| Message ID | 20220901071210.8402-1-khalid.masum.92@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v4] xfrm: Update ipcomp_scratches with NULL when freed | expand |
On Thu, Sep 01, 2022 at 01:12:10PM +0600, Khalid Masum wrote: > 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 address 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 updating ipcomp_scrtches with NULL when scratches > is freed > > Suggested-by: Herbert Xu <herbert@gondor.apana.org.au> > Reported-by: syzbot+5ec9bb042ddfe9644773@syzkaller.appspotmail.com > Tested-by: syzbot+5ec9bb042ddfe9644773@syzkaller.appspotmail.com > Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Thanks,
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)
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 address 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 updating ipcomp_scrtches with NULL when scratches is freed Suggested-by: Herbert Xu <herbert@gondor.apana.org.au> Reported-by: syzbot+5ec9bb042ddfe9644773@syzkaller.appspotmail.com Tested-by: syzbot+5ec9bb042ddfe9644773@syzkaller.appspotmail.com Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com> --- Changes since v3: - Update ipcomp_scratches to NULL when freed only - Link: https://lore.kernel.org/lkml/20220901040307.4674-1-khalid.masum.92@gmail.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/