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smbd: Simplify OpenDir_from_pathref()

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Use the /proc/self/fd trick to make get_real_filename_fullscan_at look
a bit nicer and faster in strace. Direct SMB_VFS_OPENAT also is
cheaper in user space, we don't need the full fd_openat and
non_widelink_open magic here.

Also avoid opening ".", which can fail where a full path open would
succeed: If the directory in question does not give "x" perms to the
user, we get a handle on the dir as such but can't cd into it.

I haven't seen real-world cases of this, but one of our tests creates
such a scenario. I have further refactoring in my local tree that make
this patch necessary.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
This commit is contained in:
Volker Lendecke 2024-10-10 17:16:02 +02:00 committed by Ralph Boehme
parent 9550f4370e
commit c0bbeded93
3 changed files with 41 additions and 55 deletions
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46
source3/smbd/dir.c
View File

@ -1066,19 +1066,55 @@ NTSTATUS OpenDir_from_pathref(TALLOC_CTX *mem_ctx,
uint32_t attr,
struct smb_Dir **_dir_hnd)
{
struct files_struct *fsp = NULL;
struct connection_struct *conn = dirfsp->conn;
struct files_struct *new_fsp = NULL;
struct smb_Dir *dir_hnd = NULL;
const struct vfs_open_how how = {.flags = O_RDONLY | O_DIRECTORY};
int old_fd;
NTSTATUS status;
status = openat_internal_dir_from_pathref(dirfsp, O_RDONLY, &fsp);
status = create_internal_dirfsp(conn, dirfsp->fsp_name, &new_fsp);
if (!NT_STATUS_IS_OK(status)) {
return status;
}
status = OpenDir_fsp(mem_ctx, fsp->conn, fsp, mask, attr, &dir_hnd);
if (dirfsp->fsp_flags.have_proc_fds &&
((old_fd = fsp_get_pathref_fd(dirfsp)) != -1))
{
struct sys_proc_fd_path_buf buf;
struct smb_filename proc_fname = {
.base_name = sys_proc_fd_path(old_fd, &buf),
};
int new_fd;
new_fd = SMB_VFS_OPENAT(
conn, conn->cwd_fsp, &proc_fname, new_fsp, &how);
if (new_fd == -1) {
status = map_nt_error_from_unix(errno);
DBG_DEBUG("SMB_VFS_OPENAT(%s) returned %s\n",
proc_fname.base_name, strerror(errno));
file_free(NULL, new_fsp);
return status;
}
fsp_set_fd(new_fsp, new_fd);
} else {
status = fd_openat(conn->cwd_fsp,
dirfsp->fsp_name,
new_fsp,
&how);
if (!NT_STATUS_IS_OK(status)) {
DBG_DEBUG("fd_openat(%s) returned %s\n",
dirfsp->fsp_name->base_name,
nt_errstr(status));
file_free(NULL, new_fsp);
return status;
}
}
status = OpenDir_fsp(mem_ctx, conn, new_fsp, mask, attr, &dir_hnd);
if (!NT_STATUS_IS_OK(status)) {
fd_close(fsp);
file_free(NULL, fsp);
fd_close(new_fsp);
file_free(NULL, new_fsp);
return status;
}

46
source3/smbd/files.c
View File

@ -286,52 +286,6 @@ NTSTATUS open_internal_dirfsp(connection_struct *conn,
return NT_STATUS_OK;
}
/*
* Convert a pathref dirfsp into a real fsp. No need to do any cwd
* tricks, we just open ".".
*/
NTSTATUS openat_internal_dir_from_pathref(
struct files_struct *dirfsp,
int _open_flags,
struct files_struct **_fsp)
{
struct connection_struct *conn = dirfsp->conn;
struct smb_filename *smb_dname = dirfsp->fsp_name;
struct files_struct *fsp = NULL;
char dot[] = ".";
struct smb_filename smb_dot = {
.base_name = dot,
.flags = smb_dname->flags,
.twrp = smb_dname->twrp,
};
struct vfs_open_how how = { .flags = _open_flags, };
NTSTATUS status;
status = create_internal_dirfsp(conn, smb_dname, &fsp);
if (!NT_STATUS_IS_OK(status)) {
return status;
}
/*
* Pointless for opening ".", but you never know...
*/
how.flags |= O_NOFOLLOW;
status = fd_openat(dirfsp, &smb_dot, fsp, &how);
if (!NT_STATUS_IS_OK(status)) {
DBG_INFO("fd_openat(\"%s\", \".\") failed: %s\n",
fsp_str_dbg(dirfsp),
nt_errstr(status));
file_free(NULL, fsp);
return status;
}
fsp->fsp_name->st = smb_dname->st;
fsp->file_id = vfs_file_id_from_sbuf(conn, &fsp->fsp_name->st);
*_fsp = fsp;
return NT_STATUS_OK;
}
/*
* The "link" in the name doesn't imply link in the filesystem
* sense. It's a object that "links" together an fsp and an smb_fname

4
source3/smbd/proto.h
View File

@ -366,10 +366,6 @@ NTSTATUS open_internal_dirfsp(connection_struct *conn,
const struct smb_filename *smb_dname,
int open_flags,
struct files_struct **_fsp);
NTSTATUS openat_internal_dir_from_pathref(
struct files_struct *dirfsp,
int open_flags,
struct files_struct **_fsp);
NTSTATUS openat_pathref_fsp(const struct files_struct *dirfsp,
struct smb_filename *smb_fname);