| Message ID | 20220831014126.6708-1-khalid.masum.92@gmail.com (mailing list archive) |
|---|---|
| State | Awaiting Upstream |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | xfrm: Don't increase scratch users if allocation fails | expand |
On Wed, Aug 31, 2022 at 07:41:26AM +0600, Khalid Masum wrote: > ipcomp_alloc_scratches() routine increases ipcomp_scratch_users count > even if it fails to allocate memory. Therefore, ipcomp_free_scratches() > routine, when triggered, tries to vfree() non existent percpu > ipcomp_scratches. > > To fix this breakage, do not increase scratch users count if > ipcomp_alloc_scratches() fails to allocate scratches. > > Reported-and-tested-by: syzbot+5ec9bb042ddfe9644773@syzkaller.appspotmail.com > Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com> > --- > net/xfrm/xfrm_ipcomp.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c > index cb40ff0ff28d..af9097983139 100644 > --- a/net/xfrm/xfrm_ipcomp.c > +++ b/net/xfrm/xfrm_ipcomp.c > @@ -210,13 +210,15 @@ static void * __percpu *ipcomp_alloc_scratches(void) > void * __percpu *scratches; > int i; > > - if (ipcomp_scratch_users++) > + if (ipcomp_scratch_users) { > + ipcomp_scratch_users++; > return ipcomp_scratches; > - > + } > scratches = alloc_percpu(void *); > if (!scratches) > return NULL; > > + ipcomp_scratch_users++; > ipcomp_scratches = scratches; This patch is broken because on error we will always call ipcomp_free_scratches which frees any partially allocated memory and restores ipcomp_scratch_users to zero. With this patch ipcomp_scratch_users will turn negative on error. Cheers,
On 8/31/22 15:13, Herbert Xu wrote: > On Wed, Aug 31, 2022 at 07:41:26AM +0600, Khalid Masum wrote: >> ipcomp_alloc_scratches() routine increases ipcomp_scratch_users count >> even if it fails to allocate memory. Therefore, ipcomp_free_scratches() >> routine, when triggered, tries to vfree() non existent percpu >> ipcomp_scratches. >> >> To fix this breakage, do not increase scratch users count if >> ipcomp_alloc_scratches() fails to allocate scratches. >> >> Reported-and-tested-by: syzbot+5ec9bb042ddfe9644773@syzkaller.appspotmail.com >> Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com> >> --- >> net/xfrm/xfrm_ipcomp.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c >> index cb40ff0ff28d..af9097983139 100644 >> --- a/net/xfrm/xfrm_ipcomp.c >> +++ b/net/xfrm/xfrm_ipcomp.c >> @@ -210,13 +210,15 @@ static void * __percpu *ipcomp_alloc_scratches(void) >> void * __percpu *scratches; >> int i; >> >> - if (ipcomp_scratch_users++) >> + if (ipcomp_scratch_users) { >> + ipcomp_scratch_users++; >> return ipcomp_scratches; >> - >> + } >> scratches = alloc_percpu(void *); >> if (!scratches) >> return NULL; >> >> + ipcomp_scratch_users++; >> ipcomp_scratches = scratches; > > This patch is broken because on error we will always call > ipcomp_free_scratches which frees any partially allocated memory > and restores ipcomp_scratch_users to zero. > > With this patch ipcomp_scratch_users will turn negative on error. > > Cheers, Thanks for the review. I think it can be fixed by assigning NULL in ipcomp_scratches when the allocation fails as ipcomp_free_scratches checks for it. I shall follow this email with a v2 shortly. thanks, -- Khalid Masum
diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c index cb40ff0ff28d..af9097983139 100644 --- a/net/xfrm/xfrm_ipcomp.c +++ b/net/xfrm/xfrm_ipcomp.c @@ -210,13 +210,15 @@ static void * __percpu *ipcomp_alloc_scratches(void) void * __percpu *scratches; int i; - if (ipcomp_scratch_users++) + if (ipcomp_scratch_users) { + ipcomp_scratch_users++; return ipcomp_scratches; - + } scratches = alloc_percpu(void *); if (!scratches) return NULL; + ipcomp_scratch_users++; ipcomp_scratches = scratches; for_each_possible_cpu(i) {
ipcomp_alloc_scratches() routine increases ipcomp_scratch_users count even if it fails to allocate memory. Therefore, ipcomp_free_scratches() routine, when triggered, tries to vfree() non existent percpu ipcomp_scratches. To fix this breakage, do not increase scratch users count if ipcomp_alloc_scratches() fails to allocate scratches. Reported-and-tested-by: syzbot+5ec9bb042ddfe9644773@syzkaller.appspotmail.com Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com> --- net/xfrm/xfrm_ipcomp.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)