a
* container), or the mount point is not triggered yet (EOVERFLOW, think nfs4), or some
* general name_to_handle_at() flakiness (EINVAL). However other errors are not supposed to
* happen and therefore are considered fatal ones. */
assert(err < 0);
return !IN_SET(err, -EOPNOTSUPP, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW, -EINVAL);
}
int fd_is_mount_point(int fd, const char *filename, int flags) {
_cleanup_free_ struct file_handle *h = NULL, *h_parent = NULL;
int mount_id = -1, mount_id_parent = -1;
@ -206,39 +219,40 @@ int fd_is_mount_point(int fd, const char *filename, int flags) {
return false; /* symlinks are never mount points */
r = name_to_handle_at_loop(fd, filename, &h, &mount_id, flags);
if (IN_SET(r, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW, -EINVAL))
/* This kernel does not support name_to_handle_at() at all (ENOSYS), or the syscall was blocked
* (EACCES/EPERM; maybe through seccomp, because we are running inside of a container?), or the mount
* point is not triggered yet (EOVERFLOW, think nfs4), or some general name_to_handle_at() flakiness
* (EINVAL): fall back to simpler logic. */
goto fallback_fdinfo;
else if (r == -EOPNOTSUPP)
/* This kernel or file system does not support name_to_handle_at(), hence let's see if the upper fs
* supports it (in which case it is a mount point), otherwise fall back to the traditional stat()
* logic */
if (r < 0) {
if (is_name_to_handle_at_fatal_error(r))
return r;
if (r != -EOPNOTSUPP)
goto fallback_fdinfo;
/* This kernel or file system does not support name_to_handle_at(), hence let's see
* if the upper fs supports it (in which case it is a mount point), otherwise fall
* back to the traditional stat() logic */
nosupp = true;
else if (r < 0)
return r;
}
r = name_to_handle_at_loop(fd, "", &h_parent, &mount_id_parent, AT_EMPTY_PATH);
if (r == -EOPNOTSUPP) {
if (nosupp)
/* Neither parent nor child do name_to_handle_at()? We have no choice but to fall back. */
if (r < 0) {
if (is_name_to_handle_at_fatal_error(r))
return r;
if (r != -EOPNOTSUPP)
goto fallback_fdinfo;
if (nosupp)
/* Both the parent and the directory can't do name_to_handle_at() */
goto fallback_fdinfo;
else
/* The parent can't do name_to_handle_at() but the directory we are interested in can? If so,
* it must be a mount point. */
return 1;
} else if (r < 0)
return r;
/* The parent can do name_to_handle_at() but the directory we are interested in can't? If so, it must
* be a mount point. */
/* The parent can't do name_to_handle_at() but the directory we are
* interested in can? If so, it must be a mount point. */
return 1;
}
/* The parent can do name_to_handle_at() but the directory we are interested in can't? If
* so, it must be a mount point. */
if (nosupp)
return 1;
/* If the file handle for the directory we are interested in and its parent are identical, we assume
* this is the root directory, which is a mount point. */
/* If the file handle for the directory we are interested in and its parent are identical,
* we assume this is the root directory, which is a mount point. */
if (h->handle_bytes == h_parent->handle_bytes &&
h->handle_type == h_parent->handle_type &&
@ -338,10 +352,10 @@ int path_get_mnt_id(const char *path, int *ret) {
}
r = name_to_handle_at_loop(AT_FDCWD, path, NULL, ret, 0);
if (IN_SET(r, -EOPNOTSUPP, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW, -EINVAL)) /* kernel/fs don't support this, or seccomp blocks access, or untriggered mount, or name_to_handle_at() is flaky */
return fd_fdinfo_mnt_id(AT_FDCWD, path, 0, ret);
if (r == 0 || is_name_to_handle_at_fatal_error(r))
return r;
return r;
return fd_fdinfo_mnt_id(AT_FDCWD, path, 0, ret);
}
bool fstype_is_network(const char *fstype) {