[Xen-changelog] [xen stable-4.10] x86/setup: Avoid OoB E820 lookup when calculating the L1TF safe address

[patchbot@xxxxxxx]

commit 24bc2e31b236afd23d108ec173526210dadd78d5
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Sep 14 13:21:56 2018 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Sep 14 13:21:56 2018 +0200

    x86/setup: Avoid OoB E820 lookup when calculating the L1TF safe address
    
    A number of corner cases (most obviously, no-real-mode and no Multiboot 
memory
    map) can end up with e820_raw.nr_map being 0, at which point the L1TF
    calculation will underflow.
    
    Spotted by Coverity.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    master commit: 3e4ec07e14bce81f6ae22c31ff1302d1f297a226
    master date: 2018-08-16 18:10:07 +0100
---
 xen/arch/x86/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 1e9eecae04..91520e7612 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -910,7 +910,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     /* Sanitise the raw E820 map to produce a final clean version. */
     max_page = raw_max_page = init_e820(memmap_type, &e820_raw);
 
-    if ( !efi_enabled(EFI_BOOT) )
+    if ( !efi_enabled(EFI_BOOT) && e820_raw.nr_map >= 1 )
     {
         /*
          * Supplement the heuristics in l1tf_calculations() by assuming that
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.10

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