I apologize for recognizing the email in the TOP POST format. I missed the comment in the previous email. 2023년 4월 27일 (목) 오후 6:52, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>님이 작성: > > On Thu, Apr 27, 2023 at 06:29:16PM +0900, sangsup lee wrote: > > Is there any comment for this issue? > > What issue? > > > (reference: https://www.spinics.net/lists/kernel/msg4731408.html) > > Please use lore.kernel.org links, we have no control over any other > random email archive . > > And the above link just points to this proposed patch. > > > > > > > 2023년 3월 23일 (목) 오전 10:37, Sangsup Lee <k1rh4.lee@xxxxxxxxx>님이 작성: > > > > > > From: Sangsup lee <k1rh4.lee@xxxxxxxxx> > > > > > > This patch adds mutex_lock for fixing an Use-after-free bug. > > > fastrpc_req_munmap_impl can be called concurrently in multi-threded environments. > > > The buf which is allocated by list_for_each_safe can be used after another thread frees it. > > How was this tested? > I was unable to configure the environment in which this code is running. Therefore, I could not go through dynamic testing for the related issue. However, I found vulnerabilities in similar types of functions in other drivers in the mobile environment, so I think this code is also problematic. > > > > > > Signed-off-by: Sangsup lee <k1rh4.lee@xxxxxxxxx> > > > --- > > > V1 -> V2: moving the locking to ioctl. > > > > > > drivers/misc/fastrpc.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c > > > index 93ebd174d848..aa1cf0e9f4ed 100644 > > > --- a/drivers/misc/fastrpc.c > > > +++ b/drivers/misc/fastrpc.c > > > @@ -1901,7 +1901,9 @@ static long fastrpc_device_ioctl(struct file *file, unsigned int cmd, > > > err = fastrpc_req_mmap(fl, argp); > > > break; > > > case FASTRPC_IOCTL_MUNMAP: > > > + mutex_lock(&fl->mutex); > > > err = fastrpc_req_munmap(fl, argp); > > > + mutex_unlock(&fl->mutex); > > Are you sure you can call this function with the lock? If so, why isn't > the mmap ioctl also locked? I am convinced that FASTRPC_IOCTL_MUNMAP can lead to a race condition bug. However, as I mentioned in patch v1, I am not an expert in fastrpc. I worried about the side effects of the code I suggested. So, I asked you to recommend which code to use, and this is the code that was recommended to me. And I didn't check the mmap function because I couldn't find a bug in mmap. > > thanks, > > greg k-h
