On Wed, Jan 08, 2025 at 10:18:02AM +0530, Ling Xu wrote: > fastrpc_req_munmap involves two steps to unmap memory, first to locates > a matching fastrpc buf in the list and second is to send request to DSP > to unmap. There is a potential race condition between two operations > which can lead to user-after-free scenario. > Lock unmap request to avoid use-after-free. > > Signed-off-by: Ling Xu <quic_lxu5@xxxxxxxxxxx> > --- > drivers/misc/fastrpc.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c > index 7b7a22c91fe4..9ad092d3a705 100644 > --- a/drivers/misc/fastrpc.c > +++ b/drivers/misc/fastrpc.c > @@ -2117,7 +2117,9 @@ 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); Why do you grab a mutex here when this function grabs the spinlock too? This feels like an odd fix, shouldn't the lock be in the function at the very least? thanks, greg k-h
