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powerpc: Skip stack validation checking alternate stacks if they are not allocated

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Stack validation in early boot can just bail out of checking alternate
stacks if they are not validated yet. Checking against a NULL stack
could cause NULLish pointer values to be considered valid.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221216115930.2667772-5-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2022-12-16 21:59:30 +10:00 committed by Michael Ellerman
parent dc222fa773
commit 1ee4e35076
1 changed files with 11 additions and 0 deletions
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11
arch/powerpc/kernel/process.c
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@ -2117,6 +2117,9 @@ static inline int valid_irq_stack(unsigned long sp, struct task_struct *p,
unsigned long stack_page;
unsigned long cpu = task_cpu(p);
if (!hardirq_ctx[cpu] || !softirq_ctx[cpu])
return 0;
stack_page = (unsigned long)hardirq_ctx[cpu];
if (sp >= stack_page && sp <= stack_page + THREAD_SIZE - nbytes)
return 1;
@ -2138,6 +2141,14 @@ static inline int valid_emergency_stack(unsigned long sp, struct task_struct *p,
if (!paca_ptrs)
return 0;
if (!paca_ptrs[cpu]->emergency_sp)
return 0;
# ifdef CONFIG_PPC_BOOK3S_64
if (!paca_ptrs[cpu]->nmi_emergency_sp || !paca_ptrs[cpu]->mc_emergency_sp)
return 0;
#endif
stack_page = (unsigned long)paca_ptrs[cpu]->emergency_sp - THREAD_SIZE;
if (sp >= stack_page && sp <= stack_page + THREAD_SIZE - nbytes)
return 1;