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Subject[PATCH v4 0/9] bring back stack frame warning with KASAN
This is a new version of patches I originally submitted back in March
[1], and last time in June [2]. This time I have basically rewritten
the entire patch series based on a new approach that came out of GCC
PR81715 that I opened[3]. The upcoming gcc-8 release is now much better
at consolidating stack slots for inline function arguments and would
obsolete most of my workaround patches here, but we still need the
workarounds for gcc-5, gcc-6 and gcc-7. Many thanks to Jakub Jelinek
for the analysis and the gcc-8 patch!

This minimal set of patches only makes sure that we do get frame size
warnings in allmodconfig for x86_64 and arm64 again with a 2048 byte
limit, even with KASAN enabled, but without the new KASAN_EXTRA option.

I set the warning limit with KASAN_EXTRA to 3072, limiting the
allmodconfig+KASAN_EXTRA build output to around 50 legitimate warnings.
These are for stack frames up to 31KB that will cause an immediate stack
overflow, and fixing them would require bringing back my older patches
and more. We can debate whether we want to apply those as a follow-up,
or instead remove the option entirely.

Another follow-up series I have reduces the warning limit with
KASAN to 1536, and without KASAN to 1280 for 64-bit architectures.

I hope we can get all patches merged for v4.14 and most of them
backported into stable kernels. Since we no longer have a dependency
on a preparation patch, my preference would be for the respective
subsystem maintainers to pick up the individual patches.
The last patch introduces a couple of "allmodconfig" build warnings
on x86 and arm64 unless the other patches get merged first, I'll
send that again separately once everything else has been taken
care of.

The remaining contents are:
- -fsanitize-address-use-after-scope is moved to a separate
CONFIG_KASAN_EXTRA option that increases the warning limit
improving compile speed and disabling code that leads to
valid warnings on gcc-7.0.1
- my inline function workaround is applied to netlink, one
ethernet driver and a few media drivers.
- The rework for the brcmsmac driver from previous versions is
still there.

Changes since v3:
- I dropped all "noinline_if_stackbloat" annotations and used
a workaround that introduces additional local variables in the inline
functions to copy the function arguments, resulting in much better
object code at the expense of having rather odd-looking functions.
- The v4 patches now don't help with KASAN_EXTRA any more at all,
is more dangerous in production systems than it was before
- Rewrote the "em28xx" patch to be small enough for a stable backport.
- The rewritten vt-keyboard patches got merged and are now in
stable kernels as well.

Changes since v2:
- rewrote the vt-keyboard patch based on feedback
- and made KMEMCHECK mutually exclusive with KASAN
(rather than KASAN_EXTRA)

Changes since v1:
- dropped patches to fix all the CONFIG_KASAN_EXTRA warnings:
- READ_ONCE/WRITE_ONCE cause problems in lots of code
- typecheck() causes huge problems in a few places
- many more uses of noinline_if_stackbloat



Arnd Bergmann (9):
brcmsmac: make some local variables 'static const' to reduce stack
brcmsmac: split up wlc_phy_workarounds_nphy
brcmsmac: reindent split functions
em28xx: fix em28xx_dvb_init for KASAN
r820t: fix r820t_write_reg for KASAN
dvb-frontends: fix i2c access helpers for KASAN
rocker: fix rocker_tlv_put_* functions for KASAN
netlink: fix nla_put_{u8,u16,u32} for KASAN
kasan: rework Kconfig settings

drivers/media/dvb-frontends/ascot2e.c | 4 +-
drivers/media/dvb-frontends/cxd2841er.c | 4 +-
drivers/media/dvb-frontends/helene.c | 4 +-
drivers/media/dvb-frontends/horus3a.c | 4 +-
drivers/media/dvb-frontends/itd1000.c | 5 +-
drivers/media/dvb-frontends/mt312.c | 4 +-
drivers/media/dvb-frontends/stb0899_drv.c | 3 +-
drivers/media/dvb-frontends/stb6100.c | 6 +-
drivers/media/dvb-frontends/stv0367.c | 4 +-
drivers/media/dvb-frontends/stv090x.c | 4 +-
drivers/media/dvb-frontends/stv6110x.c | 4 +-
drivers/media/dvb-frontends/zl10039.c | 4 +-
drivers/media/tuners/r820t.c | 13 +-
drivers/media/usb/em28xx/em28xx-dvb.c | 30 +-
drivers/net/ethernet/rocker/rocker_tlv.h | 48 +-
.../broadcom/brcm80211/brcmsmac/phy/phy_n.c | 1856 ++++++++++----------
include/net/netlink.h | 73 +-
lib/Kconfig.debug | 4 +-
lib/Kconfig.kasan | 13 +-
lib/Kconfig.kmemcheck | 1 +
scripts/Makefile.kasan | 3 +
21 files changed, 1047 insertions(+), 1044 deletions(-)


Cc: Mauro Carvalho Chehab <>
Cc: Jiri Pirko <>
Cc: Arend van Spriel <>
Cc: Kalle Valo <>
Cc: "David S. Miller" <>
Cc: Andrey Ryabinin <>
Cc: Alexander Potapenko <>
Cc: Dmitry Vyukov <>
Cc: Masahiro Yamada <>
Cc: Michal Marek <>
Cc: Arnd Bergmann <>
Cc: Andrew Morton <>
Cc: Kees Cook <>
Cc: Geert Uytterhoeven <>
Cc: Greg Kroah-Hartman <>
Cc: Jakub Jelinek <>
Cc: Martin Liška <>

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