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Date: Thu, 15 Dec 2022 19:27:59 +0530 From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com> To: Michal Hocko <mhocko@...e.com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, Ben Widawsky <ben.widawsky@...el.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Feng Tang <feng.tang@...el.com>, Andrea Arcangeli <aarcange@...hat.com>, Mel Gorman <mgorman@...hsingularity.net>, Mike Kravetz <mike.kravetz@...cle.com>, Randy Dunlap <rdunlap@...radead.org>, Vlastimil Babka <vbabka@...e.cz>, Andi Kleen <ak@...ux.intel.com>, Dan Williams <dan.j.williams@...el.com>, Huang Ying <ying.huang@...el.com>, linux-api@...r.kernel.org, stable@...r.kernel.org Subject: Re: [RFC PATCH] mm/mempolicy: Fix memory leak in set_mempolicy_home_node system call Michal Hocko <mhocko@...e.com> writes: > On Wed 14-12-22 17:21:10, Mathieu Desnoyers wrote: >> When encountering any vma in the range with policy other than MPOL_BIND >> or MPOL_PREFERRED_MANY, an error is returned without issuing a mpol_put >> on the policy just allocated with mpol_dup(). >> >> This allows arbitrary users to leak kernel memory. >> >> Fixes: c6018b4b2549 ("mm/mempolicy: add set_mempolicy_home_node syscall") >> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com> >> Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com> >> Cc: Ben Widawsky <ben.widawsky@...el.com> >> Cc: Dave Hansen <dave.hansen@...ux.intel.com> >> Cc: Feng Tang <feng.tang@...el.com> >> Cc: Michal Hocko <mhocko@...nel.org> >> Cc: Andrea Arcangeli <aarcange@...hat.com> >> Cc: Mel Gorman <mgorman@...hsingularity.net> >> Cc: Mike Kravetz <mike.kravetz@...cle.com> >> Cc: Randy Dunlap <rdunlap@...radead.org> >> Cc: Vlastimil Babka <vbabka@...e.cz> >> Cc: Andi Kleen <ak@...ux.intel.com> >> Cc: Dan Williams <dan.j.williams@...el.com> >> Cc: Huang Ying <ying.huang@...el.com> >> Cc: <linux-api@...r.kernel.org> >> Cc: Andrew Morton <akpm@...ux-foundation.org> >> Cc: stable@...r.kernel.org # 5.17+ > > Acked-by: Michal Hocko <mhocko@...e.com> > Thanks for catching this! > > Btw. looking at the code again it seems rather pointless to duplicate > the policy just to throw it away anyway. A slightly bigger diff but this > looks more reasonable to me. What do you think? I can also send it as a > clean up on top of your fix. > --- > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 61aa9aedb728..918cdc8a7f0c 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1489,7 +1489,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le > { > struct mm_struct *mm = current->mm; > struct vm_area_struct *vma; > - struct mempolicy *new; > + struct mempolicy *new. *old; > unsigned long vmstart; > unsigned long vmend; > unsigned long end; > @@ -1521,30 +1521,28 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le > return 0; > mmap_write_lock(mm); > for_each_vma_range(vmi, vma, end) { > - vmstart = max(start, vma->vm_start); > - vmend = min(end, vma->vm_end); > - new = mpol_dup(vma_policy(vma)); > - if (IS_ERR(new)) { > - err = PTR_ERR(new); > - break; > - } > - /* > - * Only update home node if there is an existing vma policy > - */ > - if (!new) > - continue; > - > /* > * If any vma in the range got policy other than MPOL_BIND > * or MPOL_PREFERRED_MANY we return error. We don't reset > * the home node for vmas we already updated before. > */ > - if (new->mode != MPOL_BIND && new->mode != MPOL_PREFERRED_MANY) { > + old = vma_policy(vma); > + if (!old) > + continue; > + if (old->mode != MPOL_BIND && old->mode != MPOL_PREFERRED_MANY) { > err = -EOPNOTSUPP; > break; > } > > + new = mpol_dup(vma_policy(vma)); new = mpol_dup(old); > + if (IS_ERR(new)) { > + err = PTR_ERR(new); > + break; > + } > + > new->home_node = home_node; > + vmstart = max(start, vma->vm_start); > + vmend = min(end, vma->vm_end); > err = mbind_range(mm, vmstart, vmend, new); > mpol_put(new); > if (err) > -- > Michal Hocko > SUSE Labs
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