| Message ID | 20210318134334.2933141-2-arnd@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/2] media: v4l2-core: ignore native time32 ioctls on 64-bit | expand |
Hi Arnd, Thank you for the patch. On Thu, Mar 18, 2021 at 02:43:19PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > As seen from a recent syzbot bug report, mistakes in the compat ioctl > implementation can lead to uninitialized kernel stack data getting used > as input for driver ioctl handlers. > > The reported bug is now fixed, but it's possible that other related > bugs are still present or get added in the future. As the drivers need > to check user input already, the possible impact is fairly low, but it > might still cause an information leak. > > To be on the safe side, always clear the entire ioctl buffer before > calling the conversion handler functions that are meant to initialize > them. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > --- > drivers/media/v4l2-core/v4l2-ioctl.c | 51 ++++++++++++++++------------ > 1 file changed, 29 insertions(+), 22 deletions(-) > > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c > index 2b1bb68dc27f..6cec92d0972c 100644 > --- a/drivers/media/v4l2-core/v4l2-ioctl.c > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c > @@ -3164,12 +3164,23 @@ static int video_get_user(void __user *arg, void *parg, > > if (cmd == real_cmd) { > if (copy_from_user(parg, (void __user *)arg, n)) > - err = -EFAULT; > - } else if (in_compat_syscall()) { > - err = v4l2_compat_get_user(arg, parg, cmd); > - } else { > - switch (cmd) { > + return -EFAULT; > + > + /* zero out anything we don't copy from userspace */ > + if (n < _IOC_SIZE(real_cmd)) > + memset((u8 *)parg + n, 0, _IOC_SIZE(real_cmd) - n); > + > + return 0; > + } > + > + /* zero out whole buffer first to deal with missing emulation */ > + memset(parg, 0, _IOC_SIZE(real_cmd)); > + > + if (in_compat_syscall()) > + return v4l2_compat_get_user(arg, parg, cmd); > + > #if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) > + switch (cmd) { > case VIDIOC_QUERYBUF_TIME32: > case VIDIOC_QBUF_TIME32: > case VIDIOC_DQBUF_TIME32: > @@ -3182,28 +3193,24 @@ static int video_get_user(void __user *arg, void *parg, > > *vb = (struct v4l2_buffer) { > .index = vb32.index, > - .type = vb32.type, > - .bytesused = vb32.bytesused, > - .flags = vb32.flags, > - .field = vb32.field, > - .timestamp.tv_sec = vb32.timestamp.tv_sec, > - .timestamp.tv_usec = vb32.timestamp.tv_usec, > - .timecode = vb32.timecode, > - .sequence = vb32.sequence, > - .memory = vb32.memory, > - .m.userptr = vb32.m.userptr, > - .length = vb32.length, > - .request_fd = vb32.request_fd, > + .type = vb32.type, > + .bytesused = vb32.bytesused, > + .flags = vb32.flags, > + .field = vb32.field, > + .timestamp.tv_sec = vb32.timestamp.tv_sec, > + .timestamp.tv_usec = vb32.timestamp.tv_usec, > + .timecode = vb32.timecode, > + .sequence = vb32.sequence, > + .memory = vb32.memory, > + .m.userptr = vb32.m.userptr, > + .length = vb32.length, > + .request_fd = vb32.request_fd, > }; > break; > } > -#endif > - } > } > +#endif > > - /* zero out anything we don't copy from userspace */ > - if (!err && n < _IOC_SIZE(real_cmd)) > - memset((u8 *)parg + n, 0, _IOC_SIZE(real_cmd) - n); > return err; > } > -- Regards, Laurent Pinchart
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c index 2b1bb68dc27f..6cec92d0972c 100644 --- a/drivers/media/v4l2-core/v4l2-ioctl.c +++ b/drivers/media/v4l2-core/v4l2-ioctl.c @@ -3164,12 +3164,23 @@ static int video_get_user(void __user *arg, void *parg, if (cmd == real_cmd) { if (copy_from_user(parg, (void __user *)arg, n)) - err = -EFAULT; - } else if (in_compat_syscall()) { - err = v4l2_compat_get_user(arg, parg, cmd); - } else { - switch (cmd) { + return -EFAULT; + + /* zero out anything we don't copy from userspace */ + if (n < _IOC_SIZE(real_cmd)) + memset((u8 *)parg + n, 0, _IOC_SIZE(real_cmd) - n); + + return 0; + } + + /* zero out whole buffer first to deal with missing emulation */ + memset(parg, 0, _IOC_SIZE(real_cmd)); + + if (in_compat_syscall()) + return v4l2_compat_get_user(arg, parg, cmd); + #if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) + switch (cmd) { case VIDIOC_QUERYBUF_TIME32: case VIDIOC_QBUF_TIME32: case VIDIOC_DQBUF_TIME32: @@ -3182,28 +3193,24 @@ static int video_get_user(void __user *arg, void *parg, *vb = (struct v4l2_buffer) { .index = vb32.index, - .type = vb32.type, - .bytesused = vb32.bytesused, - .flags = vb32.flags, - .field = vb32.field, - .timestamp.tv_sec = vb32.timestamp.tv_sec, - .timestamp.tv_usec = vb32.timestamp.tv_usec, - .timecode = vb32.timecode, - .sequence = vb32.sequence, - .memory = vb32.memory, - .m.userptr = vb32.m.userptr, - .length = vb32.length, - .request_fd = vb32.request_fd, + .type = vb32.type, + .bytesused = vb32.bytesused, + .flags = vb32.flags, + .field = vb32.field, + .timestamp.tv_sec = vb32.timestamp.tv_sec, + .timestamp.tv_usec = vb32.timestamp.tv_usec, + .timecode = vb32.timecode, + .sequence = vb32.sequence, + .memory = vb32.memory, + .m.userptr = vb32.m.userptr, + .length = vb32.length, + .request_fd = vb32.request_fd, }; break; } -#endif - } } +#endif - /* zero out anything we don't copy from userspace */ - if (!err && n < _IOC_SIZE(real_cmd)) - memset((u8 *)parg + n, 0, _IOC_SIZE(real_cmd) - n); return err; }