Re: [patch] ioremap sanity check to catch mapping requestsexceeding the BAR sizes

From: Ingo Molnar
Date: Fri Sep 26 2008 - 03:39:41 EST



* Suresh Siddha <suresh.b.siddha@xxxxxxxxx> wrote:

> [patch] ioremap sanity check to catch mapping requests exceeding the BAR sizes
>
> Go through the iomem resource tree to check if any of the ioremap() requests
> span more than any slot in the iomem resource tree and do a WARN_ON() if we hit
> this check.
>
> This will raise a red-flag, if some driver is mapping more than what
> is needed. And hopefully identify possible corruptions much earlier.
>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>

applied to tip/core/resources, thanks Suresh.

one question:

> + for (p = p->child; p ; p = r_next(NULL, p, &l)) {
> + /*
> + * We can probably skip the resources with out
> + * IORESOURCE_IO attribute?
> + */
> + if (p->start >= addr + size)
> + continue;
> + if (p->end < addr)
> + continue;
> + if (p->start <= addr && (p->end >= addr + size - 1))
> + continue;
> + printk(KERN_WARNING "resource map sanity check conflict "
> + " 0x%llx 0x%llx 0x%llx 0x%llx %s\n",
> + addr, addr + size - 1, p->start, p->end, p->name);
> + err = -1;
> + break;

i think all the checks you added are precise to the byte and you allow
all the sensible ioremaps: which nest fully inside a single resource -
and you reject all the other partial overlap or multiple overlap
scenarios.

One potential thing to check for would be whether addr+size overlaps a
4GB boundary? That would almost always be a bug, and it could also cause
problems with the checks above if resource_t is 32 bits. The ioremap
code should already prevent it though.

Ingo
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