[Xen-devel] [PATCH v5 2/4] livepatch: Add limit of 2MB to payload .bss sections.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

The initial patch: 11ff40fa7bb5fdcc69a58d0fec49c904ffca4793
"xen/xsplice: Hypervisor implementation of XEN_XSPLICE_op" caps the
size of the binary at 2MB. We follow that in capping the size
of the .BSSes to be at maximum 2MB.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

---
Cc: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>

v5: Initial submission. Came about from conversation about
    "livepatch: Clear .bss when payload is reverted"
   - Use only one sh_flags comparison instead of two.
   - And check for the _right_ combination (WA).
---
 xen/common/livepatch_elf.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/xen/common/livepatch_elf.c b/xen/common/livepatch_elf.c
index cda9b27..e2264ad 100644
--- a/xen/common/livepatch_elf.c
+++ b/xen/common/livepatch_elf.c
@@ -86,7 +86,15 @@ static int elf_resolve_sections(struct livepatch_elf *elf, 
const void *data)
                     delta < sizeof(Elf_Ehdr) ? "at ELF header" : "is past 
end");
             return -EINVAL;
         }
-
+        else if ( (sec[i].sec->sh_flags & (SHF_WRITE | SHF_ALLOC)) &&
+                  sec[i].sec->sh_type == SHT_NOBITS &&
+                  sec[i].sec->sh_size > MB(2) )
+        {
+            /* Arbitrary limit. */
+            dprintk(XENLOG_ERR, LIVEPATCH "%s: Section [%u] .bss is bigger 
than 2MB!\n",
+                    elf->name, i);
+            return -EINVAL;
+        }
         sec[i].data = data + delta;
         /* Name is populated in elf_resolve_section_names. */
         sec[i].name = NULL;
-- 
2.4.11


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