Re: [PATCH net] bonding: fix out-of-bounds read of arp_ip_target

[Jay Vosburgh <jv@jvosburgh.net>]

Jiayuan Chen <jiayuan.chen@linux.dev> wrote:

>arp_ip_target is a module parameter array with BOND_MAX_ARP_TARGETS
>entries. In the loop parsing it in bond_check_params(), arp_ip_count is
>the number of accepted targets, while i is the index into
>arp_ip_target. Invalid and duplicate entries are skipped without
>bumping arp_ip_count, so bounding the loop with arp_ip_count lets i run
>past the end of arp_ip_target, e.g. 16 targets with one duplicate:
>
>  BUG: KASAN: global-out-of-bounds in bond_check_params.constprop.0+0x1148/0x1440
>  Read of size 8 at addr ffffffff96e9ee00 by task swapper/0/1
>  Call Trace:
>   <TASK>
>   dump_stack_lvl+0x91/0xf0
>   print_report+0xd1/0x630
>   kasan_report+0xf3/0x130
>   __asan_report_load8_noabort+0x14/0x30
>   bond_check_params.constprop.0+0x1148/0x1440
>   bonding_init+0x13/0xe0
>   do_one_initcall+0xe7/0x5b0
>   kernel_init_freeable+0xa91/0x1120
>   kernel_init+0x24/0x220
>   ret_from_fork+0x5b3/0x820
>   ret_from_fork_asm+0x1a/0x30
>   </TASK>
>
>  The buggy address belongs to the variable:
>   arp_ip_target+0x80/0xa0
>
>Bound the loop with i instead. arp_ip_count never exceeds i, so it
>stays within BOND_MAX_ARP_TARGETS too.
>
>Fixes: 5a5c5fd48e3b ("bonding: arp_ip_count and arp_targets can be wrong")
>Cc: stable@vger.kernel.org
>Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>

Acked-by: Jay Vosburgh <jv@jvosburgh.net>


>---
> drivers/net/bonding/bond_main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 09aa45d71fab..7019e5d8fdc8 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -6273,7 +6273,7 @@ static int __init bond_check_params(struct bond_params *params)
> 	}
> 
> 	for (arp_ip_count = 0, i = 0;
>-	     (arp_ip_count < BOND_MAX_ARP_TARGETS) && arp_ip_target[i]; i++) {
>+	     (i < BOND_MAX_ARP_TARGETS) && arp_ip_target[i]; i++) {
> 		__be32 ip;
> 
> 		/* not a complete check, but good enough to catch mistakes */
>-- 
>2.43.0
>