Re: [PATCH net] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user
On Thu, Oct 05, 2017 at 11:56:44AM +0200, Florian Westphal wrote:
> Eric Dumazet wrote:
> > From: Eric Dumazet
> >
> > 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
> > Cc: Willem de Bruijn
> > ---
> > 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
Applied to nf, thanks.
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Re: [PATCH net] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user
Eric Dumazet wrote:
> From: Eric Dumazet
>
> 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
> Cc: Willem de Bruijn
> ---
> 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
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[PATCH net] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user
From: Eric Dumazet
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
Cc: Willem de Bruijn
---
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;
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