[Xen-changelog] [xen master] livepatch/arm/x86: Check payload for for unwelcomed symbols.

[patchbot@xxxxxxx]

commit e04977e0c0c1aa50d7d1ca1f172af587776040a3
Author:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
AuthorDate: Tue Sep 13 13:15:07 2016 -0400
Commit:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CommitDate: Tue Sep 27 22:06:49 2016 -0400

    livepatch/arm/x86: Check payload for for unwelcomed symbols.
    
    Certain platforms, such as ARM [32|64] add extra mapping symbols
    such as $x (for ARM64 instructions), or more interesting to
    this patch: $t (for Thumb instructions). These symbols are supposed
    to help the final linker to make any adjustments (such as
    add an veneer). But more importantly - we do not compile Xen
    with any Thumb instructions (which are variable length) - and
    if we find these mapping symbols we should disallow such payload.
    
    Reviewed-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
    Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 xen/arch/arm/arm32/livepatch.c | 13 +++++++++++++
 xen/arch/arm/arm64/livepatch.c |  7 +++++++
 xen/arch/x86/livepatch.c       |  7 +++++++
 xen/common/livepatch_elf.c     |  6 ++++++
 xen/include/xen/livepatch.h    |  2 ++
 5 files changed, 35 insertions(+)

diff --git a/xen/arch/arm/arm32/livepatch.c b/xen/arch/arm/arm32/livepatch.c
index 80f9646..5fc2e63 100644
--- a/xen/arch/arm/arm32/livepatch.c
+++ b/xen/arch/arm/arm32/livepatch.c
@@ -20,6 +20,19 @@ int arch_livepatch_verify_elf(const struct livepatch_elf 
*elf)
     return -EOPNOTSUPP;
 }
 
+bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf,
+                                const struct livepatch_elf_sym *sym)
+{
+    /*
+     * Xen does not use Thumb instructions - and we should not see any of
+     * them. If we do, abort.
+     */
+    if ( sym->name && sym->name[0] == '$' && sym->name[1] == 't' )
+        return ( !sym->name[2] || sym->name[2] == '.' );
+
+    return false;
+}
+
 int arch_livepatch_perform_rela(struct livepatch_elf *elf,
                                 const struct livepatch_elf_sec *base,
                                 const struct livepatch_elf_sec *rela)
diff --git a/xen/arch/arm/arm64/livepatch.c b/xen/arch/arm/arm64/livepatch.c
index 774f845..f148927 100644
--- a/xen/arch/arm/arm64/livepatch.c
+++ b/xen/arch/arm/arm64/livepatch.c
@@ -90,6 +90,13 @@ int arch_livepatch_verify_elf(const struct livepatch_elf 
*elf)
     return 0;
 }
 
+bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf,
+                                const struct livepatch_elf_sym *sym)
+{
+    /* No special checks on ARM 64. */
+    return false;
+}
+
 enum aarch64_reloc_op {
     RELOC_OP_NONE,
     RELOC_OP_ABS,
diff --git a/xen/arch/x86/livepatch.c b/xen/arch/x86/livepatch.c
index 7a369a0..9663ef6 100644
--- a/xen/arch/x86/livepatch.c
+++ b/xen/arch/x86/livepatch.c
@@ -131,6 +131,13 @@ bool arch_livepatch_symbol_ok(const struct livepatch_elf 
*elf,
     return true;
 }
 
+bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf,
+                                const struct livepatch_elf_sym *sym)
+{
+    /* No special checks on x86. */
+    return false;
+}
+
 int arch_livepatch_perform_rel(struct livepatch_elf *elf,
                                const struct livepatch_elf_sec *base,
                                const struct livepatch_elf_sec *rela)
diff --git a/xen/common/livepatch_elf.c b/xen/common/livepatch_elf.c
index dec904a..c4a9633 100644
--- a/xen/common/livepatch_elf.c
+++ b/xen/common/livepatch_elf.c
@@ -251,6 +251,12 @@ static int elf_get_sym(struct livepatch_elf *elf, const 
void *data)
 
         sym[i].sym = s;
         sym[i].name = strtab_sec->data + delta;
+        if ( arch_livepatch_symbol_deny(elf, &sym[i]) )
+        {
+            dprintk(XENLOG_ERR, LIVEPATCH "%s: Symbol '%s' should not be in 
payload!\n",
+                    elf->name, sym[i].name);
+            return -EINVAL;
+        }
     }
     elf->nsym = nsym;
 
diff --git a/xen/include/xen/livepatch.h b/xen/include/xen/livepatch.h
index e8c67d6..98ec012 100644
--- a/xen/include/xen/livepatch.h
+++ b/xen/include/xen/livepatch.h
@@ -50,6 +50,8 @@ bool_t is_patch(const void *addr);
 int arch_livepatch_verify_elf(const struct livepatch_elf *elf);
 bool arch_livepatch_symbol_ok(const struct livepatch_elf *elf,
                               const struct livepatch_elf_sym *sym);
+bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf,
+                                const struct livepatch_elf_sym *sym);
 int arch_livepatch_perform_rel(struct livepatch_elf *elf,
                                const struct livepatch_elf_sec *base,
                                const struct livepatch_elf_sec *rela);
--
generated by git-patchbot for /home/xen/git/xen.git#master

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