On failed task initialization due to memory allocation failures,
we can call into destroy_context with process_tb entry set. 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 <priya...@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
arch/powerpc/mm/book3s64/mmu_context.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/book3s64/mmu_context.c
b/arch/powerpc/mm/book3s64/mmu_context.c
index 2d0cb5ba9a47..3a0f5ab190ec 100644
--- a/arch/powerpc/mm/book3s64/mmu_context.c
+++ b/arch/powerpc/mm/book3s64/mmu_context.c
@@ -256,8 +256,18 @@ void destroy_context(struct mm_struct *mm)
#ifdef CONFIG_SPAPR_TCE_IOMMU
WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list));
#endif
+ /* For tasks which were successfully initialized we would end up
+ * calling arch_exit_mmap which clears the process table entry.
+ * arch_exit_mmap get called before the required fullmm tlb flush
+ * which does a RIC=2 flush. Hence for an initialized task, we do
+ * clear any cached process table entry. The condition below handles
+ * the error case during task init. We do set the process table entry
+ * early and if we fail a task initialization, we need to ensure
+ * the process table entry is zeroed. We need not worry about process
+ * table entry caches because the task never ran with the PID value.
+ */
if (radix_enabled())
- WARN_ON(process_tb[mm->context.id].prtb0 != 0);
+ process_tb[mm->context.id].prtb0 = 0;
else
subpage_prot_free(mm);
destroy_contexts(&mm->context);
--
2.21.0
