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gru: fix potential use-after-free when purging GRU tlbs
Fix potential SGI GRU bug that could cause a use-after-free. If one thread in a task is flushing the GRU and another thread destroys the GRU context, there is the potential to access a table after it has been freed. Copy the gms pointer to a local variable before unlocking the gts table. Note that no refcnt is needed for the gms - the reference is held indirectly by the task's mm_struct. Signed-off-by: Jack Steiner <steiner@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -702,6 +702,7 @@ int gru_user_flush_tlb(unsigned long arg)
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{
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struct gru_thread_state *gts;
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struct gru_flush_tlb_req req;
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struct gru_mm_struct *gms;
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STAT(user_flush_tlb);
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if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
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@ -714,8 +715,9 @@ int gru_user_flush_tlb(unsigned long arg)
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if (!gts)
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return -EINVAL;
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gru_flush_tlb_range(gts->ts_gms, req.vaddr, req.len);
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gms = gts->ts_gms;
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gru_unlock_gts(gts);
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gru_flush_tlb_range(gms, req.vaddr, req.len);
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return 0;
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}
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