netdev - Re: [PATCH net v4] bonding: Fix out-of-bounds read in bond_option_arp_ip_targets

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Message-ID: <ZiJpfZQb_yA936Wh@Laptop-X1>
Date: Fri, 19 Apr 2024 20:54:21 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: 'Simon Horman' <horms@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jay Vosburgh <j.vosburgh@...il.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Ding Tianhong <dingtianhong@...wei.com>,
	Sam Sun <samsun1006219@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net v4] bonding: Fix out-of-bounds read in
 bond_option_arp_ip_targets_set()

On Fri, Apr 19, 2024 at 12:08:25PM +0100, 'Simon Horman' wrote:
> From: Sam Sun <samsun1006219@...il.com>
> 
> In function bond_option_arp_ip_targets_set(), if newval->string is an
> empty string, newval->string+1 will point to the byte after the
> string, causing an out-of-bound read.
> 
> BUG: KASAN: slab-out-of-bounds in strlen+0x7d/0xa0 lib/string.c:418
> Read of size 1 at addr ffff8881119c4781 by task syz-executor665/8107
> CPU: 1 PID: 8107 Comm: syz-executor665 Not tainted 6.7.0-rc7 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
>  print_address_description mm/kasan/report.c:364 [inline]
>  print_report+0xc1/0x5e0 mm/kasan/report.c:475
>  kasan_report+0xbe/0xf0 mm/kasan/report.c:588
>  strlen+0x7d/0xa0 lib/string.c:418
>  __fortify_strlen include/linux/fortify-string.h:210 [inline]
>  in4_pton+0xa3/0x3f0 net/core/utils.c:130
>  bond_option_arp_ip_targets_set+0xc2/0x910
> drivers/net/bonding/bond_options.c:1201
>  __bond_opt_set+0x2a4/0x1030 drivers/net/bonding/bond_options.c:767
>  __bond_opt_set_notify+0x48/0x150 drivers/net/bonding/bond_options.c:792
>  bond_opt_tryset_rtnl+0xda/0x160 drivers/net/bonding/bond_options.c:817
>  bonding_sysfs_store_option+0xa1/0x120 drivers/net/bonding/bond_sysfs.c:156
>  dev_attr_store+0x54/0x80 drivers/base/core.c:2366
>  sysfs_kf_write+0x114/0x170 fs/sysfs/file.c:136
>  kernfs_fop_write_iter+0x337/0x500 fs/kernfs/file.c:334
>  call_write_iter include/linux/fs.h:2020 [inline]
>  new_sync_write fs/read_write.c:491 [inline]
>  vfs_write+0x96a/0xd80 fs/read_write.c:584
>  ksys_write+0x122/0x250 fs/read_write.c:637
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
> ---[ end trace ]---
> 
> Fix it by adding a check of string length before using it.
> 
> Fixes: f9de11a16594 ("bonding: add ip checks when store ip target")
> Signed-off-by: Yue Sun <samsun1006219@...il.com>
> Signed-off-by: Simon Horman <horms@...nel.org>
> ---
> Changes in v4 (Simon):
> - Correct  whitespace mangled patch; posting as requested by Sam Sun
> - Link to v3: https://lore.kernel.org/r/CAEkJfYOnsLLiCrtgOpq2Upr+_W0dViYVHU8YdjJOi-mxD8H9oQ@mail.gmail.com
> 
> Changes in v3 (Sam Sun):
> - According to Hangbin's opinion, change Fixes tag from 4fb0ef585eb2
>   ("bonding: convert arp_ip_target to use the new option API") to
>   f9de11a16594 ("bonding: add ip checks when store ip target").
> - Link to v2: https://lore.kernel.org/r/CAEkJfYMdDQKY1C-wBZLiaJ=dCqfM9r=rykwwf+J-XHsFp7D9Ag@mail.gmail.com/
> 
> Changes in v2 (Sam Sun):
> - According to Jay and Hangbin's opinion, remove target address in
>   netdev_err message since target is not initialized in error path and
>   will not provide useful information.
> - Link to v1: https://lore.kernel.org/r/CAEkJfYPYF-nNB2oiXfXwjPG0VVB2Bd8Q8kAq+74J=R+4HkngWw@mail.gmail.com/
> ---
>  drivers/net/bonding/bond_options.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
> index 0cacd7027e35..64a06e3399ee 100644
> --- a/drivers/net/bonding/bond_options.c
> +++ b/drivers/net/bonding/bond_options.c
> @@ -1214,9 +1214,9 @@ static int bond_option_arp_ip_targets_set(struct bonding *bond,
>  	__be32 target;
>  
>  	if (newval->string) {
> -		if (!in4_pton(newval->string+1, -1, (u8 *)&target, -1, NULL)) {
> -			netdev_err(bond->dev, "invalid ARP target %pI4 specified\n",
> -				   &target);
> +		if (!(strlen(newval->string)) ||
> +		    !in4_pton(newval->string + 1, -1, (u8 *)&target, -1, NULL)) {
> +			netdev_err(bond->dev, "invalid ARP target I4 specified\n");

Hi Simon, the error message should be "invalid ARP target specified\n"

Thanks
Hangbin