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Message-Id: <20220901040307.4674-1-khalid.masum.92@gmail.com>
Date: Thu, 1 Sep 2022 10:03:07 +0600
From: Khalid Masum <khalid.masum.92@...il.com>
To: Herbert Xu <herbert@...dor.apana.org.au>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Cc: Steffen Klassert <steffen.klassert@...unet.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
linux-kernel-mentees@...ts.linuxfoundation.org,
Shuah Khan <skhan@...uxfoundation.org>,
syzbot+5ec9bb042ddfe9644773@...kaller.appspotmail.com,
Khalid Masum <khalid.masum.92@...il.com>
Subject: [PATCH v3] xfrm: Update ipcomp_scratches with NULL if not allocated
Currently if ipcomp_alloc_scratches() fails to allocate memory
ipcomp_scratches holds obsolete address. So when we try to free the
percpu scratches using ipcomp_free_scratches() it tries to vfree non
existent vm area. Described below:
static void * __percpu *ipcomp_alloc_scratches(void)
{
...
scratches = alloc_percpu(void *);
if (!scratches)
return NULL;
ipcomp_scratches does not know about this allocation failure.
Therefore holding the old obsolete address.
...
}
So when we free,
static void ipcomp_free_scratches(void)
{
...
scratches = ipcomp_scratches;
Assigning obsolete addresses from ipcomp_scratches
if (!scratches)
return;
for_each_possible_cpu(i)
vfree(*per_cpu_ptr(scratches, i));
Trying to free non existent page, causing warning: trying to vfree
existent vm area.
...
}
Fix this breakage by:
(1) Update ipcomp_scratches with NULL if the above mentioned
allocation fails.
(2) Update ipcomp_scrtches with NULL when scratches is freed
Reported-by: syzbot+5ec9bb042ddfe9644773@...kaller.appspotmail.com
Tested-by: syzbot+5ec9bb042ddfe9644773@...kaller.appspotmail.com
Signed-off-by: Khalid Masum <khalid.masum.92@...il.com>
---
Changes since v2:
- Set ipcomp_scratches to NULL when scratches is freed.
- Update commit message.
- v2 Link: https://lore.kernel.org/lkml/20220831142938.5882-1-khalid.masum.92@gmail.com/
Changes since v1:
- Instead of altering usercount, update ipcomp_scratches to NULL
- Update commit message.
- v1 Link: https://lore.kernel.org/lkml/20220831014126.6708-1-khalid.masum.92@gmail.com/
diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c
index cb40ff0ff28d..3774d07c5819 100644
--- a/net/xfrm/xfrm_ipcomp.c
+++ b/net/xfrm/xfrm_ipcomp.c
@@ -203,6 +203,7 @@ static void ipcomp_free_scratches(void)
vfree(*per_cpu_ptr(scratches, i));
free_percpu(scratches);
+ ipcomp_scratches = NULL;
}
static void * __percpu *ipcomp_alloc_scratches(void)
@@ -215,7 +216,7 @@ static void * __percpu *ipcomp_alloc_scratches(void)
scratches = alloc_percpu(void *);
if (!scratches)
- return NULL;
+ return ipcomp_scratches = NULL;
ipcomp_scratches = scratches;
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