[Xen-devel] Error ignored in xc_map_foreign_pages

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

It appears that xc_map_foreign_pages() handles return incorrectly :

    res = xc_map_foreign_bulk(xch, dom, prot, arr, err, num);
    if (res) {
        for (i = 0; i < num; i++) {
            if (err[i]) {
                errno = -err[i];
                munmap(res, num * PAGE_SIZE);
                res = NULL;
                break;
            }
        }
    }

The add to_physmap batch'd interface  actually will store errors
in the err array, and return 0 unless EFAULT or something like that.
See xenmem_add_to_physmap_batch(). The case I'm looking at, xentrace
calls here to map page which fails, but the return is 0 as the error is
succesfully copied by xen. But the error is missed above since res is 0.
xentrace does something again, and that causes xen crash. 

It appears the fix could be just removing the check for res above...

    res = xc_map_foreign_bulk(xch, dom, prot, arr, err, num);
    for (i = 0; i < num; i++) {
        if (err[i]) {
         .....

What do you guys think?

thanks,
Mukesh

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