[PATCH 4.19 0/3] ipv4/ipv6: backport fixes for CVE-2021-20322

[PATCH 4.19 0/3] ipv4/ipv6: backport fixes for CVE-2021-20322

[Ovidiu Panait]

The following commits are needed to fix CVE-2021-20322:
ipv4:
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6457378fe796815c973f631a1904e147d6ee33b1
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=67d6d681e15b578c1725bad8ad079e05d1c48a8e

ipv6:
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4785305c05b25a242e5314cc821f54ade4c18810
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a00df2caffed3883c341d5685f830434312e4a43

Commit [2] is already present in 4.19 stable, so backport the
remaining three fixes with minor context adjustments.

Eric Dumazet (3):
  ipv4: use siphash instead of Jenkins in fnhe_hashfun()
  ipv6: use siphash in rt6_exception_hash()
  ipv6: make exception cache less predictible

 net/ipv4/route.c | 12 ++++++------
 net/ipv6/route.c | 25 ++++++++++++++++++-------
 2 files changed, 24 insertions(+), 13 deletions(-)

-- 
2.25.1

[PATCH 4.19 1/3] ipv4: use siphash instead of Jenkins in fnhe_hashfun()

[Ovidiu Panait]

From: Eric Dumazet <edumazet@google.com>

commit 6457378fe796815c973f631a1904e147d6ee33b1 upstream.

A group of security researchers brought to our attention
the weakness of hash function used in fnhe_hashfun().

Lets use siphash instead of Jenkins Hash, to considerably
reduce security risks.

Also remove the inline keyword, this really is distracting.

Fixes: d546c621542d ("ipv4: harden fnhe_hashfun()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Keyu Man <kman001@ucr.edu>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
[OP: adjusted context for 4.19 stable]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
---
 net/ipv4/route.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 730a15fc497c..b41d4acc57e6 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -625,14 +625,14 @@ static void fnhe_remove_oldest(struct fnhe_hash_bucket *hash)
 	kfree_rcu(oldest, rcu);
 }
 
-static inline u32 fnhe_hashfun(__be32 daddr)
+static u32 fnhe_hashfun(__be32 daddr)
 {
-	static u32 fnhe_hashrnd __read_mostly;
-	u32 hval;
+	static siphash_key_t fnhe_hash_key __read_mostly;
+	u64 hval;
 
-	net_get_random_once(&fnhe_hashrnd, sizeof(fnhe_hashrnd));
-	hval = jhash_1word((__force u32) daddr, fnhe_hashrnd);
-	return hash_32(hval, FNHE_HASH_SHIFT);
+	net_get_random_once(&fnhe_hash_key, sizeof(fnhe_hash_key));
+	hval = siphash_1u32((__force u32)daddr, &fnhe_hash_key);
+	return hash_64(hval, FNHE_HASH_SHIFT);
 }
 
 static void fill_route_from_fnhe(struct rtable *rt, struct fib_nh_exception *fnhe)
-- 
2.25.1

[PATCH 4.19 2/3] ipv6: use siphash in rt6_exception_hash()

[Ovidiu Panait]

From: Eric Dumazet <edumazet@google.com>

commit 4785305c05b25a242e5314cc821f54ade4c18810 upstream.

A group of security researchers brought to our attention
the weakness of hash function used in rt6_exception_hash()

Lets use siphash instead of Jenkins Hash, to considerably
reduce security risks.

Following patch deals with IPv4.

Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Keyu Man <kman001@ucr.edu>
Cc: Wei Wang <weiwan@google.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Acked-by: Wei Wang <weiwan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[OP: adjusted context for 4.19 stable]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
---
 net/ipv6/route.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f884739a0c1c..9bc806a4ded6 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -45,6 +45,7 @@
 #include <linux/nsproxy.h>
 #include <linux/slab.h>
 #include <linux/jhash.h>
+#include <linux/siphash.h>
 #include <net/net_namespace.h>
 #include <net/snmp.h>
 #include <net/ipv6.h>
@@ -1337,17 +1338,24 @@ static void rt6_exception_remove_oldest(struct rt6_exception_bucket *bucket)
 static u32 rt6_exception_hash(const struct in6_addr *dst,
 			      const struct in6_addr *src)
 {
-	static u32 seed __read_mostly;
-	u32 val;
+	static siphash_key_t rt6_exception_key __read_mostly;
+	struct {
+		struct in6_addr dst;
+		struct in6_addr src;
+	} __aligned(SIPHASH_ALIGNMENT) combined = {
+		.dst = *dst,
+	};
+	u64 val;
 
-	net_get_random_once(&seed, sizeof(seed));
-	val = jhash(dst, sizeof(*dst), seed);
+	net_get_random_once(&rt6_exception_key, sizeof(rt6_exception_key));
 
 #ifdef CONFIG_IPV6_SUBTREES
 	if (src)
-		val = jhash(src, sizeof(*src), val);
+		combined.src = *src;
 #endif
-	return hash_32(val, FIB6_EXCEPTION_BUCKET_SIZE_SHIFT);
+	val = siphash(&combined, sizeof(combined), &rt6_exception_key);
+
+	return hash_64(val, FIB6_EXCEPTION_BUCKET_SIZE_SHIFT);
 }
 
 /* Helper function to find the cached rt in the hash table
-- 
2.25.1

Re: [PATCH 4.19 0/3] ipv4/ipv6: backport fixes for CVE-2021-20322

[Greg KH]

On Thu, Oct 28, 2021 at 10:08:58PM +0300, Ovidiu Panait wrote:
> The following commits are needed to fix CVE-2021-20322:
> ipv4:
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6457378fe796815c973f631a1904e147d6ee33b1
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=67d6d681e15b578c1725bad8ad079e05d1c48a8e
> 
> ipv6:
> [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4785305c05b25a242e5314cc821f54ade4c18810
> [4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a00df2caffed3883c341d5685f830434312e4a43
> 
> Commit [2] is already present in 4.19 stable, so backport the
> remaining three fixes with minor context adjustments.
> 
> Eric Dumazet (3):
>   ipv4: use siphash instead of Jenkins in fnhe_hashfun()
>   ipv6: use siphash in rt6_exception_hash()
>   ipv6: make exception cache less predictible
> 
>  net/ipv4/route.c | 12 ++++++------
>  net/ipv6/route.c | 25 ++++++++++++++++++-------
>  2 files changed, 24 insertions(+), 13 deletions(-)
> 
> -- 
> 2.25.1
> 

You sent 0/3 but only 2 patches showed up?

Can you please resend all 3?

thanks,

greg k-h

[PATCH 4.19 0/3] ipv4/ipv6: backport fixes for CVE-2021-20322

[Ovidiu Panait]

The following commits are needed to fix CVE-2021-20322:
ipv4:
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6457378fe796815c973f631a1904e147d6ee33b1
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=67d6d681e15b578c1725bad8ad079e05d1c48a8e

ipv6:
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4785305c05b25a242e5314cc821f54ade4c18810
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a00df2caffed3883c341d5685f830434312e4a43

Commit [2] is already present in 4.19 stable, so backport the
remaining three fixes with minor context adjustments.

Eric Dumazet (3):
  ipv4: use siphash instead of Jenkins in fnhe_hashfun()
  ipv6: use siphash in rt6_exception_hash()
  ipv6: make exception cache less predictible

 net/ipv4/route.c | 12 ++++++------
 net/ipv6/route.c | 25 ++++++++++++++++++-------
 2 files changed, 24 insertions(+), 13 deletions(-)

-- 
2.25.1

Re: [PATCH 4.19 0/3] ipv4/ipv6: backport fixes for CVE-2021-20322

[Ovidiu Panait]

[-- Attachment #1: Type: text/plain, Size: 2220 bytes --]

Hi Greg,

On 29.10.2021 10:39, Greg KH wrote:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
>
> On Thu, Oct 28, 2021 at 10:08:58PM +0300, Ovidiu Panait wrote:
>> The following commits are needed to fix CVE-2021-20322:
>> ipv4:
>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6457378fe796815c973f631a1904e147d6ee33b1
>> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=67d6d681e15b578c1725bad8ad079e05d1c48a8e
>>
>> ipv6:
>> [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4785305c05b25a242e5314cc821f54ade4c18810
>> [4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a00df2caffed3883c341d5685f830434312e4a43
>>
>> Commit [2] is already present in 4.19 stable, so backport the
>> remaining three fixes with minor context adjustments.
>>
>> Eric Dumazet (3):
>>    ipv4: use siphash instead of Jenkins in fnhe_hashfun()
>>    ipv6: use siphash in rt6_exception_hash()
>>    ipv6: make exception cache less predictible
>>
>>   net/ipv4/route.c | 12 ++++++------
>>   net/ipv6/route.c | 25 ++++++++++++++++++-------
>>   2 files changed, 24 insertions(+), 13 deletions(-)
>>
>> --
>> 2.25.1
>>
> You sent 0/3 but only 2 patches showed up?
>
> Can you please resend all 3?

I tried resending the full patchset, but the last patch is still not 
showing up.

git send-email doesn't report any errors:

OK. Log says:
MAIL FROM:<ovidiu.panait@windriver.com>
RCPT TO:<stable@vger.kernel.org>
RCPT TO:<gregkh@linuxfoundation.org>
From: Ovidiu Panait <ovidiu.panait@windriver.com>
To: stable@vger.kernel.org
Cc: gregkh@linuxfoundation.org
Subject: [PATCH 4.19 3/3] ipv6: make exception cache less predictible
Date: Fri, 29 Oct 2021 10:50:27 +0300
Message-Id: <20211029075027.1910142-4-ovidiu.panait@windriver.com>
X-Mailer: git-send-email 2.25.1
In-Reply-To: <20211029075027.1910142-1-ovidiu.panait@windriver.com>
References: <20211029075027.1910142-1-ovidiu.panait@windriver.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Result: 250


I have attached the 4.19 backport of a00df2caffed ("ipv6: make exception 
cache less predictible").


Ovidiu

> thanks,
>
> greg k-h

[-- Attachment #2: 0003-ipv6-make-exception-cache-less-predictible.patch --]
[-- Type: text/x-patch, Size: 2243 bytes --]

From c9f6f8ebbc70e5cf357f80b77400f0233027b39d Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Sun, 29 Aug 2021 15:16:14 -0700
Subject: [PATCH 4.19 3/3] ipv6: make exception cache less predictible

commit a00df2caffed3883c341d5685f830434312e4a43 upstream.

Even after commit 4785305c05b2 ("ipv6: use siphash in rt6_exception_hash()"),
an attacker can still use brute force to learn some secrets from a victim
linux host.

One way to defeat these attacks is to make the max depth of the hash
table bucket a random value.

Before this patch, each bucket of the hash table used to store exceptions
could contain 6 items under attack.

After the patch, each bucket would contains a random number of items,
between 6 and 10. The attacker can no longer infer secrets.

This is slightly increasing memory size used by the hash table,
we do not expect this to be a problem.

Following patch is dealing with the same issue in IPv4.

Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Keyu Man <kman001@ucr.edu>
Cc: Wei Wang <weiwan@google.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
[OP: adjusted context for 4.19 stable]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
---
 net/ipv6/route.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 9bc806a4ded6..d04f3951c5fb 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1454,6 +1454,7 @@ static int rt6_insert_exception(struct rt6_info *nrt,
 	struct rt6_exception_bucket *bucket;
 	struct in6_addr *src_key = NULL;
 	struct rt6_exception *rt6_ex;
+	int max_depth;
 	int err = 0;
 
 	spin_lock_bh(&rt6_exception_lock);
@@ -1515,7 +1516,9 @@ static int rt6_insert_exception(struct rt6_info *nrt,
 	bucket->depth++;
 	net->ipv6.rt6_stats->fib_rt_cache++;
 
-	if (bucket->depth > FIB6_MAX_DEPTH)
+	/* Randomize max depth to avoid some side channels attacks. */
+	max_depth = FIB6_MAX_DEPTH + prandom_u32_max(FIB6_MAX_DEPTH);
+	while (bucket->depth > max_depth)
 		rt6_exception_remove_oldest(bucket);
 
 out:
-- 
2.25.1

Re: [PATCH 4.19 0/3] ipv4/ipv6: backport fixes for CVE-2021-20322

[Greg KH]

On Fri, Oct 29, 2021 at 11:17:16AM +0300, Ovidiu Panait wrote:
> Hi Greg,
> 
> On 29.10.2021 10:39, Greg KH wrote:
> > [Please note: This e-mail is from an EXTERNAL e-mail address]
> > 
> > On Thu, Oct 28, 2021 at 10:08:58PM +0300, Ovidiu Panait wrote:
> > > The following commits are needed to fix CVE-2021-20322:
> > > ipv4:
> > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6457378fe796815c973f631a1904e147d6ee33b1
> > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=67d6d681e15b578c1725bad8ad079e05d1c48a8e
> > > 
> > > ipv6:
> > > [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4785305c05b25a242e5314cc821f54ade4c18810
> > > [4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a00df2caffed3883c341d5685f830434312e4a43
> > > 
> > > Commit [2] is already present in 4.19 stable, so backport the
> > > remaining three fixes with minor context adjustments.
> > > 
> > > Eric Dumazet (3):
> > >    ipv4: use siphash instead of Jenkins in fnhe_hashfun()
> > >    ipv6: use siphash in rt6_exception_hash()
> > >    ipv6: make exception cache less predictible
> > > 
> > >   net/ipv4/route.c | 12 ++++++------
> > >   net/ipv6/route.c | 25 ++++++++++++++++++-------
> > >   2 files changed, 24 insertions(+), 13 deletions(-)
> > > 
> > > --
> > > 2.25.1
> > > 
> > You sent 0/3 but only 2 patches showed up?
> > 
> > Can you please resend all 3?
> 
> I tried resending the full patchset, but the last patch is still not showing
> up.
> 
> git send-email doesn't report any errors:
> 
> OK. Log says:
> MAIL FROM:<ovidiu.panait@windriver.com>
> RCPT TO:<stable@vger.kernel.org>
> RCPT TO:<gregkh@linuxfoundation.org>
> From: Ovidiu Panait <ovidiu.panait@windriver.com>
> To: stable@vger.kernel.org
> Cc: gregkh@linuxfoundation.org
> Subject: [PATCH 4.19 3/3] ipv6: make exception cache less predictible
> Date: Fri, 29 Oct 2021 10:50:27 +0300
> Message-Id: <20211029075027.1910142-4-ovidiu.panait@windriver.com>
> X-Mailer: git-send-email 2.25.1
> In-Reply-To: <20211029075027.1910142-1-ovidiu.panait@windriver.com>
> References: <20211029075027.1910142-1-ovidiu.panait@windriver.com>
> MIME-Version: 1.0
> Content-Transfer-Encoding: 8bit
> 
> Result: 250
> 
> 
> I have attached the 4.19 backport of a00df2caffed ("ipv6: make exception
> cache less predictible").

Odd, it did not come to me either.  I've taken the attached file, thanks.

greg k-h