netdev - Re: [PATCH net v1] drivers/net/bonding: Fix out-of-bounds read in bond_option_arp_ip_targets

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Date: Mon, 15 Apr 2024 16:46:24 +0800
From: Sam Sun <samsun1006219@...il.com>
To: Hangbin Liu <liuhangbin@...il.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, j.vosburgh@...il.com, 
	andy@...yhouse.net, davem@...emloft.net, Eric Dumazet <edumazet@...gle.com>, 
	kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH net v1] drivers/net/bonding: Fix out-of-bounds read in bond_option_arp_ip_targets_set()

On Mon, Apr 15, 2024 at 3:32 PM Hangbin Liu <liuhangbin@...il.com> wrote:
>
> 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@...il.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.

Sorry for missing the Fixes tag, I will add it to patch. I am also not
sure if I should add Reported-by here, since it's my first time to
commit a patch for linux.

> > Signed-off-by: Yue Sun <samsun1006219@...il.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)) ?
>
Good question. I think we don't need to init target first, since in
original logic in4_pton() also leave target untouched if any error
occurs. If !(strlen(newval->string)), bond_option_arp_ip_targets_set()
just ret and target is still untouched. But I am not sure about it.

If anyone finds other problems, please let me know.

Thanks,
Yue
> Thanks
> Hangbin
> >              return ret;
> > --
> > 2.34.1