Re: [PATCH] powerpc/uprobes: Don't allow probe on suffix of prefixed instruction
From: Oleg Nesterov <oleg@redhat.com>
Date: 2021-01-19 18:29:22
Also in:
lkml
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?
quoted hunk ↗ jump to hunk
+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.