| Message ID | 20220901040307.4674-1-khalid.masum.92@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v3] xfrm: Update ipcomp_scratches with NULL if not allocated | expand |
On Thu, Sep 01, 2022 at 10:03:07AM +0600, Khalid Masum wrote: > > 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; > } Good catch! This is probably the root cause of all the crashes. > 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; This is unnecessary as with your first hunk, ipcomp_scratches is guaranteed to be NULL. Thanks,
On Thu, Sep 1, 2022 at 10:18 AM Herbert Xu <herbert@gondor.apana.org.au> wrote: > > On Thu, Sep 01, 2022 at 10:03:07AM +0600, Khalid Masum wrote: > > > > 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; > > } > > Good catch! This is probably the root cause of all the crashes. > > > 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; > > This is unnecessary as with your first hunk, ipcomp_scratches > is guaranteed to be NULL. > > Thanks, > -- You are right. Instead of setting it to NULL at both places, it makes more sense to do it when memory is freed. I shall send a v4 with the suggested change. thanks, -- Khalid Masum
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;
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@syzkaller.appspotmail.com Tested-by: syzbot+5ec9bb042ddfe9644773@syzkaller.appspotmail.com Signed-off-by: Khalid Masum <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/