Commit 6d66e093 authored by Mohsin Bashir's avatar Mohsin Bashir Committed by Jakub Kicinski
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eth: fbnic: Fix counter roll-over issue 



Fix a potential counter roll-over issue in fbnic_mbx_alloc_rx_msgs()
when calculating descriptor slots. The issue occurs when head - tail
results in a large positive value (unsigned) and the compiler interprets
head - tail - 1 as a signed value.

Since FBNIC_IPC_MBX_DESC_LEN is a power of two, use a masking operation,
which is a common way of avoiding this problem when dealing with these
sort of ring space calculations.

Fixes: da3cde08 ("eth: fbnic: Add FW communication mechanism")
Signed-off-by: default avatarMohsin Bashir <mohsin.bashr@gmail.com>
Link: https://patch.msgid.link/20251125211704.3222413-1-mohsin.bashr@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 27fd0286

drivers/net/ethernet/meta/fbnic/fbnic_fw.c

+1 −1
Original line number Diff line number Diff line
@@ -201,7 +201,7 @@ static int fbnic_mbx_alloc_rx_msgs(struct fbnic_dev *fbd) 
		return -ENODEV;



	/* Fill all but 1 unused descriptors in the Rx queue. */

	count = (head - tail - 1) % FBNIC_IPC_MBX_DESC_LEN;

	count = (head - tail - 1) & (FBNIC_IPC_MBX_DESC_LEN - 1);

	while (!err && count--) {

		struct fbnic_tlv_msg *msg;