cifs: fix crash for querying symlinks stored as reparse-points
diff mbox series

Message ID 20190627045702.8701-1-lsahlber@redhat.com
State New
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Series
  • cifs: fix crash for querying symlinks stored as reparse-points
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Commit Message

Ronnie Sahlberg June 27, 2019, 4:57 a.m. UTC
We never parsed/returned any data from .get_link() when the object is a windows reparse-point
containing a symlink. This results in the VFS layer oopsing accessing an uninitialized buffer:

...
[  171.407172] Call Trace:
[  171.408039]  readlink_copy+0x29/0x70
[  171.408872]  vfs_readlink+0xc1/0x1f0
[  171.409709]  ? readlink_copy+0x70/0x70
[  171.410565]  ? simple_attr_release+0x30/0x30
[  171.411446]  ? getname_flags+0x105/0x2a0
[  171.412231]  do_readlinkat+0x1b7/0x1e0
[  171.412938]  ? __ia32_compat_sys_newfstat+0x30/0x30
...

Fix this by adding code to handle these buffers and make sure we do return a valid buffer
to .get_link()

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
---
 fs/cifs/smb2ops.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 fs/cifs/smb2pdu.h | 16 +++++++++++++-
 2 files changed, 75 insertions(+), 5 deletions(-)

Comments

Steve French June 27, 2019, 5:30 a.m. UTC | #1
removed the duplicate definition of IO_REPARSE_TAG_SYMLINK and
tentatively merged to cifs-2.6.git for-next but looks good so far in
testing.


On Wed, Jun 26, 2019 at 11:57 PM Ronnie Sahlberg <lsahlber@redhat.com> wrote:
>
> We never parsed/returned any data from .get_link() when the object is a windows reparse-point
> containing a symlink. This results in the VFS layer oopsing accessing an uninitialized buffer:
>
> ...
> [  171.407172] Call Trace:
> [  171.408039]  readlink_copy+0x29/0x70
> [  171.408872]  vfs_readlink+0xc1/0x1f0
> [  171.409709]  ? readlink_copy+0x70/0x70
> [  171.410565]  ? simple_attr_release+0x30/0x30
> [  171.411446]  ? getname_flags+0x105/0x2a0
> [  171.412231]  do_readlinkat+0x1b7/0x1e0
> [  171.412938]  ? __ia32_compat_sys_newfstat+0x30/0x30
> ...
>
> Fix this by adding code to handle these buffers and make sure we do return a valid buffer
> to .get_link()
>
> CC: Stable <stable@vger.kernel.org>
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
>  fs/cifs/smb2ops.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++----
>  fs/cifs/smb2pdu.h | 16 +++++++++++++-
>  2 files changed, 75 insertions(+), 5 deletions(-)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index e921e6511728..74c826007069 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -2385,6 +2385,41 @@ smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
>         kfree(dfs_rsp);
>         return rc;
>  }
> +
> +static int
> +parse_reparse_symlink(struct reparse_symlink_data_buffer *symlink_buf,
> +                     u32 plen, char **target_path,
> +                     struct cifs_sb_info *cifs_sb)
> +{
> +       unsigned int sub_len;
> +       unsigned int sub_offset;
> +
> +       /* We only handle Symbolic Link : MS-FSCC 2.1.2.4 */
> +       if (le32_to_cpu(symlink_buf->ReparseTag) != REPARSE_TAG_SYMLINK) {
> +               cifs_dbg(VFS, "srv returned invalid symlink buffer\n");
> +               return -EIO;
> +       }
> +
> +       sub_offset = le16_to_cpu(symlink_buf->SubstituteNameOffset);
> +       sub_len = le16_to_cpu(symlink_buf->SubstituteNameLength);
> +       if (sub_offset + 20 > plen ||
> +           sub_offset + sub_len + 20 > plen) {
> +               cifs_dbg(VFS, "srv returned malformed symlink buffer\n");
> +               return -EIO;
> +       }
> +
> +       *target_path = cifs_strndup_from_utf16(
> +                               symlink_buf->PathBuffer + sub_offset,
> +                               sub_len, true, cifs_sb->local_nls);
> +       if (!(*target_path))
> +               return -ENOMEM;
> +
> +       convert_delimiter(*target_path, '/');
> +       cifs_dbg(FYI, "%s: target path: %s\n", __func__, *target_path);
> +
> +       return 0;
> +}
> +
>  #define SMB2_SYMLINK_STRUCT_SIZE \
>         (sizeof(struct smb2_err_rsp) - 1 + sizeof(struct smb2_symlink_err_rsp))
>
> @@ -2414,11 +2449,13 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
>         struct kvec close_iov[1];
>         struct smb2_create_rsp *create_rsp;
>         struct smb2_ioctl_rsp *ioctl_rsp;
> -       char *ioctl_buf;
> +       struct reparse_data_buffer *reparse_buf;
>         u32 plen;
>
>         cifs_dbg(FYI, "%s: path: %s\n", __func__, full_path);
>
> +       *target_path = NULL;
> +
>         if (smb3_encryption_required(tcon))
>                 flags |= CIFS_TRANSFORM_REQ;
>
> @@ -2496,17 +2533,36 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
>         if ((rc == 0) && (is_reparse_point)) {
>                 /* See MS-FSCC 2.3.23 */
>
> -               ioctl_buf = (char *)ioctl_rsp + le32_to_cpu(ioctl_rsp->OutputOffset);
> +               reparse_buf = (struct reparse_data_buffer *)
> +                       ((char *)ioctl_rsp +
> +                        le32_to_cpu(ioctl_rsp->OutputOffset));
>                 plen = le32_to_cpu(ioctl_rsp->OutputCount);
>
>                 if (plen + le32_to_cpu(ioctl_rsp->OutputOffset) >
>                     rsp_iov[1].iov_len) {
> -                       cifs_dbg(VFS, "srv returned invalid ioctl length: %d\n", plen);
> +                       cifs_dbg(VFS, "srv returned invalid ioctl len: %d\n",
> +                                plen);
> +                       rc = -EIO;
> +                       goto querty_exit;
> +               }
> +
> +               if (plen < 8) {
> +                       cifs_dbg(VFS, "reparse buffer is too small. Must be "
> +                                "at least 8 bytes but was %d\n", plen);
> +                       rc = -EIO;
> +                       goto querty_exit;
> +               }
> +
> +               if (plen < le16_to_cpu(reparse_buf->ReparseDataLength) + 8) {
> +                       cifs_dbg(VFS, "srv returned invalid reparse buf "
> +                                "length: %d\n", plen);
>                         rc = -EIO;
>                         goto querty_exit;
>                 }
>
> -               /* Do stuff with ioctl_buf/plen */
> +               rc = parse_reparse_symlink(
> +                       (struct reparse_symlink_data_buffer *)reparse_buf,
> +                       plen, target_path, cifs_sb);
>                 goto querty_exit;
>         }
>
> diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
> index c7d5813bebd8..31f7c56e0ed8 100644
> --- a/fs/cifs/smb2pdu.h
> +++ b/fs/cifs/smb2pdu.h
> @@ -888,6 +888,8 @@ struct file_allocated_range_buffer {
>
>  /* struct fsctl_reparse_info_req is empty, only response structs (see below) */
>
> +#define REPARSE_TAG_SYMLINK 0xa000000c
> +
>  struct reparse_data_buffer {
>         __le32  ReparseTag;
>         __le16  ReparseDataLength;
> @@ -914,7 +916,19 @@ struct reparse_mount_point_data_buffer {
>         __u8    PathBuffer[0]; /* Variable Length */
>  } __packed;
>
> -/* See MS-FSCC 2.1.2.4 and cifspdu.h for struct reparse_symlink_data */
> +#define SYMLINK_FLAG_RELATIVE 0x00000001
> +
> +struct reparse_symlink_data_buffer {
> +       __le32  ReparseTag;
> +       __le16  ReparseDataLength;
> +       __u16   Reserved;
> +       __le16  SubstituteNameOffset;
> +       __le16  SubstituteNameLength;
> +       __le16  PrintNameOffset;
> +       __le16  PrintNameLength;
> +       __le32  Flags;
> +       __u8    PathBuffer[0]; /* Variable Length */
> +} __packed;
>
>  /* See MS-FSCC 2.1.2.6 and cifspdu.h for struct reparse_posix_data */
>
> --
> 2.13.6
>

Patch
diff mbox series

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index e921e6511728..74c826007069 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2385,6 +2385,41 @@  smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
 	kfree(dfs_rsp);
 	return rc;
 }
+
+static int
+parse_reparse_symlink(struct reparse_symlink_data_buffer *symlink_buf,
+		      u32 plen, char **target_path,
+		      struct cifs_sb_info *cifs_sb)
+{
+	unsigned int sub_len;
+	unsigned int sub_offset;
+
+	/* We only handle Symbolic Link : MS-FSCC 2.1.2.4 */
+	if (le32_to_cpu(symlink_buf->ReparseTag) != REPARSE_TAG_SYMLINK) {
+		cifs_dbg(VFS, "srv returned invalid symlink buffer\n");
+		return -EIO;
+	}
+
+	sub_offset = le16_to_cpu(symlink_buf->SubstituteNameOffset);
+	sub_len = le16_to_cpu(symlink_buf->SubstituteNameLength);
+	if (sub_offset + 20 > plen ||
+	    sub_offset + sub_len + 20 > plen) {
+		cifs_dbg(VFS, "srv returned malformed symlink buffer\n");
+		return -EIO;
+	}
+
+	*target_path = cifs_strndup_from_utf16(
+				symlink_buf->PathBuffer + sub_offset,
+				sub_len, true, cifs_sb->local_nls);
+	if (!(*target_path))
+		return -ENOMEM;
+
+	convert_delimiter(*target_path, '/');
+	cifs_dbg(FYI, "%s: target path: %s\n", __func__, *target_path);
+
+	return 0;
+}
+
 #define SMB2_SYMLINK_STRUCT_SIZE \
 	(sizeof(struct smb2_err_rsp) - 1 + sizeof(struct smb2_symlink_err_rsp))
 
@@ -2414,11 +2449,13 @@  smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 	struct kvec close_iov[1];
 	struct smb2_create_rsp *create_rsp;
 	struct smb2_ioctl_rsp *ioctl_rsp;
-	char *ioctl_buf;
+	struct reparse_data_buffer *reparse_buf;
 	u32 plen;
 
 	cifs_dbg(FYI, "%s: path: %s\n", __func__, full_path);
 
+	*target_path = NULL;
+
 	if (smb3_encryption_required(tcon))
 		flags |= CIFS_TRANSFORM_REQ;
 
@@ -2496,17 +2533,36 @@  smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 	if ((rc == 0) && (is_reparse_point)) {
 		/* See MS-FSCC 2.3.23 */
 
-		ioctl_buf = (char *)ioctl_rsp + le32_to_cpu(ioctl_rsp->OutputOffset);
+		reparse_buf = (struct reparse_data_buffer *)
+			((char *)ioctl_rsp +
+			 le32_to_cpu(ioctl_rsp->OutputOffset));
 		plen = le32_to_cpu(ioctl_rsp->OutputCount);
 
 		if (plen + le32_to_cpu(ioctl_rsp->OutputOffset) >
 		    rsp_iov[1].iov_len) {
-			cifs_dbg(VFS, "srv returned invalid ioctl length: %d\n", plen);
+			cifs_dbg(VFS, "srv returned invalid ioctl len: %d\n",
+				 plen);
+			rc = -EIO;
+			goto querty_exit;
+		}
+
+		if (plen < 8) {
+			cifs_dbg(VFS, "reparse buffer is too small. Must be "
+				 "at least 8 bytes but was %d\n", plen);
+			rc = -EIO;
+			goto querty_exit;
+		}
+
+		if (plen < le16_to_cpu(reparse_buf->ReparseDataLength) + 8) {
+			cifs_dbg(VFS, "srv returned invalid reparse buf "
+				 "length: %d\n", plen);
 			rc = -EIO;
 			goto querty_exit;
 		}
 
-		/* Do stuff with ioctl_buf/plen */
+		rc = parse_reparse_symlink(
+			(struct reparse_symlink_data_buffer *)reparse_buf,
+			plen, target_path, cifs_sb);
 		goto querty_exit;
 	}
 
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index c7d5813bebd8..31f7c56e0ed8 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -888,6 +888,8 @@  struct file_allocated_range_buffer {
 
 /* struct fsctl_reparse_info_req is empty, only response structs (see below) */
 
+#define REPARSE_TAG_SYMLINK 0xa000000c
+
 struct reparse_data_buffer {
 	__le32	ReparseTag;
 	__le16	ReparseDataLength;
@@ -914,7 +916,19 @@  struct reparse_mount_point_data_buffer {
 	__u8	PathBuffer[0]; /* Variable Length */
 } __packed;
 
-/* See MS-FSCC 2.1.2.4 and cifspdu.h for struct reparse_symlink_data */
+#define SYMLINK_FLAG_RELATIVE 0x00000001
+
+struct reparse_symlink_data_buffer {
+	__le32	ReparseTag;
+	__le16	ReparseDataLength;
+	__u16	Reserved;
+	__le16	SubstituteNameOffset;
+	__le16	SubstituteNameLength;
+	__le16	PrintNameOffset;
+	__le16	PrintNameLength;
+	__le32	Flags;
+	__u8	PathBuffer[0]; /* Variable Length */
+} __packed;
 
 /* See MS-FSCC 2.1.2.6 and cifspdu.h for struct reparse_posix_data */