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authorEric Biggers <ebiggers@google.com>2017-11-02 00:47:12 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-11-15 15:53:17 +0100
commit419ec342d312197f0f570a52f237915fb92c8826 (patch)
tree3951fe78b7a12ec0dbaad756d265545aa7133661 /security
parent64a234537a8850aeba8fa65b1bf81d04bc5ae946 (diff)
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KEYS: trusted: fix writing past end of buffer in trusted_read()
commit a3c812f7cfd80cf51e8f5b7034f7418f6beb56c1 upstream. When calling keyctl_read() on a key of type "trusted", if the user-supplied buffer was too small, the kernel ignored the buffer length and just wrote past the end of the buffer, potentially corrupting userspace memory. Fix it by instead returning the size required, as per the documentation for keyctl_read(). We also don't even fill the buffer at all in this case, as this is slightly easier to implement than doing a short read, and either behavior appears to be permitted. It also makes it match the behavior of the "encrypted" key type. Fixes: d00a1c72f7f4 ("keys: add new trusted key-type") Reported-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Mimi Zohar <zohar@linux.vnet.ibm.com> Reviewed-by: James Morris <james.l.morris@oracle.com> Signed-off-by: James Morris <james.l.morris@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'security')
-rw-r--r--security/keys/trusted.c23
1 files changed, 12 insertions, 11 deletions
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 222db148a96b..4ba2f6b91242 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -1147,20 +1147,21 @@ static long trusted_read(const struct key *key, char __user *buffer,
p = rcu_dereference_key(key);
if (!p)
return -EINVAL;
- if (!buffer || buflen <= 0)
- return 2 * p->blob_len;
- ascii_buf = kmalloc(2 * p->blob_len, GFP_KERNEL);
- if (!ascii_buf)
- return -ENOMEM;
- bufp = ascii_buf;
- for (i = 0; i < p->blob_len; i++)
- bufp = hex_byte_pack(bufp, p->blob[i]);
- if ((copy_to_user(buffer, ascii_buf, 2 * p->blob_len)) != 0) {
+ if (buffer && buflen >= 2 * p->blob_len) {
+ ascii_buf = kmalloc(2 * p->blob_len, GFP_KERNEL);
+ if (!ascii_buf)
+ return -ENOMEM;
+
+ bufp = ascii_buf;
+ for (i = 0; i < p->blob_len; i++)
+ bufp = hex_byte_pack(bufp, p->blob[i]);
+ if (copy_to_user(buffer, ascii_buf, 2 * p->blob_len) != 0) {
+ kzfree(ascii_buf);
+ return -EFAULT;
+ }
kzfree(ascii_buf);
- return -EFAULT;
}
- kzfree(ascii_buf);
return 2 * p->blob_len;
}