| Message ID | 20240627130134.1006059-1-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [for-4.19] tools/dombuilder: Correct the length calculation in xc_dom_alloc_segment() | expand |
On Thu, Jun 27, 2024 at 02:01:34PM +0100, Andrew Cooper wrote: > xc_dom_alloc_segment() is passed a size in bytes, calculates a size in pages > from it, then fills in the new segment information with a bytes value > re-calculated from the number of pages. > > This causes the module information given to the guest (MB, or PVH) to have > incorrect sizes; specifically, sizes rounded up to the next page. > > This in turn is problematic for Xen. When Xen finds a gzipped module, it > peeks at the end metadata to judge the decompressed size, which is a -4 > backreference from the reported end of the module. > > Fill in seg->vend using the correct number of bytes. > > Fixes: ea7c8a3d0e82 ("libxc: reorganize domain builder guest memory allocator") > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> > --- > > For 4.19: This was discovered when trying to test Daniel's gzip cleanup for > Hyperlaunch. It's a subtle bug, hidden inside a second bug which isn't > appropriate content for 4.20. Acked-by: Anthony PERARD <anthony.perard@vates.tech> Thanks,
On Thu, 2024-06-27 at 14:01 +0100, Andrew Cooper wrote: > xc_dom_alloc_segment() is passed a size in bytes, calculates a size > in pages > from it, then fills in the new segment information with a bytes value > re-calculated from the number of pages. > > This causes the module information given to the guest (MB, or PVH) to > have > incorrect sizes; specifically, sizes rounded up to the next page. > > This in turn is problematic for Xen. When Xen finds a gzipped > module, it > peeks at the end metadata to judge the decompressed size, which is a > -4 > backreference from the reported end of the module. > > Fill in seg->vend using the correct number of bytes. > > Fixes: ea7c8a3d0e82 ("libxc: reorganize domain builder guest memory > allocator") > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> > --- > CC: Anthony PERARD <anthony@xenproject.org> > CC: Juergen Gross <jgross@suse.com> > CC: Oleksii Kurochko <oleksii.kurochko@gmail.com> > > For 4.19: This was discovered when trying to test Daniel's gzip > cleanup for > Hyperlaunch. It's a subtle bug, hidden inside a second bug which > isn't > appropriate content for 4.20. > --- Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com> ~ Oleksii > tools/libs/guest/xg_dom_core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/libs/guest/xg_dom_core.c > b/tools/libs/guest/xg_dom_core.c > index c4f4e7f3e27a..f5521d528be1 100644 > --- a/tools/libs/guest/xg_dom_core.c > +++ b/tools/libs/guest/xg_dom_core.c > @@ -601,7 +601,7 @@ int xc_dom_alloc_segment(struct xc_dom_image > *dom, > memset(ptr, 0, pages * page_size); > > seg->vstart = start; > - seg->vend = dom->virt_alloc_end; > + seg->vend = start + size; > > DOMPRINTF("%-20s: %-12s : 0x%" PRIx64 " -> 0x%" PRIx64 > " (pfn 0x%" PRIpfn " + 0x%" PRIpfn " pages)",
diff --git a/tools/libs/guest/xg_dom_core.c b/tools/libs/guest/xg_dom_core.c index c4f4e7f3e27a..f5521d528be1 100644 --- a/tools/libs/guest/xg_dom_core.c +++ b/tools/libs/guest/xg_dom_core.c @@ -601,7 +601,7 @@ int xc_dom_alloc_segment(struct xc_dom_image *dom, memset(ptr, 0, pages * page_size); seg->vstart = start; - seg->vend = dom->virt_alloc_end; + seg->vend = start + size; DOMPRINTF("%-20s: %-12s : 0x%" PRIx64 " -> 0x%" PRIx64 " (pfn 0x%" PRIpfn " + 0x%" PRIpfn " pages)",
xc_dom_alloc_segment() is passed a size in bytes, calculates a size in pages from it, then fills in the new segment information with a bytes value re-calculated from the number of pages. This causes the module information given to the guest (MB, or PVH) to have incorrect sizes; specifically, sizes rounded up to the next page. This in turn is problematic for Xen. When Xen finds a gzipped module, it peeks at the end metadata to judge the decompressed size, which is a -4 backreference from the reported end of the module. Fill in seg->vend using the correct number of bytes. Fixes: ea7c8a3d0e82 ("libxc: reorganize domain builder guest memory allocator") Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Anthony PERARD <anthony@xenproject.org> CC: Juergen Gross <jgross@suse.com> CC: Oleksii Kurochko <oleksii.kurochko@gmail.com> For 4.19: This was discovered when trying to test Daniel's gzip cleanup for Hyperlaunch. It's a subtle bug, hidden inside a second bug which isn't appropriate content for 4.20. --- tools/libs/guest/xg_dom_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)