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[Qemu-devel] [PATCH] eepro100: prevent an infinite loop over same comman

From: P J P
Subject: [Qemu-devel] [PATCH] eepro100: prevent an infinite loop over same command block
Date: Fri, 16 Oct 2015 16:42:04 +0530 (IST)


An infinite loop issue in hw/net/eepro100.c emulator was reported by Mr Qinghao Tang(CC'd here).

Below is a proposed fix patch and details about the issue.

From f06497dfefabbdd6f966a5d6c177d85cd0e5ecd8 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <address@hidden>
Date: Fri, 16 Oct 2015 11:33:27 +0530
Subject: eepro100: prevent an infinite loop over same command block

action_command() routine executes a chain of commands located
in the Command Block List(CBL). Each Command Block(CB) has a
link to the next CB in the list, given by 's->tx.link'.
This is used in conjunction with the base address 's->cu_base'.

An infinite loop unfolds if the 'link' to the next CB is
same as the previous one, the loop ends up executing the same
command over and over again.

Reported-by: Qinghao Tang <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
 hw/net/eepro100.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/net/eepro100.c b/hw/net/eepro100.c
index 60333b7..d76d108 100644
--- a/hw/net/eepro100.c
+++ b/hw/net/eepro100.c
@@ -863,6 +863,8 @@ static void action_command(EEPRO100State *s)
         uint16_t ok_status = STATUS_OK;
         s->cb_address = s->cu_base + s->cu_offset;
+        if (s->tx.link == s->cu_offset)
+            break;
         bit_el = ((s->tx.command & COMMAND_EL) != 0);
         bit_s = ((s->tx.command & COMMAND_S) != 0);
         bit_i = ((s->tx.command & COMMAND_I) != 0);

Thank you.
Prasad J Pandit / Red Hat Product Security Team
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F

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