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@xxxxxxxxxxxx/ > > Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx> > Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx> > Cc: Wei Liu <wei.liu@xxxxxxxxxx> > Cc: Dexuan Cui <decui@xxxxxxxxxxxxx> > Cc: linux-hyperv@xxxxxxxxxxxxxxx > Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx> > Reported-by: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx> > Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx> > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Applied to hyperv-next. Thanks.
