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authorEric Biggers <ebiggers@google.com>2017-11-02 03:47:12 +0300
committerJames Morris <james.l.morris@oracle.com>2017-11-02 12:58:07 +0300
commita3c812f7cfd80cf51e8f5b7034f7418f6beb56c1 (patch)
treea242e63ebea632ce64f1745703f43c0357b0c594
parent3239b6f29bdfb4b0a2ba59df995fc9e6f4df7f1f (diff)
downloadlinux-a3c812f7cfd80cf51e8f5b7034f7418f6beb56c1.tar.xz
KEYS: trusted: fix writing past end of buffer in trusted_read()
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> Cc: <stable@vger.kernel.org> # v2.6.38+ 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>
-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 bd85315cbfeb..98aa89ff7bfd 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 = dereference_key_locked(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;
}