entry, kasan, x86: Disallow overriding mem*() functions

KASAN cannot just hijack the mem*() functions, it needs to emit
__asan_mem*() variants if it wants instrumentation (other sanitizers
already do this).

  vmlinux.o: warning: objtool: sync_regs+0x24: call to memcpy() leaves .noinstr.text section
  vmlinux.o: warning: objtool: vc_switch_off_ist+0xbe: call to memcpy() leaves .noinstr.text section
  vmlinux.o: warning: objtool: fixup_bad_iret+0x36: call to memset() leaves .noinstr.text section
  vmlinux.o: warning: objtool: __sev_get_ghcb+0xa0: call to memcpy() leaves .noinstr.text section
  vmlinux.o: warning: objtool: __sev_put_ghcb+0x35: call to memcpy() leaves .noinstr.text section

Remove the weak aliases to ensure nobody hijacks these functions and
add them to the noinstr section.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195542.028523143@infradead.org

diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index dd8cd8831251fc62f77f00ebaeee5028a58b9f00..a64017602010ea8a4b61538f25918c6e58da7887 100644 (file)
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -8,7 +8,7 @@
 #include <asm/alternative.h>
 #include <asm/export.h>
 
-.pushsection .noinstr.text, "ax"
+.section .noinstr.text, "ax"
 
 /*
  * We build a jump to memcpy_orig by default which gets NOPped out on
@@ -43,7 +43,7 @@ SYM_TYPED_FUNC_START(__memcpy)
 SYM_FUNC_END(__memcpy)
 EXPORT_SYMBOL(__memcpy)
 
-SYM_FUNC_ALIAS_WEAK(memcpy, __memcpy)
+SYM_FUNC_ALIAS(memcpy, __memcpy)
 EXPORT_SYMBOL(memcpy)
 
 /*
@@ -184,4 +184,3 @@ SYM_FUNC_START_LOCAL(memcpy_orig)
        RET
 SYM_FUNC_END(memcpy_orig)
 
-.popsection

diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
index 724bbf83eb5b0910819b83a8cb5b349d45a6fe8d..02661861e5dd9665966dbd3a830ed6a7d4054dba 100644 (file)
--- a/arch/x86/lib/memmove_64.S
+++ b/arch/x86/lib/memmove_64.S
@@ -13,6 +13,8 @@
 
 #undef memmove
 
+.section .noinstr.text, "ax"
+
 /*
  * Implement memmove(). This can handle overlap between src and dst.
  *
@@ -213,5 +215,5 @@ SYM_FUNC_START(__memmove)
 SYM_FUNC_END(__memmove)
 EXPORT_SYMBOL(__memmove)
 
-SYM_FUNC_ALIAS_WEAK(memmove, __memmove)
+SYM_FUNC_ALIAS(memmove, __memmove)
 EXPORT_SYMBOL(memmove)

diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index fc9ffd3ff3b213a38448d5fbff5493989e21a158..6143b1a6fa2caa0d5977d22c3f1c23456ff6d3bf 100644 (file)
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -6,6 +6,8 @@
 #include <asm/alternative.h>
 #include <asm/export.h>
 
+.section .noinstr.text, "ax"
+
 /*
  * ISO C memset - set a memory block to a byte value. This function uses fast
  * string to get better performance than the original function. The code is
@@ -43,7 +45,7 @@ SYM_FUNC_START(__memset)
 SYM_FUNC_END(__memset)
 EXPORT_SYMBOL(__memset)
 
-SYM_FUNC_ALIAS_WEAK(memset, __memset)
+SYM_FUNC_ALIAS(memset, __memset)
 EXPORT_SYMBOL(memset)
 
 /*

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index ea8cf1310b1e81ea6500bf8ddff248cb75e8c38c..71c15438afcfc004876a8e47fc1becfdabca6c08 100644 (file)
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -618,6 +618,10 @@ void __asan_set_shadow_f3(const void *addr, size_t size);
 void __asan_set_shadow_f5(const void *addr, size_t size);
 void __asan_set_shadow_f8(const void *addr, size_t size);
 
+void *__asan_memset(void *addr, int c, size_t len);
+void *__asan_memmove(void *dest, const void *src, size_t len);
+void *__asan_memcpy(void *dest, const void *src, size_t len);
+
 void __hwasan_load1_noabort(unsigned long addr);
 void __hwasan_store1_noabort(unsigned long addr);
 void __hwasan_load2_noabort(unsigned long addr);

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 2fba1f51f042eaf49ee7fd8b5f4af37211a27bb2..98269936a5e4b799f8d00c781ba4aca2cd171f27 100644 (file)
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -38,6 +38,12 @@ bool __kasan_check_write(const volatile void *p, unsigned int size)
 }
 EXPORT_SYMBOL(__kasan_check_write);
 
+#ifndef CONFIG_GENERIC_ENTRY
+/*
+ * CONFIG_GENERIC_ENTRY relies on compiler emitted mem*() calls to not be
+ * instrumented. KASAN enabled toolchains should emit __asan_mem*() functions
+ * for the sites they want to instrument.
+ */
 #undef memset
 void *memset(void *addr, int c, size_t len)
 {
@@ -68,6 +74,38 @@ void *memcpy(void *dest, const void *src, size_t len)
 
        return __memcpy(dest, src, len);
 }
+#endif
+
+void *__asan_memset(void *addr, int c, size_t len)
+{
+       if (!kasan_check_range((unsigned long)addr, len, true, _RET_IP_))
+               return NULL;
+
+       return __memset(addr, c, len);
+}
+EXPORT_SYMBOL(__asan_memset);
+
+#ifdef __HAVE_ARCH_MEMMOVE
+void *__asan_memmove(void *dest, const void *src, size_t len)
+{
+       if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||
+           !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))
+               return NULL;
+
+       return __memmove(dest, src, len);
+}
+EXPORT_SYMBOL(__asan_memmove);
+#endif
+
+void *__asan_memcpy(void *dest, const void *src, size_t len)
+{
+       if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||
+           !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))
+               return NULL;
+
+       return __memcpy(dest, src, len);
+}
+EXPORT_SYMBOL(__asan_memcpy);
 
 void kasan_poison(const void *addr, size_t size, u8 value, bool init)
 {

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 9767babfd9edaa686d5a1387c12dae7d88d624ad..92554c5c80aafec8f5df62be8d9ce5f7765ecab5 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1074,6 +1074,9 @@ static const char *uaccess_safe_builtin[] = {
        "__asan_store16_noabort",
        "__kasan_check_read",
        "__kasan_check_write",
+       "__asan_memset",
+       "__asan_memmove",
+       "__asan_memcpy",
        /* KASAN in-line */
        "__asan_report_load_n_noabort",
        "__asan_report_load1_noabort",