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X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTMwMDA4OSBTYWx0ZWRfX6u080+2JoTke w4R8eLsUpdb21B5WC9g8Zub7XQT9qF8OFevlJsmPe0nYjATOAQa7z51UXwvUm8ie92Y7rpjksV3 mPQwC/SYvhSFSwieeERNhCJs9Z50o4U2H/O49+qxnzfOft8QZ3EfSCSjhCyGjvzEZ8xLf6Wp5BV vml0XBzT0Q5/3ymzK8aR+aDHDsAR7j9hcZBt1ZICC0IFnTJoTx3ZUfR7cIDd1xGcAlu3ETEqLl6 sR3431/p9J77HnN2li9AWUTXJhRGKA9KgqarXKAurqnFVhswsO6JfB36G0RBQDOTt4YdluyXwVP +pDlX14i01nO8utNB8iW3H42/NGwihFvtdPMLzJcORd8ORHuJjOKqyMKHFsRNmUK1Jvy1jV0n54 D+RJz3WkeSZ+zofCD8BZBF2y02EeI/6YygkB3PIuZAz0ett0klzKm/weNXNp+McolrvE9WsC X-Proofpoint-GUID: cah4SK2yg8xjoEQn2tvOVK_Ppz8u2JJx X-Authority-Analysis: v=2.4 cv=UvhjN/wB c=1 sm=1 tr=0 ts=683986ba b=1 cx=c_pps a=zPCbziy225d3KhSqZt3L1A==:117 a=zPCbziy225d3KhSqZt3L1A==:17 a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=dt9VzEwgFbYA:10 a=GoEa3M9JfhUA:10 a=i0EeH86SAAAA:8 a=20KFwNOVAAAA:8 a=yPCof4ZbAAAA:8 a=pdG_qfMyCWuCLcrjtW4A:9 a=CjuIK1q_8ugA:10 cc=ntf awl=host:13206 X-Proofpoint-ORIG-GUID: cah4SK2yg8xjoEQn2tvOVK_Ppz8u2JJx On Thu, May 29, 2025 at 03:56:48PM +0000, Pu Lehui wrote: > From: Pu Lehui > > When executing move_ptes, the new_pte must be NULL, otherwise it will be > overwritten by the old_pte, and cause the abnormal new_pte to be leaked. > In order to make this problem to be more explicit, let's add > WARN_ON_ONCE when new_pte is not NULL. > > Suggested-by: Oleg Nesterov > Signed-off-by: Pu Lehui Reviewed-by: Lorenzo Stoakes (both this and the amended version :) > --- > mm/mremap.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/mremap.c b/mm/mremap.c > index 83e359754961..4e2491f8c2ce 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -237,6 +237,8 @@ static int move_ptes(struct pagetable_move_control *pmc, > > for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, > new_pte++, new_addr += PAGE_SIZE) { > + WARN_ON_ONCE(!pte_none(*new_pte)); > + I mean, we really really should not ever be seeing a mapped PTE here, so I think a WARN_ON_ONCE() is fine. We unmap anything ahead of time, and only I think this uprobe breakpoint installation would ever cause this to be the case. We can make this a VM_WARN_ON_ONCE() too I suppose, just in case there's something we're not thinking of, but I'd say at some point we'd want to change it to a WARN_ON_ONCE(). > if (pte_none(ptep_get(old_pte))) > continue; > > -- > 2.34.1 >