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CIFS: Fix a possible invalid memory access in smb2_query_symlink()

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During following a symbolic link we received err_buf from SMB2_open().
While the validity of SMB2 error response is checked previously
in smb2_check_message() a symbolic link payload is not checked at all.
Fix it by adding such checks.

Cc: Dan Carpenter <dan.carpenter@oracle.com>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>
This commit is contained in:
Pavel Shilovsky 2016-07-24 10:37:38 +03:00 committed by Steve French
parent a6b5058faf
commit 7893242e24
1 changed files with 29 additions and 1 deletions
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30
fs/cifs/smb2ops.c
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@ -1044,6 +1044,9 @@ smb2_new_lease_key(struct cifs_fid *fid)
get_random_bytes(fid->lease_key, SMB2_LEASE_KEY_SIZE);
}
#define SMB2_SYMLINK_STRUCT_SIZE \
(sizeof(struct smb2_err_rsp) - 1 + sizeof(struct smb2_symlink_err_rsp))
static int
smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
const char *full_path, char **target_path,
@ -1056,7 +1059,10 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
struct cifs_fid fid;
struct smb2_err_rsp *err_buf = NULL;
struct smb2_symlink_err_rsp *symlink;
unsigned int sub_len, sub_offset;
unsigned int sub_len;
unsigned int sub_offset;
unsigned int print_len;
unsigned int print_offset;
cifs_dbg(FYI, "%s: path: %s\n", __func__, full_path);
@ -1077,11 +1083,33 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
kfree(utf16_path);
return -ENOENT;
}
if (le32_to_cpu(err_buf->ByteCount) < sizeof(struct smb2_symlink_err_rsp) ||
get_rfc1002_length(err_buf) + 4 < SMB2_SYMLINK_STRUCT_SIZE) {
kfree(utf16_path);
return -ENOENT;
}
/* open must fail on symlink - reset rc */
rc = 0;
symlink = (struct smb2_symlink_err_rsp *)err_buf->ErrorData;
sub_len = le16_to_cpu(symlink->SubstituteNameLength);
sub_offset = le16_to_cpu(symlink->SubstituteNameOffset);
print_len = le16_to_cpu(symlink->PrintNameLength);
print_offset = le16_to_cpu(symlink->PrintNameOffset);
if (get_rfc1002_length(err_buf) + 4 <
SMB2_SYMLINK_STRUCT_SIZE + sub_offset + sub_len) {
kfree(utf16_path);
return -ENOENT;
}
if (get_rfc1002_length(err_buf) + 4 <
SMB2_SYMLINK_STRUCT_SIZE + print_offset + print_len) {
kfree(utf16_path);
return -ENOENT;
}
*target_path = cifs_strndup_from_utf16(
(char *)symlink->PathBuffer + sub_offset,
sub_len, true, cifs_sb->local_nls);