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Message-Id: <20220831142938.5882-1-khalid.masum.92@gmail.com> Date: Wed, 31 Aug 2022 20:29:38 +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 v2] xfrm: ipcomp: Update ipcomp_scratches with NULL if alloc fails 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; Receiving 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. ... } Fix this breakage by updating ipcomp_scratches with NULL if the above mentioned allocation fails. Reported-and-tested-by: syzbot+5ec9bb042ddfe9644773@...kaller.appspotmail.com Signed-off-by: Khalid Masum <khalid.masum.92@...il.com> --- diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c index cb40ff0ff28d..17815cde8a7f 100644 --- a/net/xfrm/xfrm_ipcomp.c +++ b/net/xfrm/xfrm_ipcomp.c @@ -215,7 +215,7 @@ 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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