| Message ID | 20220927211736.3241175-1-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | fb2d14add4f813c73bd9d28b750315ccb3f5f0ea |
| Headers | show |
| Series | [v2] Drivers: hv: vmbus: Split memcpy of flex-array | expand |
From: Kees Cook <keescook@chromium.org> Sent: Tuesday, September 27, 2022 2:18 PM > > To work around a misbehavior of the compiler's ability to see into > composite flexible array structs (as detailed in the coming memcpy() > hardening series[1]), split the memcpy() of the header and the payload > so no false positive run-time overflow warning will be generated. This > results in the already inlined memcpy getting unrolled a little more, > which very slightly increases text size: > > $ size drivers/hv/vmbus_drv.o.before drivers/hv/vmbus_drv.o > text data bss dec hex filename > 22968 5239 232 28439 6f17 drivers/hv/vmbus_drv.o.before > 23032 5239 232 28503 6f57 drivers/hv/vmbus_drv.o > > Avoids the run-time false-positive warning: > > memcpy: detected field-spanning write (size 212) of single field "&ctx->msg" at > drivers/hv/vmbus_drv.c:1133 (size 16) > > [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org/ > > Cc: "K. Y. Srinivasan" <kys@microsoft.com> > Cc: Haiyang Zhang <haiyangz@microsoft.com> > Cc: Stephen Hemminger <sthemmin@microsoft.com> > Cc: Wei Liu <wei.liu@kernel.org> > Cc: Dexuan Cui <decui@microsoft.com> > Cc: linux-hyperv@vger.kernel.org > Reported-by: Nathan Chancellor <nathan@kernel.org> > Reported-by: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Tested-by: Nathan Chancellor <nathan@kernel.org> > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > v2: - fix commit log, add tags and exact warning test from Nathan > v1: https://lore.kernel.org/lkml/20220924030741.3345349-1-keescook@chromium.org/ > --- > drivers/hv/vmbus_drv.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c > index 23c680d1a0f5..9b111a8262e3 100644 > --- a/drivers/hv/vmbus_drv.c > +++ b/drivers/hv/vmbus_drv.c > @@ -1131,7 +1131,8 @@ void vmbus_on_msg_dpc(unsigned long data) > return; > > INIT_WORK(&ctx->work, vmbus_onmessage_work); > - memcpy(&ctx->msg, &msg_copy, sizeof(msg->header) + payload_size); > + ctx->msg.header = msg_copy.header; > + memcpy(&ctx->msg.payload, msg_copy.u.payload, payload_size); > > /* > * The host can generate a rescind message while we > -- > 2.34.1 Reviewed-by: Michael Kelley <mikelley@microsoft.com>
On Tue, Sep 27, 2022 at 02:17:36PM -0700, Kees Cook wrote: > To work around a misbehavior of the compiler's ability to see into > composite flexible array structs (as detailed in the coming memcpy() > hardening series[1]), split the memcpy() of the header and the payload > so no false positive run-time overflow warning will be generated. This > results in the already inlined memcpy getting unrolled a little more, > which very slightly increases text size: > > $ size drivers/hv/vmbus_drv.o.before drivers/hv/vmbus_drv.o > text data bss dec hex filename > 22968 5239 232 28439 6f17 drivers/hv/vmbus_drv.o.before > 23032 5239 232 28503 6f57 drivers/hv/vmbus_drv.o > > Avoids the run-time false-positive warning: > > memcpy: detected field-spanning write (size 212) of single field "&ctx->msg" at drivers/hv/vmbus_drv.c:1133 (size 16) > > [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org/ > > Cc: "K. Y. Srinivasan" <kys@microsoft.com> > Cc: Haiyang Zhang <haiyangz@microsoft.com> > Cc: Stephen Hemminger <sthemmin@microsoft.com> > Cc: Wei Liu <wei.liu@kernel.org> > Cc: Dexuan Cui <decui@microsoft.com> > Cc: linux-hyperv@vger.kernel.org > Reported-by: Nathan Chancellor <nathan@kernel.org> > Reported-by: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Tested-by: Nathan Chancellor <nathan@kernel.org> > Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> Thanks! -- Gustavo > --- > v2: - fix commit log, add tags and exact warning test from Nathan > v1: https://lore.kernel.org/lkml/20220924030741.3345349-1-keescook@chromium.org > --- > drivers/hv/vmbus_drv.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c > index 23c680d1a0f5..9b111a8262e3 100644 > --- a/drivers/hv/vmbus_drv.c > +++ b/drivers/hv/vmbus_drv.c > @@ -1131,7 +1131,8 @@ void vmbus_on_msg_dpc(unsigned long data) > return; > > INIT_WORK(&ctx->work, vmbus_onmessage_work); > - memcpy(&ctx->msg, &msg_copy, sizeof(msg->header) + payload_size); > + ctx->msg.header = msg_copy.header; > + memcpy(&ctx->msg.payload, msg_copy.u.payload, payload_size); > > /* > * The host can generate a rescind message while we > -- > 2.34.1 >
On Tue, Sep 27, 2022 at 02:17:36PM -0700, Kees Cook wrote: > To work around a misbehavior of the compiler's ability to see into > composite flexible array structs (as detailed in the coming memcpy() > hardening series[1]), split the memcpy() of the header and the payload > so no false positive run-time overflow warning will be generated. This > results in the already inlined memcpy getting unrolled a little more, > which very slightly increases text size: > > $ size drivers/hv/vmbus_drv.o.before drivers/hv/vmbus_drv.o > text data bss dec hex filename > 22968 5239 232 28439 6f17 drivers/hv/vmbus_drv.o.before > 23032 5239 232 28503 6f57 drivers/hv/vmbus_drv.o > > Avoids the run-time false-positive warning: > > memcpy: detected field-spanning write (size 212) of single field "&ctx->msg" at drivers/hv/vmbus_drv.c:1133 (size 16) > > [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org/ > > Cc: "K. Y. Srinivasan" <kys@microsoft.com> > Cc: Haiyang Zhang <haiyangz@microsoft.com> > Cc: Stephen Hemminger <sthemmin@microsoft.com> > Cc: Wei Liu <wei.liu@kernel.org> > Cc: Dexuan Cui <decui@microsoft.com> > Cc: linux-hyperv@vger.kernel.org > Reported-by: Nathan Chancellor <nathan@kernel.org> > Reported-by: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Tested-by: Nathan Chancellor <nathan@kernel.org> > Signed-off-by: Kees Cook <keescook@chromium.org> Applied to hyperv-next. Thanks.
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 23c680d1a0f5..9b111a8262e3 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1131,7 +1131,8 @@ void vmbus_on_msg_dpc(unsigned long data) return; INIT_WORK(&ctx->work, vmbus_onmessage_work); - memcpy(&ctx->msg, &msg_copy, sizeof(msg->header) + payload_size); + ctx->msg.header = msg_copy.header; + memcpy(&ctx->msg.payload, msg_copy.u.payload, payload_size); /* * The host can generate a rescind message while we