Messages in this thread | | | Date | Mon, 20 Aug 2018 16:27:34 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH] x86/speculation/l1tf: fix overflow on l1tf_pfn_limit() on 32bit |
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On Mon 20-08-18 13:41:03, Vlastimil Babka wrote: > On 08/20/2018 12:49 PM, Michal Hocko wrote: > > On Mon 20-08-18 11:58:35, Vlastimil Babka wrote: > >> On 32bit PAE kernels on 64bit hardware with enough physical bits, > >> l1tf_pfn_limit() will overflow unsigned long. This in turn affects > >> max_swapfile_size() and can lead to swapon returning -EINVAL. This has been > >> observed in a 32bit guest with 42 bits physical address size, where > >> max_swapfile_size() overflows exactly to 1 << 32, thus zero, and produces the > >> following warning to dmesg: > >> > >> [ 6.396845] Truncating oversized swap area, only using 0k out of 2047996k > >> > >> Fix this by using unsigned long long instead. > >> > >> Reported-by: Dominique Leuenberger <dimstar@suse.de> > >> Reported-by: Adrian Schroeter <adrian@suse.de> > >> Fixes: 17dbca119312 ("x86/speculation/l1tf: Add sysfs reporting for l1tf") > >> Fixes: 377eeaa8e11f ("x86/speculation/l1tf: Limit swap file size to MAX_PA/2") > >> Cc: stable@vger.kernel.org > >> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> > > > > Looks good to me. I would probably use phys_addr_t which would be more > > descriptive but this is just minor thing. > > Hmm phys_addr_t is still 32bit on !PAE so there the overflow could still > happen. I guess max_swapfile_size() should skip the whole L1TF part for > !PAE since there is no pte inverting done anyway.
Yeah, I misremembered that we are already doing that.
> Also the value is "number of pages" which is not the same as "physical > address" so the phys_addr_t could be misleading anyway?
right
-- Michal Hocko SUSE Labs
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