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powerpc/book3s64/radix: Remove WARN_ON in destroy_context()
On failed task initialization due to memory allocation failures, we can call into destroy_context() with process_tb entry already populated. This patch forces the process_tb entry to zero in destroy_context(). With this patch, we lose the ability to track if we are destroying a context without flushing the process table entry. WARNING: CPU: 4 PID: 6368 at arch/powerpc/mm/mmu_context_book3s64.c:246 destroy_context+0x58/0x340 NIP [c0000000000875f8] destroy_context+0x58/0x340 LR [c00000000013da18] __mmdrop+0x78/0x270 Call Trace: [c000000f7db77c80] [c00000000013da18] __mmdrop+0x78/0x270 [c000000f7db77cf0] [c0000000004d6a34] __do_execve_file.isra.13+0xbd4/0x1000 [c000000f7db77e00] [c0000000004d7428] sys_execve+0x58/0x70 [c000000f7db77e30] [c00000000000b388] system_call+0x5c/0x70 Reported-by: Priya M.A <priyama2@in.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> [mpe: Reformat/tweak comment wording] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20190918140103.24395-1-aneesh.kumar@linux.ibm.com
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@ -256,8 +256,21 @@ void destroy_context(struct mm_struct *mm)
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#ifdef CONFIG_SPAPR_TCE_IOMMU
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WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list));
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#endif
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/*
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* For tasks which were successfully initialized we end up calling
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* arch_exit_mmap() which clears the process table entry. And
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* arch_exit_mmap() is called before the required fullmm TLB flush
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* which does a RIC=2 flush. Hence for an initialized task, we do clear
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* any cached process table entries.
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*
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* The condition below handles the error case during task init. We have
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* set the process table entry early and if we fail a task
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* initialization, we need to ensure the process table entry is zeroed.
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* We need not worry about process table entry caches because the task
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* never ran with the PID value.
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*/
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if (radix_enabled())
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WARN_ON(process_tb[mm->context.id].prtb0 != 0);
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process_tb[mm->context.id].prtb0 = 0;
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else
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subpage_prot_free(mm);
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destroy_contexts(&mm->context);
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