Bug in 'git am' when applying a broken patch

Hi all,

I received the patch attached below as part of a submission against the Linux kernel tree. The patch seems to have been hand-edited, and is not correct, and patch verifies this as being a problem:

$ patch -p1 --dry-run < bad_patch.mbox checking file drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c patch: **** malformed patch at line 133: skb_put(skb, sizeof(struct ieee80211_authentication));

But git will actually apply it:
$ git am -s bad_patch.mbox
Applying: staging: rtl8192u: ieee80211: Fix sparse endianness warnings

But, there's nothing in the patch at all except the commit message:

$ git show HEAD
commit f6643dfef5b701db86f23be9ce6fb5b3bafe76b6
Author: Gaston Gonzalez <gascoar@gmail.com>
Date:   Sun May 31 12:17:48 2015 -0300

    staging: rtl8192u: ieee80211: Fix sparse endianness warnings
    
    Fix the following sparse warnings:
    
    drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:663:32: warning: incorrect type in assignment (different base types)
    drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:663:32:    expected restricted __le16 [usertype] frame_ctl
    drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:663:32:    got int
    drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:664:50: warning: invalid assignment: |=
    drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:664:50:    left side has type restricted __le16
    drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c:664:50:    right side has type int
    
    Signed-off-by: Gaston Gonzalez <gascoar@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

$ git diff HEAD^ $

Any ideas what is going on here?  Shouldn't 'git am' have failed?

Oh, I'm using git version 2.4.2 right now.

I've asked Gaston for the original patch to verify before he hand-edited it, to verify that git wasn't creating something wrong here, as well.

thanks,

greg k-h