* [PATCH net] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user
@ 2017-10-05 9:50 Eric Dumazet
2017-10-05 9:56 ` Florian Westphal
0 siblings, 1 reply; 3+ messages in thread
From: Eric Dumazet @ 2017-10-05 9:50 UTC (permalink / raw)
To: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal
Cc: netfilter-devel, netdev, Willem de Bruijn, netdev
From: Eric Dumazet <edumazet@google.com>
syzkaller reports an out of bound read in strlcpy(), triggered
by xt_copy_counters_from_user()
Fix this by using memcpy(), then forcing a zero byte at the last position
of the destination, as Florian did for the non COMPAT code.
Fixes: d7591f0c41ce ("netfilter: x_tables: introduce and use xt_copy_counters_from_user")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
---
net/netfilter/x_tables.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index c83a3b5e1c6c2a91b713b6681a794bd79ab3fa08..d8571f4142080a3c121fc90f0b52d81ee9df6712 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -892,7 +892,7 @@ void *xt_copy_counters_from_user(const void __user *user, unsigned int len,
if (copy_from_user(&compat_tmp, user, sizeof(compat_tmp)) != 0)
return ERR_PTR(-EFAULT);
- strlcpy(info->name, compat_tmp.name, sizeof(info->name));
+ memcpy(info->name, compat_tmp.name, sizeof(info->name) - 1);
info->num_counters = compat_tmp.num_counters;
user += sizeof(compat_tmp);
} else
@@ -905,9 +905,9 @@ void *xt_copy_counters_from_user(const void __user *user, unsigned int len,
if (copy_from_user(info, user, sizeof(*info)) != 0)
return ERR_PTR(-EFAULT);
- info->name[sizeof(info->name) - 1] = '\0';
user += sizeof(*info);
}
+ info->name[sizeof(info->name) - 1] = '\0';
size = sizeof(struct xt_counters);
size *= info->num_counters;
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH net] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user
2017-10-05 9:50 [PATCH net] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user Eric Dumazet
@ 2017-10-05 9:56 ` Florian Westphal
2017-10-06 13:05 ` Pablo Neira Ayuso
0 siblings, 1 reply; 3+ messages in thread
From: Florian Westphal @ 2017-10-05 9:56 UTC (permalink / raw)
To: Eric Dumazet
Cc: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal,
netfilter-devel, netdev, Willem de Bruijn
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> From: Eric Dumazet <edumazet@google.com>
>
> syzkaller reports an out of bound read in strlcpy(), triggered
> by xt_copy_counters_from_user()
>
> Fix this by using memcpy(), then forcing a zero byte at the last position
> of the destination, as Florian did for the non COMPAT code.
>
> Fixes: d7591f0c41ce ("netfilter: x_tables: introduce and use xt_copy_counters_from_user")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Willem de Bruijn <willemb@google.com>
> ---
> net/netfilter/x_tables.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> index c83a3b5e1c6c2a91b713b6681a794bd79ab3fa08..d8571f4142080a3c121fc90f0b52d81ee9df6712 100644
> --- a/net/netfilter/x_tables.c
> +++ b/net/netfilter/x_tables.c
> @@ -892,7 +892,7 @@ void *xt_copy_counters_from_user(const void __user *user, unsigned int len,
> if (copy_from_user(&compat_tmp, user, sizeof(compat_tmp)) != 0)
> return ERR_PTR(-EFAULT);
>
> - strlcpy(info->name, compat_tmp.name, sizeof(info->name));
> + memcpy(info->name, compat_tmp.name, sizeof(info->name) - 1);
Argh, right, compat_tmp.name might not be 0 terminated :-/
Acked-by: Florian Westphal <fw@strlen.de>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH net] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user
2017-10-05 9:56 ` Florian Westphal
@ 2017-10-06 13:05 ` Pablo Neira Ayuso
0 siblings, 0 replies; 3+ messages in thread
From: Pablo Neira Ayuso @ 2017-10-06 13:05 UTC (permalink / raw)
To: Florian Westphal
Cc: Eric Dumazet, Jozsef Kadlecsik, netfilter-devel, netdev,
Willem de Bruijn
On Thu, Oct 05, 2017 at 11:56:44AM +0200, Florian Westphal wrote:
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > From: Eric Dumazet <edumazet@google.com>
> >
> > syzkaller reports an out of bound read in strlcpy(), triggered
> > by xt_copy_counters_from_user()
> >
> > Fix this by using memcpy(), then forcing a zero byte at the last position
> > of the destination, as Florian did for the non COMPAT code.
> >
> > Fixes: d7591f0c41ce ("netfilter: x_tables: introduce and use xt_copy_counters_from_user")
> > Signed-off-by: Eric Dumazet <edumazet@google.com>
> > Cc: Willem de Bruijn <willemb@google.com>
> > ---
> > net/netfilter/x_tables.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> > index c83a3b5e1c6c2a91b713b6681a794bd79ab3fa08..d8571f4142080a3c121fc90f0b52d81ee9df6712 100644
> > --- a/net/netfilter/x_tables.c
> > +++ b/net/netfilter/x_tables.c
> > @@ -892,7 +892,7 @@ void *xt_copy_counters_from_user(const void __user *user, unsigned int len,
> > if (copy_from_user(&compat_tmp, user, sizeof(compat_tmp)) != 0)
> > return ERR_PTR(-EFAULT);
> >
> > - strlcpy(info->name, compat_tmp.name, sizeof(info->name));
> > + memcpy(info->name, compat_tmp.name, sizeof(info->name) - 1);
>
> Argh, right, compat_tmp.name might not be 0 terminated :-/
>
> Acked-by: Florian Westphal <fw@strlen.de>
Applied to nf, thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-10-05 9:50 [PATCH net] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user Eric Dumazet
2017-10-05 9:56 ` Florian Westphal
2017-10-06 13:05 ` Pablo Neira Ayuso
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