From: Roger Pau Monné <roger.pau@citrix.com>
Date: Fri, 8 Apr 2022 08:27:11 +0000 (+0200)
Subject: livepatch: avoid relocations referencing ignored section symbols
X-Git-Tag: archive/raspbian/4.17.0-1+rpi1^2~33^2~758
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=9120b5737f517fe9d2a3936c38d3a2211630323b;p=xen.git

livepatch: avoid relocations referencing ignored section symbols

Track whether symbols belong to ignored sections in order to avoid
applying relocations referencing those symbols. The address of such
symbols won't be resolved and thus the relocation will likely fail or
write garbage to the destination.

Return an error in that case, as leaving unresolved relocations would
lead to malfunctioning payload code.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Tested-by: Bjoern Doebel <doebel@amazon.de>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
---

diff --git a/xen/arch/arm/arm32/livepatch.c b/xen/arch/arm/arm32/livepatch.c
index 5a06467008..3c50283b2a 100644
--- a/xen/arch/arm/arm32/livepatch.c
+++ b/xen/arch/arm/arm32/livepatch.c
@@ -272,6 +272,13 @@ int arch_livepatch_perform(struct livepatch_elf *elf,
                    elf->name, symndx);
             return -EINVAL;
         }
+        else if ( elf->sym[symndx].ignored )
+        {
+            printk(XENLOG_ERR LIVEPATCH
+                   "%s: Relocation against ignored symbol %s cannot be resolved\n",
+                   elf->name, elf->sym[symndx].name);
+            return -EINVAL;
+        }
 
         val = elf->sym[symndx].sym->st_value; /* S */
 
diff --git a/xen/arch/arm/arm64/livepatch.c b/xen/arch/arm/arm64/livepatch.c
index 6ec8dc60f0..62d2ef373a 100644
--- a/xen/arch/arm/arm64/livepatch.c
+++ b/xen/arch/arm/arm64/livepatch.c
@@ -270,6 +270,13 @@ int arch_livepatch_perform_rela(struct livepatch_elf *elf,
                    elf->name, symndx);
             return -EINVAL;
         }
+        else if ( elf->sym[symndx].ignored )
+        {
+            printk(XENLOG_ERR LIVEPATCH
+                   "%s: Relocation against ignored symbol %s cannot be resolved\n",
+                   elf->name, elf->sym[symndx].name);
+            return -EINVAL;
+        }
 
         val = elf->sym[symndx].sym->st_value +  r->r_addend; /* S+A */
 
diff --git a/xen/arch/x86/livepatch.c b/xen/arch/x86/livepatch.c
index 78c35f1fef..f2d783fdc5 100644
--- a/xen/arch/x86/livepatch.c
+++ b/xen/arch/x86/livepatch.c
@@ -291,6 +291,13 @@ int arch_livepatch_perform_rela(struct livepatch_elf *elf,
                    elf->name, symndx);
             return -EINVAL;
         }
+        else if ( elf->sym[symndx].ignored )
+        {
+            printk(XENLOG_ERR LIVEPATCH
+                   "%s: Relocation against ignored symbol %s cannot be resolved\n",
+                   elf->name, elf->sym[symndx].name);
+            return -EINVAL;
+        }
 
         val = r->r_addend + elf->sym[symndx].sym->st_value;
 
diff --git a/xen/common/livepatch_elf.c b/xen/common/livepatch_elf.c
index b089cacb1c..45d73912a3 100644
--- a/xen/common/livepatch_elf.c
+++ b/xen/common/livepatch_elf.c
@@ -334,7 +334,13 @@ int livepatch_elf_resolve_symbols(struct livepatch_elf *elf)
             }
 
             if ( livepatch_elf_ignore_section(elf->sec[idx].sec) )
+            {
+                dprintk(XENLOG_DEBUG, LIVEPATCH
+                        "%s: Symbol %s from section %s ignored\n",
+                        elf->name, elf->sym[i].name, elf->sec[idx].name);
+                elf->sym[i].ignored = true;
                 break;
+            }
 
             st_value += (unsigned long)elf->sec[idx].load_addr;
             if ( elf->sym[i].name )
diff --git a/xen/include/xen/livepatch_elf.h b/xen/include/xen/livepatch_elf.h
index 5b1ec469da..7116deaddc 100644
--- a/xen/include/xen/livepatch_elf.h
+++ b/xen/include/xen/livepatch_elf.h
@@ -22,6 +22,7 @@ struct livepatch_elf_sec {
 struct livepatch_elf_sym {
     const Elf_Sym *sym;
     const char *name;
+    bool ignored;
 };
 
 struct livepatch_elf {