Em Tue, 8 Jan 2019 10:58:34 +0200 Sakari Ailus <[email protected]> escreveu:
> PAGE_ALIGN() may wrap the buffer size around to 0. Prevent this by > checking that the aligned value is not smaller than the unaligned one. > > Note on backporting to stable: the file used to be under > drivers/media/v4l2-core, it was moved to the current location after 4.14. > > Signed-off-by: Sakari Ailus <[email protected]> > Cc: [email protected] > Reviewed-by: Hans Verkuil <[email protected]> > --- > drivers/media/common/videobuf2/videobuf2-core.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/media/common/videobuf2/videobuf2-core.c > b/drivers/media/common/videobuf2/videobuf2-core.c > index 0ca81d495bda..0234ddbfa4de 100644 > --- a/drivers/media/common/videobuf2/videobuf2-core.c > +++ b/drivers/media/common/videobuf2/videobuf2-core.c > @@ -207,6 +207,10 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb) > for (plane = 0; plane < vb->num_planes; ++plane) { > unsigned long size = PAGE_ALIGN(vb->planes[plane].length); > > + /* Did it wrap around? */ > + if (size < vb->planes[plane].length) > + goto free; > + Sorry, but I can't see how this could ever happen (except for a very serious bug at the compiler or at the hardware). See, the definition at PAGE_ALIGN is (from mm.h): #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE) and the macro it uses come from kernel.h: #define __ALIGN_KERNEL(x, a) __ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1) #define __ALIGN_KERNEL_MASK(x, mask) (((x) + (mask)) & ~(mask)) .. #define ALIGN(x, a) __ALIGN_KERNEL((x), (a)) So, this: size = PAGE_ALIGN(length); (assuming PAGE_SIZE= 0x1000) becomes: size = (length + 0x0fff) & ~0xfff; so, size will *always* be >= length. Thanks, Mauro
