Messages in this thread | | | Date | Tue, 19 Jan 2021 18:26:03 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] powerpc/uprobes: Don't allow probe on suffix of prefixed instruction |
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On 01/19, Ravi Bangoria wrote: > > Probe on 2nd word of a prefixed instruction is invalid scenario and > should be restricted.
I don't understand this ppc-specific problem, but...
> +#ifdef CONFIG_PPC64 > +int arch_uprobe_verify_opcode(struct page *page, unsigned long vaddr, > + uprobe_opcode_t opcode) > +{ > + uprobe_opcode_t prefix; > + void *kaddr; > + struct ppc_inst inst; > + > + /* Don't check if vaddr is pointing to the beginning of page */ > + if (!(vaddr & ~PAGE_MASK)) > + return 0;
So the fix is incomplete? Or insn at the start of page can't be prefixed?
> +int __weak arch_uprobe_verify_opcode(struct page *page, unsigned long vaddr, > + uprobe_opcode_t opcode) > +{ > + return 0; > +} > + > static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode) > { > uprobe_opcode_t old_opcode; > @@ -275,6 +281,8 @@ static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t > if (is_swbp_insn(new_opcode)) { > if (is_swbp) /* register: already installed? */ > return 0; > + if (arch_uprobe_verify_opcode(page, vaddr, old_opcode)) > + return -EINVAL;
Well, this doesn't look good...
To me it would be better to change the prepare_uprobe() path to copy the potential prefix into uprobe->arch and check ppc_inst_prefixed() in arch_uprobe_analyze_insn(). What do you think?
Oleg.
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