[xen staging-4.16] livepatch: avoid relocations referencing ignored section symbols

[patchbot@xxxxxxx]

commit b953760d0b564478e232e7e64823d2a1506e92b5
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Fri Apr 8 14:59:27 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Apr 8 14:59:27 2022 +0200

    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@xxxxxxxxxx>
    Tested-by: Bjoern Doebel <doebel@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
    master commit: 9120b5737f517fe9d2a3936c38d3a2211630323b
    master date: 2022-04-08 10:27:11 +0200
---
 xen/arch/arm/arm32/livepatch.c  | 7 +++++++
 xen/arch/arm/arm64/livepatch.c  | 7 +++++++
 xen/arch/x86/livepatch.c        | 7 +++++++
 xen/common/livepatch_elf.c      | 6 ++++++
 xen/include/xen/livepatch_elf.h | 1 +
 5 files changed, 28 insertions(+)

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 a3cb63a7ea..0172610ebf 100644
--- a/xen/arch/x86/livepatch.c
+++ b/xen/arch/x86/livepatch.c
@@ -290,6 +290,13 @@ 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 {
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.16