From b3f2d07f4649adcf6905953a10d217b5683e4077 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Fri, 3 Feb 2017 17:35:46 +0100 Subject: [PATCH] hns: avoid stack overflow with CONFIG_KASAN The use of ACCESS_ONCE() looks like a micro-optimization to force gcc to use an indexed load for the register address, but it has an absolutely detrimental effect on builds with gcc-5 and CONFIG_KASAN=y, leading to a very likely kernel stack overflow aside from very complex object code: hisilicon/hns/hns_dsaf_gmac.c: In function 'hns_gmac_update_stats': hisilicon/hns/hns_dsaf_gmac.c:419:1: error: the frame size of 2912 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_ppe.c: In function 'hns_ppe_reset_common': hisilicon/hns/hns_dsaf_ppe.c:390:1: error: the frame size of 1184 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_ppe.c: In function 'hns_ppe_get_regs': hisilicon/hns/hns_dsaf_ppe.c:621:1: error: the frame size of 3632 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_rcb.c: In function 'hns_rcb_get_common_regs': hisilicon/hns/hns_dsaf_rcb.c:970:1: error: the frame size of 2784 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_gmac.c: In function 'hns_gmac_get_regs': hisilicon/hns/hns_dsaf_gmac.c:641:1: error: the frame size of 5728 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_rcb.c: In function 'hns_rcb_get_ring_regs': hisilicon/hns/hns_dsaf_rcb.c:1021:1: error: the frame size of 2208 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_main.c: In function 'hns_dsaf_comm_init': hisilicon/hns/hns_dsaf_main.c:1209:1: error: the frame size of 1904 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_xgmac.c: In function 'hns_xgmac_get_regs': hisilicon/hns/hns_dsaf_xgmac.c:748:1: error: the frame size of 4704 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_main.c: In function 'hns_dsaf_update_stats': hisilicon/hns/hns_dsaf_main.c:2420:1: error: the frame size of 1088 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] hisilicon/hns/hns_dsaf_main.c: In function 'hns_dsaf_get_regs': hisilicon/hns/hns_dsaf_main.c:2753:1: error: the frame size of 10768 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] This does not seem to happen any more with gcc-7, but removing the ACCESS_ONCE seems safe anyway and it avoids a serious issue for some people. I have verified that with gcc-5.3.1, the object code we get is better in the new version both with and without CONFIG_KASAN, as we no longer allocate a 1344 byte stack frame for hns_dsaf_get_regs() but otherwise have practically identical object code. With gcc-7.0.0, removing ACCESS_ONCE has no effect, the object code is already good either way. This patch is probably not urgent to get into 4.11 as only KASAN=y builds with certain compilers are affected, but I still think it makes sense to backport into older kernels. Cc: stable@vger.kernel.org Fixes: 511e6bc ("net: add Hisilicon Network Subsystem DSAF support") Signed-off-by: Arnd Bergmann Signed-off-by: David S. Miller --- drivers/net/ethernet/hisilicon/hns/hns_dsaf_reg.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/hisilicon/hns/hns_dsaf_reg.h b/drivers/net/ethernet/hisilicon/hns/hns_dsaf_reg.h index 87226685f742..8fa18fc17cd2 100644 --- a/drivers/net/ethernet/hisilicon/hns/hns_dsaf_reg.h +++ b/drivers/net/ethernet/hisilicon/hns/hns_dsaf_reg.h @@ -1014,9 +1014,7 @@ static inline void dsaf_write_reg(void __iomem *base, u32 reg, u32 value) { - u8 __iomem *reg_addr = ACCESS_ONCE(base); - - writel(value, reg_addr + reg); + writel(value, base + reg); } #define dsaf_write_dev(a, reg, value) \ @@ -1024,9 +1022,7 @@ static inline void dsaf_write_reg(void __iomem *base, u32 reg, u32 value) static inline u32 dsaf_read_reg(u8 __iomem *base, u32 reg) { - u8 __iomem *reg_addr = ACCESS_ONCE(base); - - return readl(reg_addr + reg); + return readl(base + reg); } static inline void dsaf_write_syscon(struct regmap *base, u32 reg, u32 value) -- 2.11.0