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Date: Mon, 18 May 2020 09:06:59 +0800 From: Jeremy Kerr <jk@...abs.org> To: Finn Thain <fthain@...egraphics.com.au>, "David S. Miller" <davem@...emloft.net> Cc: Paul Mackerras <paulus@...ba.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Stan Johnson <userm57@...oo.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org> Subject: Re: [PATCH] net: bmac: Fix stack corruption panic in bmac_probe() Hi Finn, > This fixes an old bug recently revealed by CONFIG_STACKPROTECTOR. Good catch. I'm not sure about the fix though. That variable ('addr') should be a ethernet hardware address; I'm surprised we're accessing past the 6th byte. The culprit seems to be this, where 'ea' is the address buffer: static void bmac_get_station_address(struct net_device *dev, unsigned char *ea) { int i; unsigned short data; for (i = 0; i < 6; i++) { reset_and_select_srom(dev); data = read_srom(dev, i + EnetAddressOffset/2, SROMAddressBits); ea[2*i] = bitrev8(data & 0x0ff); ea[2*i+1] = bitrev8((data >> 8) & 0x0ff); } } - where it looks like the condition on that for-loop is wrong; we're reading two bytes at a time there. Can you try the attached patch? Ben/Paul - any thoughts? Cheers, Jeremy ----- >From 141b20bcbdb3ad7c166b83b4ea61f3521d0a0679 Mon Sep 17 00:00:00 2001 From: Jeremy Kerr <jk@...abs.org> Date: Mon, 18 May 2020 08:54:25 +0800 Subject: [PATCH] net: bmac: Fix read of MAC address from ROM In bmac_get_station_address, We're reading two bytes at a time from ROM, but we do that six times, resulting in 12 bytes of read & writes. This means we will write off the end of the six-byte destination buffer. This change fixes the for-loop to only read/write six bytes. Based on a proposed fix from Finn Thain <fthain@...egraphics.com.au>. Signed-off-by: Jeremy Kerr <jk@...abs.org> Reported-by: Stan Johnson <userm57@...oo.com> Reported-by: Finn Thain <fthain@...egraphics.com.au> --- drivers/net/ethernet/apple/bmac.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/apple/bmac.c b/drivers/net/ethernet/apple/bmac.c index a58185b1d8bf..3e3711b60d01 100644 --- a/drivers/net/ethernet/apple/bmac.c +++ b/drivers/net/ethernet/apple/bmac.c @@ -1182,7 +1182,7 @@ bmac_get_station_address(struct net_device *dev, unsigned char *ea) int i; unsigned short data; - for (i = 0; i < 6; i++) + for (i = 0; i < 3; i++) { reset_and_select_srom(dev); data = read_srom(dev, i + EnetAddressOffset/2, SROMAddressBits); -- 2.17.1
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