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    SubjectRe: [PATCH 2/2] vsprintf: don't dereference pointers to the first or last page
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    On Tue, 2018-03-06 at 19:11 +0100, Adam Borowski wrote:
    > As old code to avoid so is inconsistent, let's unify it within a
    > single
    > macro.
    >
    >
    > +#define IS_BAD_PTR(x) ((unsigned long)(x) >= (unsigned long)-
    > PAGE_SIZE \
    > + || (unsigned long)(x) < PAGE_SIZE)

    Oh, no.

    First of all, why it's a macro?

    Next, what prevents us to do it in place using IS_ERR() instead? (Btw, I
    have a patch for that, not published yet)

    > #define BAD_PTR_STRING(x) (!(x) ? "(null)" : IS_ERR(x) ? "(err)" :
    > "(invalid)")
    >
    > /**
    > @@ -589,7 +591,7 @@ char *string(char *buf, char *end, const char *s,
    > struct printf_spec spec)
    > int len = 0;
    > size_t lim = spec.precision;
    >
    > - if ((unsigned long)s < PAGE_SIZE)
    > + if (IS_BAD_PTR(s))
    > s = BAD_PTR_STRING(s);

    I don't think it's a good idea to change current behaviour.

    > @@ -1583,7 +1585,7 @@ char *device_node_string(char *buf, char *end,
    > struct device_node *dn,
    > if (!IS_ENABLED(CONFIG_OF))
    > return string(buf, end, "(!OF)", spec);
    >
    > - if ((unsigned long)dn < PAGE_SIZE)
    > + if (IS_BAD_PTR(dn))
    > return string(buf, end, BAD_PTR_STRING(dn), spec);

    This makes no sense. Explained in comment against patch 1.

    >
    > /* simple case without anything any more format specifiers */
    > @@ -1851,7 +1853,7 @@ char *pointer(const char *fmt, char *buf, char
    > *end, void *ptr,
    > {
    > const int default_width = 2 * sizeof(void *);
    >
    > - if (!ptr && *fmt != 'K' && *fmt != 'x') {
    > + if (IS_BAD_PTR(ptr) && *fmt != 'K' && *fmt != 'x') {
    > /*
    > * Print (null)/etc with the same width as a pointer
    > so it
    > * makes tabular output look nice.
    >

    --
    Andy Shevchenko <andriy.shevchenko@linux.intel.com>
    Intel Finland Oy

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