[PATCH] cifs: Add mount option named backup
Shirish Pargaonkar
shirishpargaonkar at gmail.com
Fri Aug 12 13:25:31 MDT 2011
On Fri, Aug 12, 2011 at 12:19 PM, Steve French <smfrench at gmail.com> wrote:
> Shirish or Manoj,
> Could you give a little more detail on the failure scenario
> and which files and information can not be accessed?
>
> A mount option may be the only choice, since there is
> no equivalent for "open for backup intent" open flag,
> and presumably no easy way to query whether a user is a member
> of the "backup operators" group, but would a mount option be
> a problem for other users of the same mount who don't have
> backup operator privilege trying to open other files?
>
> On Fri, Aug 12, 2011 at 11:33 AM, <shirishpargaonkar at gmail.com> wrote:
>> From: Shirish Pargaonkar <shirishpargaonkar at gmail.com>
>>
>>
>> Add mount option backup.
>>
>> It allows an authenticated user to access files with the intent to back them
>> up including their ACLs, who may not have access permission but has
>> "Backup files and directories user right" on them (by virtue of being part
>> of the built-in group Backup Operators.
>>
>> If an authenticated user is not part of the built-in group Backup Operators
>> at the server, access to such files is denied.
>>
>>
>> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar at gmail.com>
>> ---
>> fs/cifs/cifs_fs_sb.h | 1 +
>> fs/cifs/cifsacl.c | 18 +++++++++++++-----
>> fs/cifs/cifsglob.h | 4 +++-
>> fs/cifs/connect.c | 5 +++++
>> fs/cifs/dir.c | 11 +++++++++--
>> fs/cifs/file.c | 14 ++++++++++++--
>> fs/cifs/link.c | 18 +++++++++++++-----
>> 7 files changed, 56 insertions(+), 15 deletions(-)
>>
>> diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
>> index 7260e11..8ba1b44 100644
>> --- a/fs/cifs/cifs_fs_sb.h
>> +++ b/fs/cifs/cifs_fs_sb.h
>> @@ -43,6 +43,7 @@
>> #define CIFS_MOUNT_STRICT_IO 0x40000 /* strict cache mode */
>> #define CIFS_MOUNT_RWPIDFORWARD 0x80000 /* use pid forwarding for rw */
>> #define CIFS_MOUNT_POSIXACL 0x100000 /* mirror of MS_POSIXACL in mnt_cifs_flags */
>> +#define CIFS_MOUNT_CIFS_BACKUP 0x200000 /* open file with backup intent bit */
>>
>> struct cifs_sb_info {
>> struct rb_root tlink_tree;
>> diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
>> index d0f59fa..24bc2dd 100644
>> --- a/fs/cifs/cifsacl.c
>> +++ b/fs/cifs/cifsacl.c
>> @@ -945,7 +945,7 @@ static struct cifs_ntsd *get_cifs_acl_by_path(struct cifs_sb_info *cifs_sb,
>> {
>> struct cifs_ntsd *pntsd = NULL;
>> int oplock = 0;
>> - int xid, rc;
>> + int xid, rc, create_options = 0;
>> __u16 fid;
>> struct cifs_tcon *tcon;
>> struct tcon_link *tlink = cifs_sb_tlink(cifs_sb);
>> @@ -956,9 +956,13 @@ static struct cifs_ntsd *get_cifs_acl_by_path(struct cifs_sb_info *cifs_sb,
>> tcon = tlink_tcon(tlink);
>> xid = GetXid();
>>
>> - rc = CIFSSMBOpen(xid, tcon, path, FILE_OPEN, READ_CONTROL, 0,
>> - &fid, &oplock, NULL, cifs_sb->local_nls,
>> - cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
>> + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL &&
>> + cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUP)
>> + create_options |= CREATE_OPEN_BACKUP_INTENT;
>> +
>> + rc = CIFSSMBOpen(xid, tcon, path, FILE_OPEN, READ_CONTROL,
>> + create_options, &fid, &oplock, NULL, cifs_sb->local_nls,
>> + cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
>> if (!rc) {
>> rc = CIFSSMBGetCIFSACL(xid, tcon, fid, &pntsd, pacllen);
>> CIFSSMBClose(xid, tcon, fid);
>> @@ -995,7 +999,7 @@ static int set_cifs_acl_by_path(struct cifs_sb_info *cifs_sb, const char *path,
>> struct cifs_ntsd *pnntsd, u32 acllen)
>> {
>> int oplock = 0;
>> - int xid, rc;
>> + int xid, rc, create_options = 0;
>> __u16 fid;
>> struct cifs_tcon *tcon;
>> struct tcon_link *tlink = cifs_sb_tlink(cifs_sb);
>> @@ -1006,6 +1010,10 @@ static int set_cifs_acl_by_path(struct cifs_sb_info *cifs_sb, const char *path,
>> tcon = tlink_tcon(tlink);
>> xid = GetXid();
>>
>> + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL &&
>> + cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUP)
>> + create_options |= CREATE_OPEN_BACKUP_INTENT;
>> +
>> rc = CIFSSMBOpen(xid, tcon, path, FILE_OPEN, WRITE_DAC, 0,
>> &fid, &oplock, NULL, cifs_sb->local_nls,
>> cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
>> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
>> index 95dad9d..3c6fd56 100644
>> --- a/fs/cifs/cifsglob.h
>> +++ b/fs/cifs/cifsglob.h
>> @@ -179,6 +179,7 @@ struct smb_vol {
>> bool noperm:1;
>> bool no_psx_acl:1; /* set if posix acl support should be disabled */
>> bool cifs_acl:1;
>> + bool cifs_backup:1; /* to indicates backup intent during file open */
>> bool no_xattr:1; /* set if xattr (EA) support should be disabled*/
>> bool server_ino:1; /* use inode numbers from server ie UniqueId */
>> bool direct_io:1;
>> @@ -219,7 +220,8 @@ struct smb_vol {
>> CIFS_MOUNT_OVERR_GID | CIFS_MOUNT_DYNPERM | \
>> CIFS_MOUNT_NOPOSIXBRL | CIFS_MOUNT_NOSSYNC | \
>> CIFS_MOUNT_FSCACHE | CIFS_MOUNT_MF_SYMLINKS | \
>> - CIFS_MOUNT_MULTIUSER | CIFS_MOUNT_STRICT_IO)
>> + CIFS_MOUNT_MULTIUSER | CIFS_MOUNT_STRICT_IO | \
>> + CIFS_MOUNT_CIFS_BACKUP)
>>
>> #define CIFS_MS_MASK (MS_RDONLY | MS_MANDLOCK | MS_NOEXEC | MS_NOSUID | \
>> MS_NODEV | MS_SYNCHRONOUS)
>> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
>> index 80c2e3a..352d6d6 100644
>> --- a/fs/cifs/connect.c
>> +++ b/fs/cifs/connect.c
>> @@ -883,6 +883,7 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
>> cFYI(1, "Null separator not allowed");
>> }
>> }
>> + vol->cifs_backup = 0; /* no backup intent */
>>
>> while ((data = strsep(&options, separator)) != NULL) {
>> if (!*data)
>> @@ -1405,6 +1406,8 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
>> vol->rwpidforward = 1;
>> } else if (strnicmp(data, "cifsacl", 7) == 0) {
>> vol->cifs_acl = 1;
>> + } else if (strnicmp(data, "backup", 7) == 0) {
>> + vol->cifs_backup = 1;
>> } else if (strnicmp(data, "nocifsacl", 9) == 0) {
>> vol->cifs_acl = 0;
>> } else if (strnicmp(data, "acl", 3) == 0) {
>> @@ -2763,6 +2766,8 @@ void cifs_setup_cifs_sb(struct smb_vol *pvolume_info,
>> cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_RWPIDFORWARD;
>> if (pvolume_info->cifs_acl)
>> cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_CIFS_ACL;
>> + if (pvolume_info->cifs_backup)
>> + cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_CIFS_BACKUP;
>> if (pvolume_info->override_uid)
>> cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_OVERR_UID;
>> if (pvolume_info->override_gid)
>> diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
>> index ae576fb..fbecde6 100644
>> --- a/fs/cifs/dir.c
>> +++ b/fs/cifs/dir.c
>> @@ -243,6 +243,9 @@ cifs_create(struct inode *inode, struct dentry *direntry, int mode,
>> */
>> if (!tcon->unix_ext && (mode & S_IWUGO) == 0)
>> create_options |= CREATE_OPTION_READONLY;
>> + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL &&
>> + cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUP)
>> + create_options |= CREATE_OPEN_BACKUP_INTENT;
>>
>> if (tcon->ses->capabilities & CAP_NT_SMBS)
>> rc = CIFSSMBOpen(xid, tcon, full_path, disposition,
>> @@ -357,6 +360,7 @@ int cifs_mknod(struct inode *inode, struct dentry *direntry, int mode,
>> {
>> int rc = -EPERM;
>> int xid;
>> + int create_options = CREATE_NOT_DIR | CREATE_OPTION_SPECIAL;
>> struct cifs_sb_info *cifs_sb;
>> struct tcon_link *tlink;
>> struct cifs_tcon *pTcon;
>> @@ -431,9 +435,12 @@ int cifs_mknod(struct inode *inode, struct dentry *direntry, int mode,
>> return rc;
>> }
>>
>> - /* FIXME: would WRITE_OWNER | WRITE_DAC be better? */
>> + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL &&
>> + cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUP)
>> + create_options |= CREATE_OPEN_BACKUP_INTENT;
>> +
>> rc = CIFSSMBOpen(xid, pTcon, full_path, FILE_CREATE,
>> - GENERIC_WRITE, CREATE_NOT_DIR | CREATE_OPTION_SPECIAL,
>> + GENERIC_WRITE, create_options,
>> &fileHandle, &oplock, buf, cifs_sb->local_nls,
>> cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
>> if (rc)
>> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
>> index 9f41a10..39b06c4 100644
>> --- a/fs/cifs/file.c
>> +++ b/fs/cifs/file.c
>> @@ -174,6 +174,7 @@ cifs_nt_open(char *full_path, struct inode *inode, struct cifs_sb_info *cifs_sb,
>> int rc;
>> int desiredAccess;
>> int disposition;
>> + int create_options = CREATE_NOT_DIR;
>> FILE_ALL_INFO *buf;
>>
>> desiredAccess = cifs_convert_flags(f_flags);
>> @@ -210,9 +211,13 @@ cifs_nt_open(char *full_path, struct inode *inode, struct cifs_sb_info *cifs_sb,
>> if (!buf)
>> return -ENOMEM;
>>
>> + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL &&
>> + cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUP)
>> + create_options |= CREATE_OPEN_BACKUP_INTENT;
>> +
>> if (tcon->ses->capabilities & CAP_NT_SMBS)
>> rc = CIFSSMBOpen(xid, tcon, full_path, disposition,
>> - desiredAccess, CREATE_NOT_DIR, pnetfid, poplock, buf,
>> + desiredAccess, create_options, pnetfid, poplock, buf,
>> cifs_sb->local_nls, cifs_sb->mnt_cifs_flags
>> & CIFS_MOUNT_MAP_SPECIAL_CHR);
>> else
>> @@ -465,6 +470,7 @@ static int cifs_reopen_file(struct cifsFileInfo *pCifsFile, bool can_flush)
>> char *full_path = NULL;
>> int desiredAccess;
>> int disposition = FILE_OPEN;
>> + int create_options = CREATE_NOT_DIR;
>> __u16 netfid;
>>
>> xid = GetXid();
>> @@ -524,6 +530,10 @@ static int cifs_reopen_file(struct cifsFileInfo *pCifsFile, bool can_flush)
>>
>> desiredAccess = cifs_convert_flags(pCifsFile->f_flags);
>>
>> + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL &&
>> + cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUP)
>> + create_options |= CREATE_OPEN_BACKUP_INTENT;
>> +
>> /* Can not refresh inode by passing in file_info buf to be returned
>> by SMBOpen and then calling get_inode_info with returned buf
>> since file might have write behind data that needs to be flushed
>> @@ -531,7 +541,7 @@ static int cifs_reopen_file(struct cifsFileInfo *pCifsFile, bool can_flush)
>> that inode was not dirty locally we could do this */
>>
>> rc = CIFSSMBOpen(xid, tcon, full_path, disposition, desiredAccess,
>> - CREATE_NOT_DIR, &netfid, &oplock, NULL,
>> + create_options, &netfid, &oplock, NULL,
>> cifs_sb->local_nls, cifs_sb->mnt_cifs_flags &
>> CIFS_MOUNT_MAP_SPECIAL_CHR);
>> if (rc) {
>> diff --git a/fs/cifs/link.c b/fs/cifs/link.c
>> index db3f18c..67e51b8 100644
>> --- a/fs/cifs/link.c
>> +++ b/fs/cifs/link.c
>> @@ -183,14 +183,20 @@ CIFSFormatMFSymlink(u8 *buf, unsigned int buf_len, const char *link_str)
>> static int
>> CIFSCreateMFSymLink(const int xid, struct cifs_tcon *tcon,
>> const char *fromName, const char *toName,
>> - const struct nls_table *nls_codepage, int remap)
>> + struct cifs_sb_info *cifs_sb)
>> {
>> int rc;
>> int oplock = 0;
>> + int remap;
>> + int create_options = CREATE_NOT_DIR;
>> __u16 netfid = 0;
>> u8 *buf;
>> unsigned int bytes_written = 0;
>> struct cifs_io_parms io_parms;
>> + struct nls_table *nls_codepage;
>> +
>> + nls_codepage = cifs_sb->local_nls;
>> + remap = cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR;
>>
>> buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
>> if (!buf)
>> @@ -202,8 +208,12 @@ CIFSCreateMFSymLink(const int xid, struct cifs_tcon *tcon,
>> return rc;
>> }
>>
>> + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL &&
>> + cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUP)
>> + create_options |= CREATE_OPEN_BACKUP_INTENT;
>> +
>> rc = CIFSSMBOpen(xid, tcon, fromName, FILE_CREATE, GENERIC_WRITE,
>> - CREATE_NOT_DIR, &netfid, &oplock, NULL,
>> + create_options, &netfid, &oplock, NULL,
>> nls_codepage, remap);
>> if (rc != 0) {
>> kfree(buf);
>> @@ -559,9 +569,7 @@ cifs_symlink(struct inode *inode, struct dentry *direntry, const char *symname)
>> /* BB what if DFS and this volume is on different share? BB */
>> if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
>> rc = CIFSCreateMFSymLink(xid, pTcon, full_path, symname,
>> - cifs_sb->local_nls,
>> - cifs_sb->mnt_cifs_flags &
>> - CIFS_MOUNT_MAP_SPECIAL_CHR);
>> + cifs_sb);
>> else if (pTcon->unix_ext)
>> rc = CIFSUnixCreateSymLink(xid, pTcon, full_path, symname,
>> cifs_sb->local_nls);
>> --
>> 1.6.0.2
>>
>>
>
>
>
> --
> Thanks,
>
> Steve
>
On a Windows 2003 server, 'Back up files and directories policy is enabled
and user named 'mahalcrow' is added to that policy.
I mount a share from that Windows server by authenticating as user 'mahalcrow'.
# mount -t cifs //cifstest1/myshare /mnt/smb_b -o
backup,cifsacl,user=mahalcrow,pass=<passwd>
# ls -l /mnt/smb_b/testfile2
-rwx------ 1 administrator 10010 18 Aug 9 19:26 /mnt/smb_b/testfile2
# /tmp/getcifsacl /mnt/smb_b/testfile2
REVISION:0x1
CONTROL:0x9404
OWNER:CIFSTESTDOM\Administrator
GROUP:CIFSTESTDOM\Domain Users
ACL:CIFSTESTDOM\Administrator:ALLOWED/0x0/FULL
So with the backup intent create option during open (nt_create_andx),
an user who is neither owner of the file and not part of the only ACE
in the ACL of this file, can still access the file.
Now if I remove this user, mahalcrow, from the policy 'Back up files
and directories' under
Security Settings/Local Policies/user Rights Assignment/Security Options,
unmount and remount the share and then try to access the file
testfile2 from the
mounted share, it fails, even with the backup intent mount option.
# mount -t cifs //cifstest1/myshare /mnt/smb_b -o
backup,cifsacl,user=mahalcrow,pass=<passwd>
# ls -l /mnt/smb_b/testfile2
-rwxr-xr-x 1 root root 18 Aug 9 19:26 /mnt/smb_b/testfile2
# /tmp/getcifsacl /mnt/smb_b/testfile2
getxattr error: 95
REVISION:0x0
CONTROL:0x0
The change in policy on the server will not reflect on an existing smb
connection though,
if this user unmounts and remounts the same share, it would be effective.
Regards,
Shirish
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