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.

[ Mathieu: compile-tested only. Tested-by would be welcome. ]

Fixes: c6018b4b2549 ("mm/mempolicy: add set_mempolicy_home_node syscall") Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Reviewed-by: Randy Dunlap rdunlap@infradead.org Reviewed-by: "Huang, Ying" ying.huang@intel.com Reviewed-by: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Acked-by: Michal Hocko mhocko@suse.com Cc: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Feng Tang feng.tang@intel.com Cc: Michal Hocko mhocko@kernel.org Cc: Andrea Arcangeli aarcange@redhat.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Mike Kravetz mike.kravetz@oracle.com Cc: Randy Dunlap rdunlap@infradead.org Cc: Vlastimil Babka vbabka@suse.cz Cc: Andi Kleen ak@linux.intel.com Cc: Dan Williams dan.j.williams@intel.com Cc: Huang Ying ying.huang@intel.com Cc: linux-api@vger.kernel.org Cc: Andrew Morton akpm@linux-foundation.org Cc: linux-mm@kvack.org Cc: stable@vger.kernel.org # 5.17+ --- mm/mempolicy.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 61aa9aedb728..02c8a712282f 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1540,6 +1540,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le * the home node for vmas we already updated before. */ if (new->mode != MPOL_BIND && new->mode != MPOL_PREFERRED_MANY) { + mpol_put(new); err = -EOPNOTSUPP; break; }