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From 502a0ae30b2c2d53fde16d55fe8ae20312d4b520 Mon Sep 17 00:00:00 2001
From: Davidlohr Bueso <dave@stgolabs.net>
Date: Tue, 18 Aug 2020 09:20:53 -0700
Subject: [PATCH 332/347] net: xfrm: fix compress vs decompress serialization
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz
A crash was seen in xfrm when running ltp's 'tcp4_ipsec06' stresser on v4.x
based RT kernels.
ipcomp_compress() will serialize access to the ipcomp_scratches percpu buffer by
disabling BH and preventing a softirq from coming in and running ipcom_decompress(),
which is never called from process context. This of course won't work on RT and
the buffer can get corrupted; there have been similar issues with in the past with
such assumptions, ie: ebf255ed6c44 (net: add back the missing serialization in
ip_send_unicast_reply()).
Similarly, this patch addresses the issue with locallocks allowing RT to have a
percpu spinlock and do the correct serialization.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
---
net/xfrm/xfrm_ipcomp.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c
index a00ec715aa46..a97997385423 100644
--- a/net/xfrm/xfrm_ipcomp.c
+++ b/net/xfrm/xfrm_ipcomp.c
@@ -20,6 +20,7 @@
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <linux/locallock.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/smp.h>
@@ -36,6 +37,7 @@ struct ipcomp_tfms {
static DEFINE_MUTEX(ipcomp_resource_mutex);
static void * __percpu *ipcomp_scratches;
+static DEFINE_LOCAL_IRQ_LOCK(ipcomp_scratches_lock);
static int ipcomp_scratch_users;
static LIST_HEAD(ipcomp_tfms_list);
@@ -45,12 +47,15 @@ static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
const int plen = skb->len;
int dlen = IPCOMP_SCRATCH_SIZE;
const u8 *start = skb->data;
- const int cpu = get_cpu();
- u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
- struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
- int err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
- int len;
+ u8 *scratch;
+ struct crypto_comp *tfm;
+ int err, len;
+
+ local_lock(ipcomp_scratches_lock);
+ scratch = *this_cpu_ptr(ipcomp_scratches);
+ tfm = *this_cpu_ptr(ipcd->tfms);
+ err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
if (err)
goto out;
@@ -103,7 +108,7 @@ static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
err = 0;
out:
- put_cpu();
+ local_unlock(ipcomp_scratches_lock);
return err;
}
@@ -146,6 +151,8 @@ static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
int err;
local_bh_disable();
+ local_lock(ipcomp_scratches_lock);
+
scratch = *this_cpu_ptr(ipcomp_scratches);
tfm = *this_cpu_ptr(ipcd->tfms);
err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
@@ -158,12 +165,14 @@ static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
}
memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
+ local_unlock(ipcomp_scratches_lock);
local_bh_enable();
pskb_trim(skb, dlen + sizeof(struct ip_comp_hdr));
return 0;
out:
+ local_unlock(ipcomp_scratches_lock);
local_bh_enable();
return err;
}
--
2.36.1
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