uprobes: Change write_opcode() to use FOLL_FORCE
write_opcode()->get_user_pages() needs FOLL_FORCE to ensure we can read the page even if the probed task did mprotect(PROT_NONE) after uprobe_register(). Without FOLL_WRITE, FOLL_FORCE doesn't have any side effect but allows to read the !VM_READ memory. Otherwiese the subsequent uprobe_unregister()->set_orig_insn() fails and we leak "int3". If that task does mprotect(PROT_READ | EXEC) and execute the probed insn later it will be killed. Note: in fact this is also needed for _register, see the next patch. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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@ -221,7 +221,7 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
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retry:
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/* Read the page with vaddr into memory */
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ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
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ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma);
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if (ret <= 0)
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return ret;
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