4.4-stable review patch. If anyone has any objections, please let me know.
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From: Yisheng Xie xieyisheng1@huawei.com
[ Upstream commit 8970a63e965b43288c4f5f40efbc2bbf80de7f16 ]
Alexander reported a use of uninitialized memory in __mpol_equal(), which is caused by incorrect use of preferred_node.
When mempolicy in mode MPOL_PREFERRED with flags MPOL_F_LOCAL, it uses numa_node_id() instead of preferred_node, however, __mpol_equal() uses preferred_node without checking whether it is MPOL_F_LOCAL or not.
[akpm@linux-foundation.org: slight comment tweak] Link: http://lkml.kernel.org/r/4ebee1c2-57f6-bcb8-0e2d-1833d1ee0bb7@huawei.com Fixes: fc36b8d3d819 ("mempolicy: use MPOL_F_LOCAL to Indicate Preferred Local Policy") Signed-off-by: Yisheng Xie xieyisheng1@huawei.com Reported-by: Alexander Potapenko glider@google.com Tested-by: Alexander Potapenko glider@google.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: Dmitriy Vyukov dvyukov@google.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Michal Hocko mhocko@kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/mempolicy.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2142,6 +2142,9 @@ bool __mpol_equal(struct mempolicy *a, s case MPOL_INTERLEAVE: return !!nodes_equal(a->v.nodes, b->v.nodes); case MPOL_PREFERRED: + /* a's ->flags is the same as b's */ + if (a->flags & MPOL_F_LOCAL) + return true; return a->v.preferred_node == b->v.preferred_node; default: BUG();