Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH] lib/string_helpers.c: fix infinite loop in string_get_size() | Date | Mon, 14 Sep 2015 11:16:55 +0200 |
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James Bottomley <jbottomley@odin.com> writes:
> On Thu, 2015-09-10 at 16:08 -0700, Andrew Morton wrote: >> On Fri, 4 Sep 2015 14:56:33 +0200 Vitaly Kuznetsov <vkuznets@redhat.com> wrote: >> >> > string_get_size(1, 512, 0, ..., ...) call results in an infinite loop. The >> > problem is that if size == 0 when we start calculating sf_cap this loop >> > will never end. >> > >> > The caller causing the issue is sd_read_capacity(), the problem was noticed >> > on Hyper-V. >> >> When fixing bugs, please provide enough info for others to be able to >> understand which kernel version(s) need the fix. In this case: what >> end-user action triggers this bug? (iow, how does sdkp->capacity >> become zero?) > > Any more details. The attached programme, which is cut straight out of > the algorithm in string_helpers.c and modified for a C environment > slightly (only in do_div and the typedefs) produces this > > hello > STRING IS 512 B > > With your input, so I don't think the problem is where you think it > is.
Sorry for delayed reply, I was traveling.
Please change string_get_size(1, 512, STRING_UNITS_2, buf, sizeof(buf));
to string_get_size(1, 512, STRING_UNITS_10, buf, sizeof(buf));
in your test.c program to see the issue, it will enter the infinite loop as well.
Regardless to Hyper-V I think such library function shouldn't do such nasty things (but I'll try to investigate why such small size was reported).
-- Vitaly
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