Messages in this thread | | | Date | Wed, 14 Dec 2022 18:38:17 +0530 | Subject | Re: usb: f_fs: Fix CFI failure in ki_complete | From | Prashanth K <> |
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On 12-12-22 07:05 pm, Greg Kroah-Hartman wrote: > On Mon, Dec 12, 2022 at 06:54:24PM +0530, Prashanth K wrote: >> Function pointer ki_complete() expects 'long' as its second >> argument, but we pass integer from ffs_user_copy_worker. This >> might cause a CFI failure, as ki_complete is an indirect call >> with mismatched prototype. Fix this by typecasting the second >> argument to long. > > "might"? Does it or not? If it does, why hasn't this been reported > before? Sorry for the confusion in commit text, We caught a CFI (Control Flow Integrity) failure internally on 5.15, hence pushed this patch. But later I came to know that CFI was implemented on 5.4 kernel for Android. Will push the same on ACK and share the related details there.
Thanks. > >> Cc: <stable@vger.kernel.org> # 5.15 > > CFI first showed up in 6.1, not 5.15, right? > >> Signed-off-by: Prashanth K <quic_prashk@quicinc.com> >> >> --- >> drivers/usb/gadget/function/f_fs.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c >> index 73dc10a7..9c26561 100644 >> --- a/drivers/usb/gadget/function/f_fs.c >> +++ b/drivers/usb/gadget/function/f_fs.c >> @@ -835,7 +835,7 @@ static void ffs_user_copy_worker(struct work_struct *work) >> kthread_unuse_mm(io_data->mm); >> } >> >> - io_data->kiocb->ki_complete(io_data->kiocb, ret); >> + io_data->kiocb->ki_complete(io_data->kiocb, (long)ret); > > Why just fix up this one instance? What about ep_user_copy_worker()? > And what about all other calls to ki_complete that are not using a > (long) cast? > > This feels wrong, what exactly is the reported error and how come other > kernel calls to this function pointer have not had a problem with CFI? > ceph_aio_complete() would be another example, right? > > thanks, > > greg k-h
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