commit 3239b6f29bdfb4b0a2ba59df995fc9e6f4df7f1f
author Eric Biggers <ebiggers@google.com> Thu Nov 02 00:47:03 2017 +0000
committer James Morris <james.l.morris@oracle.com> Thu Nov 02 20:58:05 2017 +1100
tree aaca6a6994664d8c704b49fd3cc7f995e75007a8
parent 3a99df9a3d14cd866b5516f8cba515a3bfd554ab

KEYS: return full count in keyring_read() if buffer is too small

Commit e645016abc80 ("KEYS: fix writing past end of user-supplied buffer
in keyring_read()") made keyring_read() stop corrupting userspace memory
when the user-supplied buffer is too small.  However it also made the
return value in that case be the short buffer size rather than the size
required, yet keyctl_read() is actually documented to return the size
required.  Therefore, switch it over to the documented behavior.

Note that for now we continue to have it fill the short buffer, since it
did that before (pre-v3.13) and dump_key_tree_aux() in keyutils arguably
relies on it.

Fixes: e645016abc80 ("KEYS: fix writing past end of user-supplied buffer in keyring_read()")
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Cc: <stable@vger.kernel.org> # v3.13+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>