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cifs: extra sanity checking for cifs.idmap keys 

Now that we aren't so rigid about the length of the key being passed
in, we need to be a bit more rigorous about checking the length of
the actual data against the claimed length (a'la num_subauths field).

Check for the case where userspace sends us a seemingly valid key
with a num_subauths field that goes beyond the end of the array. If
that happens, return -EIO and invalidate the key.

Also change the other places where we check for malformed keys in this
code to invalidate the key as well.

Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
This commit is contained in:
Jeff Layton 2012-12-03 06:05:30 -05:00 committed by Steve French
parent 41a9f1f6b3
commit 2ae03025d5
1 changed files with 18 additions and 2 deletions
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20
fs/cifs/cifsacl.c
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@ -191,6 +191,8 @@ id_to_sid(unsigned int cid, uint sidtype, struct cifs_sid *ssid)
{
int rc;
struct key *sidkey;
struct cifs_sid *ksid;
unsigned int ksid_size;
char desc[3 + 10 + 1]; /* 3 byte prefix + 10 bytes for value + NULL */
const struct cred *saved_cred;
@ -211,14 +213,27 @@ id_to_sid(unsigned int cid, uint sidtype, struct cifs_sid *ssid)
rc = -EIO;
cFYI(1, "%s: Downcall contained malformed key "
"(datalen=%hu)", __func__, sidkey->datalen);
goto out_key_put;
goto invalidate_key;
}
cifs_copy_sid(ssid, (struct cifs_sid *)sidkey->payload.data);
ksid = (struct cifs_sid *)sidkey->payload.data;
ksid_size = CIFS_SID_BASE_SIZE + (ksid->num_subauth * sizeof(__le32));
if (ksid_size > sidkey->datalen) {
rc = -EIO;
cFYI(1, "%s: Downcall contained malformed key (datalen=%hu, "
"ksid_size=%u)", __func__, sidkey->datalen, ksid_size);
goto invalidate_key;
}
cifs_copy_sid(ssid, ksid);
out_key_put:
key_put(sidkey);
out_revert_creds:
revert_creds(saved_cred);
return rc;
invalidate_key:
key_invalidate(sidkey);
goto out_key_put;
}
static int
@ -264,6 +279,7 @@ sid_to_id(struct cifs_sb_info *cifs_sb, struct cifs_sid *psid,
rc = -EIO;
cFYI(1, "%s: Downcall contained malformed key "
"(datalen=%hu)", __func__, sidkey->datalen);
key_invalidate(sidkey);
goto out_key_put;
}