linux-kernel - [PATCH 3/3] kasan: increase 32-bit stack frame warning limit

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Date:   Wed,  3 Jul 2019 22:54:38 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Abbott Liu <liuwenliang@...wei.com>,
        linux-arm-kernel@...ts.infradead.org, kasan-dev@...glegroups.com,
        Linus Walleij <linus.walleij@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] kasan: increase 32-bit stack frame warning limit

Enabling kasan on 32-bit ARM introduces some new warnings in the
allmodconfig build due to mildly increased kernel stack usage, even when
asan-stack is disabled:

fs/select.c:621:5: error: stack frame size of 1032 bytes in function 'core_sys_select'
net/mac80211/mlme.c:4047:6: error: stack frame size of 1032 bytes in function 'ieee80211_sta_rx_queued_mgmt'
drivers/infiniband/sw/rxe/rxe_req.c:583:5: error: stack frame size of 1152 bytes in function 'rxe_requester'
fs/ubifs/replay.c:1193:5: error: stack frame size of 1152 bytes in function 'ubifs_replay_journal'
drivers/mtd/chips/cfi_cmdset_0001.c:1868:12: error: stack frame size of 1104 bytes in function 'cfi_intelext_writev'
drivers/ntb/hw/idt/ntb_hw_idt.c:1041:27: error: stack frame size of 1032 bytes in function 'idt_scan_mws'
drivers/mtd/nftlcore.c:674:12: error: stack frame size of 1120 bytes in function 'nftl_writeblock'
drivers/net/wireless/cisco/airo.c:3793:12: error: stack frame size of 1040 bytes in function 'setup_card'
drivers/staging/fbtft/fbtft-core.c:989:5: error: stack frame size of 1232 bytes in function 'fbtft_init_display'
drivers/staging/fbtft/fbtft-core.c:907:12: error: stack frame size of 1072 bytes in function 'fbtft_init_display_dt'
drivers/staging/wlan-ng/cfg80211.c:272:12: error: stack frame size of 1040 bytes in function 'prism2_scan'

Some of these are intentionally high, others are from sloppy coding
practice and should perhaps be reduced a lot.

For 64-bit, the limit is currently much higher at 2048 bytes, which
does not cause many warnings and could even be reduced. Changing the
limit to 1280 bytes with KASAN also takes care of all cases I see.
If we go beyond that with KASAN, or over the normal 1024 byte limit
without it, that is however something we should definitely address
in the code.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 lib/Kconfig.debug | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 6d2799190fba..41b0ae9d05d9 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -251,7 +251,7 @@ config FRAME_WARN
 	int "Warn for stack frames larger than (needs gcc 4.4)"
 	range 0 8192
 	default 2048 if GCC_PLUGIN_LATENT_ENTROPY
-	default 1280 if (!64BIT && PARISC)
+	default 1280 if (!64BIT && (PARISC || KASAN))
 	default 1024 if (!64BIT && !PARISC)
 	default 2048 if 64BIT
 	help
-- 
2.20.0