[PATCH 6.1 0568/1146] stmmac: fix potential division by 0

Greg Kroah-Hartman
2022-12-28T16:13:23Z

From: Piergiorgio Beruto <piergiorgio.beruto@gmail.com>

[ Upstream commit ede5a389852d3640a28e7187fb32b7f204380901 ]

When the MAC is connected to a 10 Mb/s PHY and the PTP clock is derived
from the MAC reference clock (default), the clk_ptp_rate becomes too
small and the calculated sub second increment becomes 0 when computed by
the stmmac_config_sub_second_increment() function within
stmmac_init_tstamp_counter().

Therefore, the subsequent div_u64 in stmmac_init_tstamp_counter()
operation triggers a divide by 0 exception as shown below.

[ 95.062067] socfpga-dwmac ff700000.ethernet eth0: Register MEM_TYPE_PAGE_POOL RxQ-0
[ 95.076440] socfpga-dwmac ff700000.ethernet eth0: PHY [stmmac-0:08] driver [NCN26000] (irq=49)
[ 95.095964] dwmac1000: Master AXI performs any burst length
[ 95.101588] socfpga-dwmac ff700000.ethernet eth0: No Safety Features support found
[ 95.109428] Division by zero in kernel.
[ 95.113447] CPU: 0 PID: 239 Comm: ifconfig Not tainted 6.1.0-rc7-centurion3-1.0.3.0-01574-gb624218205b7-dirty #77
[ 95.123686] Hardware name: Altera SOCFPGA
[ 95.127695] unwind_backtrace from show_stack+0x10/0x14
[ 95.132938] show_stack from dump_stack_lvl+0x40/0x4c
[ 95.137992] dump_stack_lvl from Ldiv0+0x8/0x10
[ 95.142527] Ldiv0 from __aeabi_uidivmod+0x8/0x18
[ 95.147232] __aeabi_uidivmod from div_u64_rem+0x1c/0x40
[ 95.152552] div_u64_rem from stmmac_init_tstamp_counter+0xd0/0x164
[ 95.158826] stmmac_init_tstamp_counter from stmmac_hw_setup+0x430/0xf00
[ 95.165533] stmmac_hw_setup from __stmmac_open+0x214/0x2d4
[ 95.171117] __stmmac_open from stmmac_open+0x30/0x44
[ 95.176182] stmmac_open from __dev_open+0x11c/0x134
[ 95.181172] __dev_open from __dev_change_flags+0x168/0x17c
[ 95.186750] __dev_change_flags from dev_change_flags+0x14/0x50
[ 95.192662] dev_change_flags from devinet_ioctl+0x2b4/0x604
[ 95.198321] devinet_ioctl from inet_ioctl+0x1ec/0x214
[ 95.203462] inet_ioctl from sock_ioctl+0x14c/0x3c4
[ 95.208354] sock_ioctl from vfs_ioctl+0x20/0x38
[ 95.212984] vfs_ioctl from sys_ioctl+0x250/0x844
[ 95.217691] sys_ioctl from ret_fast_syscall+0x0/0x4c
[ 95.222743] Exception stack(0xd0ee1fa8 to 0xd0ee1ff0)
[ 95.227790] 1fa0: 00574c4f be9aeca4 00000003 00008914 be9aeca4 be9aec50
[ 95.235945] 1fc0: 00574c4f be9aeca4 0059f078 00000036 be9aee8c be9aef7a 00000015 00000000
[ 95.244096] 1fe0: 005a01f0 be9aec38 004d7484 b6e67d74

Signed-off-by: Piergiorgio Beruto <piergiorgio.beruto@gmail.com>
Fixes: 91a2559c1dc5 ("net: stmmac: Fix sub-second increment")
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/de4c64ccac9084952c56a06a8171d738604c4770.1670678513.git.piergiorgio.beruto@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c | 3 ++-
drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
index 764832f4dae1..8b50f03056b7 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -47,7 +47,8 @@ static void config_sub_second_increment(void __iomem *ioaddr,
if (!(value & PTP_TCR_TSCTRLSSR))
data = (data * 1000) / 465;

- data &= PTP_SSIR_SSINC_MASK;
+ if (data > PTP_SSIR_SSINC_MAX)
+ data = PTP_SSIR_SSINC_MAX;

reg_value = data;
if (gmac4)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
index 53172a439810..bf619295d079 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
@@ -64,7 +64,7 @@
#define PTP_TCR_TSENMACADDR BIT(18)

/* SSIR defines */
-#define PTP_SSIR_SSINC_MASK 0xff
+#define PTP_SSIR_SSINC_MAX 0xff
#define GMAC4_PTP_SSIR_SSINC_SHIFT 16

/* Auxiliary Control defines */
--
2.35.1