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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v5 08/16] livepatch/arm/x86: Check payload for for unwelcomed symbols.
> > 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 f46990e..ec74beb 100644
> > --- a/xen/common/livepatch_elf.c
> > +++ b/xen/common/livepatch_elf.c
> > @@ -251,6 +251,13 @@ static int elf_get_sym(struct livepatch_elf *elf,
> > const void *data)
> >
> > sym[i].sym = s;
> > sym[i].name = strtab_sec->data + delta;
> > + /* e.g. On ARM we should NEVER see $t* symbols. */
>
> I'd prefer this comment in ARM's arch_livepatch_symbol_deny.
I removed the comment from common code. With the latest patch each architecture
has its own implementation of arch_livepatch_symbol_deny.
>
> Either way,
> Reviewed-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Thanks.
Here is how the updated patch looks like:
From b84b478c4214f97e809f659fe348493c48a51d0c Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Tue, 13 Sep 2016 13:15:07 -0400
Subject: [PATCH v6] 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>
---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
v3: New submission.
Use &sym[i] instead of sym (as that will always be NULL).
v4: Use bool instead of int for return
Update comment in common code about ARM odd symbols.
s/_check/_deny/ to make it more clear.
v5: Also check for $t.* wildcard.
Use Julien's variant where we roll the [2] check in the return.
v6: s/suppose/supposed/ in commit description.
Move arch_livepatch_symbol_deny in arm[32|64]/livepatch.c
Added Julien's Reviewed-by.
Added Ross's Reviewed-by.
Removed comment from common code talking about $t symbol.
---
xen/arch/arm/arm32/livepatch.c | 13 +++++++++++++
xen/arch/arm/arm64/livepatch.c | 7 +++++++
xen/arch/x86/livepatch.c | 7 +++++++
xen/common/livepatch_elf.c | 6 ++++++
xen/include/xen/livepatch.h | 2 ++
5 files changed, 35 insertions(+)
diff --git a/xen/arch/arm/arm32/livepatch.c b/xen/arch/arm/arm32/livepatch.c
index 80f9646..5fc2e63 100644
--- a/xen/arch/arm/arm32/livepatch.c
+++ b/xen/arch/arm/arm32/livepatch.c
@@ -20,6 +20,19 @@ int arch_livepatch_verify_elf(const struct livepatch_elf
*elf)
return -EOPNOTSUPP;
}
+bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf,
+ const struct livepatch_elf_sym *sym)
+{
+ /*
+ * Xen does not use Thumb instructions - and we should not see any of
+ * them. If we do, abort.
+ */
+ if ( sym->name && sym->name[0] == '$' && 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);
--
2.4.11
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