Re: [PATCH net v1] drivers/net/bonding: Fix out-of-bounds read in bond_option_arp_ip_targets_set()

[Hangbin Liu <liuhangbin@gmail.com>]

On Mon, Apr 15, 2024 at 11:40:31AM +0800, Sam Sun wrote:
> 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.
> 
> Reported-by: Yue Sun <samsun1006219@gmail.com>

Not sure if there is a need to add Reported-by yourself if you are the author.

Also you need a Fixes tag if the patch target is net tree.

> Signed-off-by: Yue Sun <samsun1006219@gmail.com>
> ---
>  drivers/net/bonding/bond_options.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/bonding/bond_options.c
> b/drivers/net/bonding/bond_options.c
> index 4cdbc7e084f4..db8d99ca1de0 100644
> --- a/drivers/net/bonding/bond_options.c
> +++ b/drivers/net/bonding/bond_options.c
> @@ -1214,7 +1214,8 @@ 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)) {
> +        if (!(strlen(newval->string)) ||
> +            !in4_pton(newval->string + 1, -1, (u8 *)&target, -1, NULL)) {
>              netdev_err(bond->dev, "invalid ARP target %pI4 specified\n",
>                     &target);

Do we need to init target first if !(strlen(newval->string)) ?

Thanks
Hangbin
>              return ret;
> -- 
> 2.34.1