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do not treat non-symlink reparse points as valid symlinks
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Windows 8 and later can create NFS symlinks (within reparse points)
which we were assuming were normal NTFS symlinks and thus reporting
corrupt paths for.  Add check for reparse points to make sure that
they really are normal symlinks before we try to parse the pathname.

We also should not be parsing other types of reparse points (DFS
junctions etc) as if they were a  symlink so return EOPNOTSUPP
on those.  Also fix endian errors (we were not parsing symlink
lengths as little endian).

This fixes commit d244bf2
which implemented follow link for non-Unix CIFS mounts

CC: Stable <stable@kernel.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>
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Steve French authored and Steve French committed Oct 6, 2013
1 parent e62063d commit c31f330
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Showing 3 changed files with 71 additions and 14 deletions.
31 changes: 23 additions & 8 deletions fs/cifs/cifspdu.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1491,15 +1491,30 @@ struct file_notify_information {
__u8 FileName[0];
} __attribute__((packed));

struct reparse_data {
__u32 ReparseTag;
__u16 ReparseDataLength;
/* For IO_REPARSE_TAG_SYMLINK */
struct reparse_symlink_data {
__le32 ReparseTag;
__le16 ReparseDataLength;
__u16 Reserved;
__u16 SubstituteNameOffset;
__u16 SubstituteNameLength;
__u16 PrintNameOffset;
__u16 PrintNameLength;
__u32 Flags;
__le16 SubstituteNameOffset;
__le16 SubstituteNameLength;
__le16 PrintNameOffset;
__le16 PrintNameLength;
__le32 Flags;
char PathBuffer[0];
} __attribute__((packed));

/* For IO_REPARSE_TAG_NFS */
#define NFS_SPECFILE_LNK 0x00000000014B4E4C
#define NFS_SPECFILE_CHR 0x0000000000524843
#define NFS_SPECFILE_BLK 0x00000000004B4C42
#define NFS_SPECFILE_FIFO 0x000000004F464946
#define NFS_SPECFILE_SOCK 0x000000004B434F53
struct reparse_posix_data {
__le32 ReparseTag;
__le16 ReparseDataLength;
__u16 Reserved;
__le64 InodeType; /* LNK, FIFO, CHR etc. */
char PathBuffer[0];
} __attribute__((packed));

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40 changes: 34 additions & 6 deletions fs/cifs/cifssmb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3088,7 +3088,8 @@ CIFSSMBQuerySymLink(const unsigned int xid, struct cifs_tcon *tcon,
bool is_unicode;
unsigned int sub_len;
char *sub_start;
struct reparse_data *reparse_buf;
struct reparse_symlink_data *reparse_buf;
struct reparse_posix_data *posix_buf;
__u32 data_offset, data_count;
char *end_of_smb;

Expand Down Expand Up @@ -3137,20 +3138,47 @@ CIFSSMBQuerySymLink(const unsigned int xid, struct cifs_tcon *tcon,
goto qreparse_out;
}
end_of_smb = 2 + get_bcc(&pSMBr->hdr) + (char *)&pSMBr->ByteCount;
reparse_buf = (struct reparse_data *)
reparse_buf = (struct reparse_symlink_data *)
((char *)&pSMBr->hdr.Protocol + data_offset);
if ((char *)reparse_buf >= end_of_smb) {
rc = -EIO;
goto qreparse_out;
}
if ((reparse_buf->PathBuffer + reparse_buf->PrintNameOffset +
reparse_buf->PrintNameLength) > end_of_smb) {
if (reparse_buf->ReparseTag == cpu_to_le32(IO_REPARSE_TAG_NFS)) {
cifs_dbg(FYI, "NFS style reparse tag\n");
posix_buf = (struct reparse_posix_data *)reparse_buf;

if (posix_buf->InodeType != cpu_to_le64(NFS_SPECFILE_LNK)) {
cifs_dbg(FYI, "unsupported file type 0x%llx\n",
le64_to_cpu(posix_buf->InodeType));
rc = -EOPNOTSUPP;
goto qreparse_out;
}
is_unicode = true;
sub_len = le16_to_cpu(reparse_buf->ReparseDataLength);
if (posix_buf->PathBuffer + sub_len > end_of_smb) {
cifs_dbg(FYI, "reparse buf beyond SMB\n");
rc = -EIO;
goto qreparse_out;
}
*symlinkinfo = cifs_strndup_from_utf16(posix_buf->PathBuffer,
sub_len, is_unicode, nls_codepage);
goto qreparse_out;
} else if (reparse_buf->ReparseTag !=
cpu_to_le32(IO_REPARSE_TAG_SYMLINK)) {
rc = -EOPNOTSUPP;
goto qreparse_out;
}

/* Reparse tag is NTFS symlink */
sub_start = le16_to_cpu(reparse_buf->SubstituteNameOffset) +
reparse_buf->PathBuffer;
sub_len = le16_to_cpu(reparse_buf->SubstituteNameLength);
if (sub_start + sub_len > end_of_smb) {
cifs_dbg(FYI, "reparse buf beyond SMB\n");
rc = -EIO;
goto qreparse_out;
}
sub_start = reparse_buf->SubstituteNameOffset + reparse_buf->PathBuffer;
sub_len = reparse_buf->SubstituteNameLength;
if (pSMBr->hdr.Flags2 & SMBFLG2_UNICODE)
is_unicode = true;
else
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14 changes: 14 additions & 0 deletions fs/cifs/smbfsctl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -97,9 +97,23 @@
#define FSCTL_QUERY_NETWORK_INTERFACE_INFO 0x001401FC /* BB add struct */
#define FSCTL_SRV_READ_HASH 0x001441BB /* BB add struct */

/* See FSCC 2.1.2.5 */
#define IO_REPARSE_TAG_MOUNT_POINT 0xA0000003
#define IO_REPARSE_TAG_HSM 0xC0000004
#define IO_REPARSE_TAG_SIS 0x80000007
#define IO_REPARSE_TAG_HSM2 0x80000006
#define IO_REPARSE_TAG_DRIVER_EXTENDER 0x80000005
/* Used by the DFS filter. See MS-DFSC */
#define IO_REPARSE_TAG_DFS 0x8000000A
/* Used by the DFS filter See MS-DFSC */
#define IO_REPARSE_TAG_DFSR 0x80000012
#define IO_REPARSE_TAG_FILTER_MANAGER 0x8000000B
/* See section MS-FSCC 2.1.2.4 */
#define IO_REPARSE_TAG_SYMLINK 0xA000000C
#define IO_REPARSE_TAG_DEDUP 0x80000013
#define IO_REPARSE_APPXSTREAM 0xC0000014
/* NFS symlinks, Win 8/SMB3 and later */
#define IO_REPARSE_TAG_NFS 0x80000014

/* fsctl flags */
/* If Flags is set to this value, the request is an FSCTL not ioctl request */
Expand Down

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