| Message ID | 20240614114602.3187710-1-carsten.haitzler@foss.arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm: Fix alignment of temporary stack ioctl buffers | expand |
On Fri, Jun 14, 2024 at 4:47 AM <carsten.haitzler@foss.arm.com> wrote: > > From: Carsten Haitzler <carsten.haitzler@foss.arm.com> > > In a few places (core drm + AMD kfd driver), the ioctl handling uses a > temporary 128 byte buffer on the stack to copy to/from user. ioctl data > can have structs with types of much larger sizes than a byte and a > system may require alignment of types in these. At the same time the > compiler may align a char buf to something else as it has no idea that > this buffer is used for storing structs with such alignment > requirements. At a minimum putting in alignment information as an > attribute should be a warning in future if an architecture that needs > more alignment appears. > > This was discovered while implementing capability ABI support in Linux > on ARM's Morello CPU (128 bit capability "pointers" in userspace, with > a 64bit non-capability kernel (hybrid) setup). In this, userspace > ioctl structs now had to transport capabilities that needed 16 byte > alignment, but the kernel was not putting these data buffers on that > alignment boundary. > > Currently the largest type that is needed is a u64 so the alignment > only asks for that. > > Signed-off-by: Carsten Haitzler <carsten.haitzler@foss.arm.com> Reviewed-by: T.J. Mercier <tjmercier@google.com> > --- > drivers/dma-buf/dma-heap.c | 2 +- > drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 2 +- > drivers/gpu/drm/drm_ioctl.c | 2 +- > 3 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c > index 84ae708fafe7..8fa68b8a9b60 100644 > --- a/drivers/dma-buf/dma-heap.c > +++ b/drivers/dma-buf/dma-heap.c > @@ -126,7 +126,7 @@ static unsigned int dma_heap_ioctl_cmds[] = { > static long dma_heap_ioctl(struct file *file, unsigned int ucmd, > unsigned long arg) > { > - char stack_kdata[128]; > + _Alignas(u64) char stack_kdata[128]; > char *kdata = stack_kdata; > unsigned int kcmd; > unsigned int in_size, out_size, drv_size, ksize; > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c > index fdf171ad4a3c..201a5c0227ec 100644 > --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c > @@ -3236,7 +3236,7 @@ static long kfd_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) > amdkfd_ioctl_t *func; > const struct amdkfd_ioctl_desc *ioctl = NULL; > unsigned int nr = _IOC_NR(cmd); > - char stack_kdata[128]; > + _Alignas(u64) char stack_kdata[128]; > char *kdata = NULL; > unsigned int usize, asize; > int retcode = -EINVAL; > diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c > index e368fc084c77..77a88b597c0b 100644 > --- a/drivers/gpu/drm/drm_ioctl.c > +++ b/drivers/gpu/drm/drm_ioctl.c > @@ -767,7 +767,7 @@ long drm_ioctl(struct file *filp, > drm_ioctl_t *func; > unsigned int nr = DRM_IOCTL_NR(cmd); > int retcode = -EINVAL; > - char stack_kdata[128]; > + _Alignas(u64) char stack_kdata[128]; > char *kdata = NULL; > unsigned int in_size, out_size, drv_size, ksize; > bool is_driver_ioctl; > -- > 2.25.1 >
diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c index 84ae708fafe7..8fa68b8a9b60 100644 --- a/drivers/dma-buf/dma-heap.c +++ b/drivers/dma-buf/dma-heap.c @@ -126,7 +126,7 @@ static unsigned int dma_heap_ioctl_cmds[] = { static long dma_heap_ioctl(struct file *file, unsigned int ucmd, unsigned long arg) { - char stack_kdata[128]; + _Alignas(u64) char stack_kdata[128]; char *kdata = stack_kdata; unsigned int kcmd; unsigned int in_size, out_size, drv_size, ksize; diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c index fdf171ad4a3c..201a5c0227ec 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c @@ -3236,7 +3236,7 @@ static long kfd_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) amdkfd_ioctl_t *func; const struct amdkfd_ioctl_desc *ioctl = NULL; unsigned int nr = _IOC_NR(cmd); - char stack_kdata[128]; + _Alignas(u64) char stack_kdata[128]; char *kdata = NULL; unsigned int usize, asize; int retcode = -EINVAL; diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index e368fc084c77..77a88b597c0b 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -767,7 +767,7 @@ long drm_ioctl(struct file *filp, drm_ioctl_t *func; unsigned int nr = DRM_IOCTL_NR(cmd); int retcode = -EINVAL; - char stack_kdata[128]; + _Alignas(u64) char stack_kdata[128]; char *kdata = NULL; unsigned int in_size, out_size, drv_size, ksize; bool is_driver_ioctl;