Re: [PATCH] net/ethernet: ks8851_mll fix rx frame buffer overflow

Hi Eric,

On 07:39 Tue 27 Mar     , Eric Dumazet wrote:

Le mardi 27 mars 2012 à 15:01 +0200, Davide Ciminaghi a écrit :

quoted

If interrupts are disabled long enough to allow for more than
32 frames to accumulate in the MAC's internal buffers, a buffer
overflow occurs. This patch fixes the problem by making the
driver's frame_head_info buffer bigger enough.

Signed-off-by: Davide Ciminaghi <redacted>
Signed-off-by: Raffaele Recalcati <redacted>
---
 drivers/net/ethernet/micrel/ks8851_mll.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/net/ethernet/micrel/ks8851_mll.c b/drivers/net/ethernet/micrel/ks8851_mll.c
index 2784bc7..a158e89 100644
--- a/drivers/net/ethernet/micrel/ks8851_mll.c
+++ b/drivers/net/ethernet/micrel/ks8851_mll.c

@@ -40,7 +40,7 @@
 #define	DRV_NAME	"ks8851_mll"
 
 static u8 KS_DEFAULT_MAC_ADDRESS[] = { 0x00, 0x10, 0xA1, 0x86, 0x95, 0x11 };
-#define MAX_RECV_FRAMES			32
+#define MAX_RECV_FRAMES			256
 #define MAX_BUF_SIZE			2048
 #define TX_BUF_SIZE			2000
 #define RX_BUF_SIZE			2000

How can this fix the problem for good ?

You can see in ks_rcv function, 
ks->frame_cnt = ks_rdreg16(ks, KS_RXFCTR) >> 8;
so "RXFC RX Frame Count" is a byte, maximum 256 total frames.
but we have the threshold ..

As you can see also in ks_setup the 
/* Setup Receive Frame Threshold - 1 frame (RXFCTFC) */
ks_wrreg16(ks, KS_RXFCTR, 1 & RXFCTR_THRESHOLD_MASK);

In conclusion what happen is that if we stop system interrupts for a while,
when we are back the ks_rcv function starts reading the frames, and 
the 
while (ks->frame_cnt--) {
..
	frame_hdr++;
}
loop goes out of the malloc'ed area.

We experienced so strange bugs in the last weeks that we are so happy that it seems fixed, but I need
some weeks to confirm it is robust enough.
The 'load setup' is like the following:
- nfs rootfs
- host $ sudo ping -f $TARGET_IP_ADDRESS
- host $ scp -r BIG_DIR user@$TARGET_IP_ADDRESS:
But I'm not sure to create the bug in a mathematical way, it seems to depend on packets on the corporate lan.

Surely if I stop with jtag and restart after some seconds I have buffer overflow, with same errors in ram that I
obtain randomically with 'load setup'.

Hoping it helps,

Raffaele

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