[Linux-kselftest-mirror] [PATCH 0/5] selftests/x86: fixes for !CONFIG_IA32_EMULATION and vsyscall=none

[Linux-kselftest-mirror] [PATCH 0/5] selftests/x86: fixes for !CONFIG_IA32_EMULATION and vsyscall=none

[linux]

On systems with CONFIG_IA32_EMULATION disabled and vsyscall disabled, a
couple of selftests fail spectacularly.

Also throw in a fix for the Makefile, which still wants to build the moved
5lvl test.

Dominik Brodowski (5):
  selftests/x86: 5lvl test has been moved
  selftests/x86: fix vDSO selftest segfault for vsyscall=none
  selftests/x86: do not rely on int $0x80 in test_mremap_vdso.c
  selftests/x86: do not rely on int $0x80 in single_step_syscall.c
  selftests/x86: disable tests requiring 32bit support on pure 64bit
    systems

 tools/testing/selftests/x86/Makefile              | 24 +++++++----
 tools/testing/selftests/x86/single_step_syscall.c |  5 ++-
 tools/testing/selftests/x86/test_mremap_vdso.c    |  4 ++
 tools/testing/selftests/x86/test_vdso.c           | 50 +++++++++++++++++++----
 4 files changed, 67 insertions(+), 16 deletions(-)

-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 0/5] selftests/x86: fixes for !CONFIG_IA32_EMULATION and vsyscall=none

[Dominik Brodowski]

On systems with CONFIG_IA32_EMULATION disabled and vsyscall disabled, a
couple of selftests fail spectacularly.

Also throw in a fix for the Makefile, which still wants to build the moved
5lvl test.

Dominik Brodowski (5):
  selftests/x86: 5lvl test has been moved
  selftests/x86: fix vDSO selftest segfault for vsyscall=none
  selftests/x86: do not rely on int $0x80 in test_mremap_vdso.c
  selftests/x86: do not rely on int $0x80 in single_step_syscall.c
  selftests/x86: disable tests requiring 32bit support on pure 64bit
    systems

 tools/testing/selftests/x86/Makefile              | 24 +++++++----
 tools/testing/selftests/x86/single_step_syscall.c |  5 ++-
 tools/testing/selftests/x86/test_mremap_vdso.c    |  4 ++
 tools/testing/selftests/x86/test_vdso.c           | 50 +++++++++++++++++++----
 4 files changed, 67 insertions(+), 16 deletions(-)

-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 1/5] selftests/x86: 5lvl test has been moved

[linux]

Fixes: 235266b8e11c "selftests/vm: move 128TB mmap boundary test to generic directory"
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 10ca46df1449..ce2615a2d105 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -11,7 +11,7 @@ TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_sysc
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			vdso_restorer
-TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip 5lvl
+TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip
 
 TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
 TARGETS_C_64BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_64BIT_ONLY)
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 1/5] selftests/x86: 5lvl test has been moved

[Dominik Brodowski]

Fixes: 235266b8e11c "selftests/vm: move 128TB mmap boundary test to generic directory"
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 10ca46df1449..ce2615a2d105 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -11,7 +11,7 @@ TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_sysc
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			vdso_restorer
-TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip 5lvl
+TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip
 
 TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
 TARGETS_C_64BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_64BIT_ONLY)
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[linux]

The vDSO selftest tries to execute a vsyscall unconditionally, even if it
is not present on the test system (e.g. if booted with vsyscall=none or
with CONFIG_LEGACY_VSYSCALL_NONE=y set. Fix this by copying (and tweaking)
the vsyscall check from test_vsyscall.c

CC: Andrew Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/test_vdso.c | 50 ++++++++++++++++++++++++++++-----
 1 file changed, 43 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/x86/test_vdso.c b/tools/testing/selftests/x86/test_vdso.c
index 29973cde06d3..558c8207e7b9 100644
--- a/tools/testing/selftests/x86/test_vdso.c
+++ b/tools/testing/selftests/x86/test_vdso.c
@@ -28,18 +28,52 @@
 
 int nerrs = 0;
 
+typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
+
+getcpu_t vgetcpu;
+getcpu_t vdso_getcpu;
+
+static void *vsyscall_getcpu(void)
+{
 #ifdef __x86_64__
-# define VSYS(x) (x)
+	FILE *maps;
+	char line[128];
+	bool found = false;
+
+	maps = fopen("/proc/self/maps", "r");
+	if (!maps) /* might still be present, but ignore it here, as we test vDSO not vsyscall */
+		return NULL;
+
+	while (fgets(line, sizeof(line), maps)) {
+		char r, x;
+		void *start, *end;
+		char name[128];
+		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
+			   &start, &end, &r, &x, name) != 5)
+			continue;
+
+		if (strcmp(name, "[vsyscall]"))
+			continue;
+
+		/* assume entries are OK, as we test vDSO here not vsyscall */
+		found = true;
+		break;
+	}
+
+	fclose(maps);
+
+	if (!found) {
+		printf("Warning: failed to find vsyscall getcpu\n");
+		return NULL;
+	}
+	return (void *) (0xffffffffff600800);
 #else
-# define VSYS(x) 0
+	return NULL;
 #endif
+}
 
-typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
-
-const getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
-getcpu_t vdso_getcpu;
 
-void fill_function_pointers()
+static void fill_function_pointers()
 {
 	void *vdso = dlopen("linux-vdso.so.1",
 			    RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
@@ -54,6 +88,8 @@ void fill_function_pointers()
 	vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu");
 	if (!vdso_getcpu)
 		printf("Warning: failed to find getcpu in vDSO\n");
+
+	vgetcpu = (getcpu_t) vsyscall_getcpu();
 }
 
 static long sys_getcpu(unsigned * cpu, unsigned * node,
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[Dominik Brodowski]

The vDSO selftest tries to execute a vsyscall unconditionally, even if it
is not present on the test system (e.g. if booted with vsyscall=none or
with CONFIG_LEGACY_VSYSCALL_NONE=y set. Fix this by copying (and tweaking)
the vsyscall check from test_vsyscall.c

CC: Andrew Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/test_vdso.c | 50 ++++++++++++++++++++++++++++-----
 1 file changed, 43 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/x86/test_vdso.c b/tools/testing/selftests/x86/test_vdso.c
index 29973cde06d3..558c8207e7b9 100644
--- a/tools/testing/selftests/x86/test_vdso.c
+++ b/tools/testing/selftests/x86/test_vdso.c
@@ -28,18 +28,52 @@
 
 int nerrs = 0;
 
+typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
+
+getcpu_t vgetcpu;
+getcpu_t vdso_getcpu;
+
+static void *vsyscall_getcpu(void)
+{
 #ifdef __x86_64__
-# define VSYS(x) (x)
+	FILE *maps;
+	char line[128];
+	bool found = false;
+
+	maps = fopen("/proc/self/maps", "r");
+	if (!maps) /* might still be present, but ignore it here, as we test vDSO not vsyscall */
+		return NULL;
+
+	while (fgets(line, sizeof(line), maps)) {
+		char r, x;
+		void *start, *end;
+		char name[128];
+		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
+			   &start, &end, &r, &x, name) != 5)
+			continue;
+
+		if (strcmp(name, "[vsyscall]"))
+			continue;
+
+		/* assume entries are OK, as we test vDSO here not vsyscall */
+		found = true;
+		break;
+	}
+
+	fclose(maps);
+
+	if (!found) {
+		printf("Warning: failed to find vsyscall getcpu\n");
+		return NULL;
+	}
+	return (void *) (0xffffffffff600800);
 #else
-# define VSYS(x) 0
+	return NULL;
 #endif
+}
 
-typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
-
-const getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
-getcpu_t vdso_getcpu;
 
-void fill_function_pointers()
+static void fill_function_pointers()
 {
 	void *vdso = dlopen("linux-vdso.so.1",
 			    RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
@@ -54,6 +88,8 @@ void fill_function_pointers()
 	vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu");
 	if (!vdso_getcpu)
 		printf("Warning: failed to find getcpu in vDSO\n");
+
+	vgetcpu = (getcpu_t) vsyscall_getcpu();
 }
 
 static long sys_getcpu(unsigned * cpu, unsigned * node,
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 3/5] selftests/x86: do not rely on int $0x80 in test_mremap_vdso.c

[linux]

On 64bit builds, we should not rely on int $0x80 working (it only does if
CONFIG_IA32_EMULATION is enabled). Without this patch, the move test may
succeed, but the int $0x80 cause a segfault, resulting in a false negative
output of this selftest.

CC: Dmitry Safonov <dsafonov at virtuozzo.com>
CC: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/test_mremap_vdso.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
index bf0d687c7db7..64f11c8d9b76 100644
--- a/tools/testing/selftests/x86/test_mremap_vdso.c
+++ b/tools/testing/selftests/x86/test_mremap_vdso.c
@@ -90,8 +90,12 @@ int main(int argc, char **argv, char **envp)
 			vdso_size += PAGE_SIZE;
 		}
 
+#ifdef __i386__
 		/* Glibc is likely to explode now - exit with raw syscall */
 		asm volatile ("int $0x80" : : "a" (__NR_exit), "b" (!!ret));
+#else /* __x86_64__ */
+		syscall(SYS_exit, ret);
+#endif
 	} else {
 		int status;
 
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 3/5] selftests/x86: do not rely on int $0x80 in test_mremap_vdso.c

[Dominik Brodowski]

On 64bit builds, we should not rely on int $0x80 working (it only does if
CONFIG_IA32_EMULATION is enabled). Without this patch, the move test may
succeed, but the int $0x80 cause a segfault, resulting in a false negative
output of this selftest.

CC: Dmitry Safonov <dsafonov at virtuozzo.com>
CC: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/test_mremap_vdso.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
index bf0d687c7db7..64f11c8d9b76 100644
--- a/tools/testing/selftests/x86/test_mremap_vdso.c
+++ b/tools/testing/selftests/x86/test_mremap_vdso.c
@@ -90,8 +90,12 @@ int main(int argc, char **argv, char **envp)
 			vdso_size += PAGE_SIZE;
 		}
 
+#ifdef __i386__
 		/* Glibc is likely to explode now - exit with raw syscall */
 		asm volatile ("int $0x80" : : "a" (__NR_exit), "b" (!!ret));
+#else /* __x86_64__ */
+		syscall(SYS_exit, ret);
+#endif
 	} else {
 		int status;
 
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 4/5] selftests/x86: do not rely on int $0x80 in single_step_syscall.c

[linux]

On 64bit builds, we should not rely on int $0x80 working (it only does if
CONFIG_IA32_EMULATION is enabled). To keep the "Set TF and check int80"
test running on 64bit installs with CONFIG_IA32_EMULATION enabled, build
this test only if we can also build 32bit binaries (which should be a
good approximation for that).

CC: Dmitry Safonov <dsafonov at virtuozzo.com>
CC: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/Makefile              | 2 ++
 tools/testing/selftests/x86/single_step_syscall.c | 5 ++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index ce2615a2d105..371ae715c506 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -40,12 +40,14 @@ endef
 ifeq ($(CAN_BUILD_I386),1)
 all: all_32
 TEST_PROGS += $(BINARIES_32)
+EXTRA_CFLAGS += -DCAN_BUILD_32
 $(foreach t,$(TARGETS_C_32BIT_ALL),$(eval $(call gen-target-rule-32,$(t))))
 endif
 
 ifeq ($(CAN_BUILD_X86_64),1)
 all: all_64
 TEST_PROGS += $(BINARIES_64)
+EXTRA_CFLAGS += -DCAN_BUILD_64
 $(foreach t,$(TARGETS_C_64BIT_ALL),$(eval $(call gen-target-rule-64,$(t))))
 endif
 
diff --git a/tools/testing/selftests/x86/single_step_syscall.c b/tools/testing/selftests/x86/single_step_syscall.c
index a48da95c18fd..ddfdd635de16 100644
--- a/tools/testing/selftests/x86/single_step_syscall.c
+++ b/tools/testing/selftests/x86/single_step_syscall.c
@@ -119,7 +119,9 @@ static void check_result(void)
 
 int main()
 {
+#ifdef CAN_BUILD_32
 	int tmp;
+#endif
 
 	sethandler(SIGTRAP, sigtrap, 0);
 
@@ -139,12 +141,13 @@ int main()
 		      : : "c" (post_nop) : "r11");
 	check_result();
 #endif
-
+#ifdef CAN_BUILD_32
 	printf("[RUN]\tSet TF and check int80\n");
 	set_eflags(get_eflags() | X86_EFLAGS_TF);
 	asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid)
 			: INT80_CLOBBERS);
 	check_result();
+#endif
 
 	/*
 	 * This test is particularly interesting if fast syscalls use
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 4/5] selftests/x86: do not rely on int $0x80 in single_step_syscall.c

[Dominik Brodowski]

On 64bit builds, we should not rely on int $0x80 working (it only does if
CONFIG_IA32_EMULATION is enabled). To keep the "Set TF and check int80"
test running on 64bit installs with CONFIG_IA32_EMULATION enabled, build
this test only if we can also build 32bit binaries (which should be a
good approximation for that).

CC: Dmitry Safonov <dsafonov at virtuozzo.com>
CC: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/Makefile              | 2 ++
 tools/testing/selftests/x86/single_step_syscall.c | 5 ++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index ce2615a2d105..371ae715c506 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -40,12 +40,14 @@ endef
 ifeq ($(CAN_BUILD_I386),1)
 all: all_32
 TEST_PROGS += $(BINARIES_32)
+EXTRA_CFLAGS += -DCAN_BUILD_32
 $(foreach t,$(TARGETS_C_32BIT_ALL),$(eval $(call gen-target-rule-32,$(t))))
 endif
 
 ifeq ($(CAN_BUILD_X86_64),1)
 all: all_64
 TEST_PROGS += $(BINARIES_64)
+EXTRA_CFLAGS += -DCAN_BUILD_64
 $(foreach t,$(TARGETS_C_64BIT_ALL),$(eval $(call gen-target-rule-64,$(t))))
 endif
 
diff --git a/tools/testing/selftests/x86/single_step_syscall.c b/tools/testing/selftests/x86/single_step_syscall.c
index a48da95c18fd..ddfdd635de16 100644
--- a/tools/testing/selftests/x86/single_step_syscall.c
+++ b/tools/testing/selftests/x86/single_step_syscall.c
@@ -119,7 +119,9 @@ static void check_result(void)
 
 int main()
 {
+#ifdef CAN_BUILD_32
 	int tmp;
+#endif
 
 	sethandler(SIGTRAP, sigtrap, 0);
 
@@ -139,12 +141,13 @@ int main()
 		      : : "c" (post_nop) : "r11");
 	check_result();
 #endif
-
+#ifdef CAN_BUILD_32
 	printf("[RUN]\tSet TF and check int80\n");
 	set_eflags(get_eflags() | X86_EFLAGS_TF);
 	asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid)
 			: INT80_CLOBBERS);
 	check_result();
+#endif
 
 	/*
 	 * This test is particularly interesting if fast syscalls use
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 5/5] selftests/x86: disable tests requiring 32bit support on pure 64bit systems

[linux]

The ldt_gdt and ptrace_syscall selftests, even in their 64bit variant, use
hard-coded 32bit syscall numbers and call int $0x80. This will fail on
64bit systems with CONFIG_IA32_EMULATION disabled. Therefore, do not build
these tests if we cannot build 32bit binaries (which should be a good
approximation for CONFIG_IA32_EMULATION being enabled).

CC: Dmitry Safonov <dsafonov at virtuozzo.com>
CC: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/Makefile | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 371ae715c506..d744991c0f4f 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -5,16 +5,26 @@ include ../lib.mk
 
 .PHONY: all all_32 all_64 warn_32bit_failure clean
 
-TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
-			check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test ioperm \
+UNAME_M := $(shell uname -m)
+CAN_BUILD_I386 := $(shell ./check_cc.sh $(CC) trivial_32bit_program.c -m32)
+CAN_BUILD_X86_64 := $(shell ./check_cc.sh $(CC) trivial_64bit_program.c)
+
+TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt test_mremap_vdso \
+			check_initial_reg_state sigreturn iopl mpx-mini-test ioperm \
 			protection_keys test_vdso test_vsyscall
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			vdso_restorer
 TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip
+# Some selftests require 32bit support enabled also on 64bit systems
+TARGETS_C_32BIT_NEEDED := ldt_gdt ptrace_syscall
 
-TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
+TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY) $(TARGETS_C_32BIT_NEEDED)
 TARGETS_C_64BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_64BIT_ONLY)
+ifeq ($(CAN_BUILD_I386)$(CAN_BUILD_X86_64),11)
+TARGETS_C_64BIT_ALL += $(TARGETS_C_32BIT_NEEDED)
+endif
+
 BINARIES_32 := $(TARGETS_C_32BIT_ALL:%=%_32)
 BINARIES_64 := $(TARGETS_C_64BIT_ALL:%=%_64)
 
@@ -23,10 +33,6 @@ BINARIES_64 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_64))
 
 CFLAGS := -O2 -g -std=gnu99 -pthread -Wall -no-pie
 
-UNAME_M := $(shell uname -m)
-CAN_BUILD_I386 := $(shell ./check_cc.sh $(CC) trivial_32bit_program.c -m32)
-CAN_BUILD_X86_64 := $(shell ./check_cc.sh $(CC) trivial_64bit_program.c)
-
 define gen-target-rule-32
 $(1) $(1)_32: $(OUTPUT)/$(1)_32
 .PHONY: $(1) $(1)_32
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 5/5] selftests/x86: disable tests requiring 32bit support on pure 64bit systems

[Dominik Brodowski]

The ldt_gdt and ptrace_syscall selftests, even in their 64bit variant, use
hard-coded 32bit syscall numbers and call int $0x80. This will fail on
64bit systems with CONFIG_IA32_EMULATION disabled. Therefore, do not build
these tests if we cannot build 32bit binaries (which should be a good
approximation for CONFIG_IA32_EMULATION being enabled).

CC: Dmitry Safonov <dsafonov at virtuozzo.com>
CC: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
---
 tools/testing/selftests/x86/Makefile | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 371ae715c506..d744991c0f4f 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -5,16 +5,26 @@ include ../lib.mk
 
 .PHONY: all all_32 all_64 warn_32bit_failure clean
 
-TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
-			check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test ioperm \
+UNAME_M := $(shell uname -m)
+CAN_BUILD_I386 := $(shell ./check_cc.sh $(CC) trivial_32bit_program.c -m32)
+CAN_BUILD_X86_64 := $(shell ./check_cc.sh $(CC) trivial_64bit_program.c)
+
+TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt test_mremap_vdso \
+			check_initial_reg_state sigreturn iopl mpx-mini-test ioperm \
 			protection_keys test_vdso test_vsyscall
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			vdso_restorer
 TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip
+# Some selftests require 32bit support enabled also on 64bit systems
+TARGETS_C_32BIT_NEEDED := ldt_gdt ptrace_syscall
 
-TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
+TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY) $(TARGETS_C_32BIT_NEEDED)
 TARGETS_C_64BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_64BIT_ONLY)
+ifeq ($(CAN_BUILD_I386)$(CAN_BUILD_X86_64),11)
+TARGETS_C_64BIT_ALL += $(TARGETS_C_32BIT_NEEDED)
+endif
+
 BINARIES_32 := $(TARGETS_C_32BIT_ALL:%=%_32)
 BINARIES_64 := $(TARGETS_C_64BIT_ALL:%=%_64)
 
@@ -23,10 +33,6 @@ BINARIES_64 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_64))
 
 CFLAGS := -O2 -g -std=gnu99 -pthread -Wall -no-pie
 
-UNAME_M := $(shell uname -m)
-CAN_BUILD_I386 := $(shell ./check_cc.sh $(CC) trivial_32bit_program.c -m32)
-CAN_BUILD_X86_64 := $(shell ./check_cc.sh $(CC) trivial_64bit_program.c)
-
 define gen-target-rule-32
 $(1) $(1)_32: $(OUTPUT)/$(1)_32
 .PHONY: $(1) $(1)_32
-- 
2.16.1

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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[mingo]

* Dominik Brodowski <linux at dominikbrodowski.net> wrote:

> +		char name[128];
> +		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> +			   &start, &end, &r, &x, name) != 5)

So that's a buffer overflow waiting to happen, if a line in 'maps' gets too large, 
right?

Thanks,

	Ingo
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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[Ingo Molnar]

* Dominik Brodowski <linux@dominikbrodowski.net> wrote:

> +		char name[128];
> +		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> +			   &start, &end, &r, &x, name) != 5)

So that's a buffer overflow waiting to happen, if a line in 'maps' gets too large, 
right?

Thanks,

	Ingo
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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[linux]

On Sun, Feb 11, 2018 at 12:21:53PM +0100, Ingo Molnar wrote:
> 
> * Dominik Brodowski <linux at dominikbrodowski.net> wrote:
> 
> > +		char name[128];
> > +		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> > +			   &start, &end, &r, &x, name) != 5)
> 
> So that's a buffer overflow waiting to happen, if a line in 'maps' gets too large, 
> right?

... as does tools/testing/selftests/x86/test_vsyscall.c already now, right?
Will fix both up with an additional patch.

But a more generic question: Is there a quick, easy but reliable test
available in userspace to determine whether
	int $0x80
	vsyscall
is available on a given system, or will cause a segfault?

Thanks,
	Dominik
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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[Dominik Brodowski]

On Sun, Feb 11, 2018@12:21:53PM +0100, Ingo Molnar wrote:
> 
> * Dominik Brodowski <linux@dominikbrodowski.net> wrote:
> 
> > +		char name[128];
> > +		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> > +			   &start, &end, &r, &x, name) != 5)
> 
> So that's a buffer overflow waiting to happen, if a line in 'maps' gets too large, 
> right?

... as does tools/testing/selftests/x86/test_vsyscall.c already now, right?
Will fix both up with an additional patch.

But a more generic question: Is there a quick, easy but reliable test
available in userspace to determine whether
	int $0x80
	vsyscall
is available on a given system, or will cause a segfault?

Thanks,
	Dominik
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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[linux]

On Sun, Feb 11, 2018 at 01:17:14PM +0100, Dominik Brodowski wrote:
> On Sun, Feb 11, 2018 at 12:21:53PM +0100, Ingo Molnar wrote:
> > 
> > * Dominik Brodowski <linux at dominikbrodowski.net> wrote:
> > 
> > > +		char name[128];
> > > +		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> > > +			   &start, &end, &r, &x, name) != 5)
> > 
> > So that's a buffer overflow waiting to happen, if a line in 'maps' gets too large, 
> > right?
> 
> ... as does tools/testing/selftests/x86/test_vsyscall.c already now, right?
> Will fix both up with an additional patch.

Maybe no fix is needed after all: The fgets() call a few lines above
limits "line" to 127 chars max. So "name" can't even get close to 128
chars, right?

	char line[128];
...
	while (fgets(line, sizeof(line), maps)) {

Thanks,
	Dominik
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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[Dominik Brodowski]

On Sun, Feb 11, 2018@01:17:14PM +0100, Dominik Brodowski wrote:
> On Sun, Feb 11, 2018@12:21:53PM +0100, Ingo Molnar wrote:
> > 
> > * Dominik Brodowski <linux@dominikbrodowski.net> wrote:
> > 
> > > +		char name[128];
> > > +		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> > > +			   &start, &end, &r, &x, name) != 5)
> > 
> > So that's a buffer overflow waiting to happen, if a line in 'maps' gets too large, 
> > right?
> 
> ... as does tools/testing/selftests/x86/test_vsyscall.c already now, right?
> Will fix both up with an additional patch.

Maybe no fix is needed after all: The fgets() call a few lines above
limits "line" to 127 chars max. So "name" can't even get close to 128
chars, right?

	char line[128];
...
	while (fgets(line, sizeof(line), maps)) {

Thanks,
	Dominik
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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[mingo]

* Dominik Brodowski <linux at dominikbrodowski.net> wrote:

> On Sun, Feb 11, 2018 at 01:17:14PM +0100, Dominik Brodowski wrote:
> > On Sun, Feb 11, 2018 at 12:21:53PM +0100, Ingo Molnar wrote:
> > > 
> > > * Dominik Brodowski <linux at dominikbrodowski.net> wrote:
> > > 
> > > > +		char name[128];
> > > > +		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> > > > +			   &start, &end, &r, &x, name) != 5)
> > > 
> > > So that's a buffer overflow waiting to happen, if a line in 'maps' gets too large, 
> > > right?
> > 
> > ... as does tools/testing/selftests/x86/test_vsyscall.c already now, right?
> > Will fix both up with an additional patch.
> 
> Maybe no fix is needed after all: The fgets() call a few lines above
> limits "line" to 127 chars max. So "name" can't even get close to 128
> chars, right?
> 
> 	char line[128];
> ...
> 	while (fgets(line, sizeof(line), maps)) {

Yeah, probably - but still, this connection and the sscanf() guarantee is not 
obvious at first sight, so please improve this to derive from the same value 
(define a LINE_MAX size or such), plus maybe add a comment to the sscanf() line 
that this is safe because strlen(name) >= strlen(line).

Thanks,

	Ingo
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[Linux-kselftest-mirror] [PATCH 2/5] selftests/x86: fix vDSO selftest segfault for vsyscall=none

[Ingo Molnar]

* Dominik Brodowski <linux@dominikbrodowski.net> wrote:

> On Sun, Feb 11, 2018@01:17:14PM +0100, Dominik Brodowski wrote:
> > On Sun, Feb 11, 2018@12:21:53PM +0100, Ingo Molnar wrote:
> > > 
> > > * Dominik Brodowski <linux@dominikbrodowski.net> wrote:
> > > 
> > > > +		char name[128];
> > > > +		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> > > > +			   &start, &end, &r, &x, name) != 5)
> > > 
> > > So that's a buffer overflow waiting to happen, if a line in 'maps' gets too large, 
> > > right?
> > 
> > ... as does tools/testing/selftests/x86/test_vsyscall.c already now, right?
> > Will fix both up with an additional patch.
> 
> Maybe no fix is needed after all: The fgets() call a few lines above
> limits "line" to 127 chars max. So "name" can't even get close to 128
> chars, right?
> 
> 	char line[128];
> ...
> 	while (fgets(line, sizeof(line), maps)) {

Yeah, probably - but still, this connection and the sscanf() guarantee is not 
obvious at first sight, so please improve this to derive from the same value 
(define a LINE_MAX size or such), plus maybe add a comment to the sscanf() line 
that this is safe because strlen(name) >= strlen(line).

Thanks,

	Ingo
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[Linux-kselftest-mirror] [PATCH] selftests/x86: clarify that there is no buffer overflow on sscanf usage

[linux]

Suggested-by: Ingo Molnar <mingo at kernel.org>
CC: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>

---

> Yeah, probably - but still, this connection and the sscanf() guarantee is not 
> obvious at first sight, so please improve this to derive from the same value 
> (define a LINE_MAX size or such), plus maybe add a comment to the sscanf() line 
> that this is safe because strlen(name) >= strlen(line).

Sounds reasonable. Patch (which applies on top of the five patches for
selftests/x86 I sent out earlier today) is attached.

Thanks,
	Dominik

diff --git a/tools/testing/selftests/x86/test_vdso.c b/tools/testing/selftests/x86/test_vdso.c
index 558c8207e7b9..7ade625f10ed 100644
--- a/tools/testing/selftests/x86/test_vdso.c
+++ b/tools/testing/selftests/x86/test_vdso.c
@@ -26,6 +26,9 @@
 # endif
 #endif
 
+/* max length of lines in /proc/self/maps - anything longer is skipped here */
+#define MAPS_LINE_LEN 128
+
 int nerrs = 0;
 
 typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
@@ -37,17 +40,19 @@ static void *vsyscall_getcpu(void)
 {
 #ifdef __x86_64__
 	FILE *maps;
-	char line[128];
+	char line[MAPS_LINE_LEN];
 	bool found = false;
 
 	maps = fopen("/proc/self/maps", "r");
 	if (!maps) /* might still be present, but ignore it here, as we test vDSO not vsyscall */
 		return NULL;
 
-	while (fgets(line, sizeof(line), maps)) {
+	while (fgets(line, MAPS_LINE_LEN, maps)) {
 		char r, x;
 		void *start, *end;
-		char name[128];
+		char name[MAPS_LINE_LEN];
+
+		/* sscanf is safe here as strlen(name) >= strlen(line) */
 		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
 			   &start, &end, &r, &x, name) != 5)
 			continue;
diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
index 7a744fa7b786..ee92e4727f18 100644
--- a/tools/testing/selftests/x86/test_vsyscall.c
+++ b/tools/testing/selftests/x86/test_vsyscall.c
@@ -33,6 +33,9 @@
 # endif
 #endif
 
+/* max length of lines in /proc/self/maps - anything longer is skipped here */
+#define MAPS_LINE_LEN 128
+
 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
 		       int flags)
 {
@@ -98,7 +101,7 @@ static int init_vsys(void)
 #ifdef __x86_64__
 	int nerrs = 0;
 	FILE *maps;
-	char line[128];
+	char line[MAPS_LINE_LEN];
 	bool found = false;
 
 	maps = fopen("/proc/self/maps", "r");
@@ -108,10 +111,12 @@ static int init_vsys(void)
 		return 0;
 	}
 
-	while (fgets(line, sizeof(line), maps)) {
+	while (fgets(line, MAPS_LINE_LEN, maps)) {
 		char r, x;
 		void *start, *end;
-		char name[128];
+		char name[MAPS_LINE_LEN];
+
+		/* sscanf is safe here as strlen(name) >= strlen(line) */
 		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
 			   &start, &end, &r, &x, name) != 5)
 			continue;
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[Linux-kselftest-mirror] [PATCH] selftests/x86: clarify that there is no buffer overflow on sscanf usage

[Dominik Brodowski]

Suggested-by: Ingo Molnar <mingo at kernel.org>
CC: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>

---

> Yeah, probably - but still, this connection and the sscanf() guarantee is not 
> obvious at first sight, so please improve this to derive from the same value 
> (define a LINE_MAX size or such), plus maybe add a comment to the sscanf() line 
> that this is safe because strlen(name) >= strlen(line).

Sounds reasonable. Patch (which applies on top of the five patches for
selftests/x86 I sent out earlier today) is attached.

Thanks,
	Dominik

diff --git a/tools/testing/selftests/x86/test_vdso.c b/tools/testing/selftests/x86/test_vdso.c
index 558c8207e7b9..7ade625f10ed 100644
--- a/tools/testing/selftests/x86/test_vdso.c
+++ b/tools/testing/selftests/x86/test_vdso.c
@@ -26,6 +26,9 @@
 # endif
 #endif
 
+/* max length of lines in /proc/self/maps - anything longer is skipped here */
+#define MAPS_LINE_LEN 128
+
 int nerrs = 0;
 
 typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
@@ -37,17 +40,19 @@ static void *vsyscall_getcpu(void)
 {
 #ifdef __x86_64__
 	FILE *maps;
-	char line[128];
+	char line[MAPS_LINE_LEN];
 	bool found = false;
 
 	maps = fopen("/proc/self/maps", "r");
 	if (!maps) /* might still be present, but ignore it here, as we test vDSO not vsyscall */
 		return NULL;
 
-	while (fgets(line, sizeof(line), maps)) {
+	while (fgets(line, MAPS_LINE_LEN, maps)) {
 		char r, x;
 		void *start, *end;
-		char name[128];
+		char name[MAPS_LINE_LEN];
+
+		/* sscanf is safe here as strlen(name) >= strlen(line) */
 		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
 			   &start, &end, &r, &x, name) != 5)
 			continue;
diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
index 7a744fa7b786..ee92e4727f18 100644
--- a/tools/testing/selftests/x86/test_vsyscall.c
+++ b/tools/testing/selftests/x86/test_vsyscall.c
@@ -33,6 +33,9 @@
 # endif
 #endif
 
+/* max length of lines in /proc/self/maps - anything longer is skipped here */
+#define MAPS_LINE_LEN 128
+
 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
 		       int flags)
 {
@@ -98,7 +101,7 @@ static int init_vsys(void)
 #ifdef __x86_64__
 	int nerrs = 0;
 	FILE *maps;
-	char line[128];
+	char line[MAPS_LINE_LEN];
 	bool found = false;
 
 	maps = fopen("/proc/self/maps", "r");
@@ -108,10 +111,12 @@ static int init_vsys(void)
 		return 0;
 	}
 
-	while (fgets(line, sizeof(line), maps)) {
+	while (fgets(line, MAPS_LINE_LEN, maps)) {
 		char r, x;
 		void *start, *end;
-		char name[128];
+		char name[MAPS_LINE_LEN];
+
+		/* sscanf is safe here as strlen(name) >= strlen(line) */
 		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
 			   &start, &end, &r, &x, name) != 5)
 			continue;
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[Linux-kselftest-mirror] [PATCH] selftests/x86: clarify that there is no buffer overflow on sscanf usage

[shuah]

On 02/11/2018 01:59 PM, Dominik Brodowski wrote:
> 
> Suggested-by: Ingo Molnar <mingo at kernel.org>
> CC: Andy Lutomirski <luto at kernel.org>
> Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
> 

Missing commit log. Please add one.

thanks,
-- Shuah

> ---
> 
>> Yeah, probably - but still, this connection and the sscanf() guarantee is not 
>> obvious at first sight, so please improve this to derive from the same value 
>> (define a LINE_MAX size or such), plus maybe add a comment to the sscanf() line 
>> that this is safe because strlen(name) >= strlen(line).
> 
> Sounds reasonable. Patch (which applies on top of the five patches for
> selftests/x86 I sent out earlier today) is attached.
> 
> Thanks,
> 	Dominik
> 
> diff --git a/tools/testing/selftests/x86/test_vdso.c b/tools/testing/selftests/x86/test_vdso.c
> index 558c8207e7b9..7ade625f10ed 100644
> --- a/tools/testing/selftests/x86/test_vdso.c
> +++ b/tools/testing/selftests/x86/test_vdso.c
> @@ -26,6 +26,9 @@
>  # endif
>  #endif
>  
> +/* max length of lines in /proc/self/maps - anything longer is skipped here */
> +#define MAPS_LINE_LEN 128
> +
>  int nerrs = 0;
>  
>  typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
> @@ -37,17 +40,19 @@ static void *vsyscall_getcpu(void)
>  {
>  #ifdef __x86_64__
>  	FILE *maps;
> -	char line[128];
> +	char line[MAPS_LINE_LEN];
>  	bool found = false;
>  
>  	maps = fopen("/proc/self/maps", "r");
>  	if (!maps) /* might still be present, but ignore it here, as we test vDSO not vsyscall */
>  		return NULL;
>  
> -	while (fgets(line, sizeof(line), maps)) {
> +	while (fgets(line, MAPS_LINE_LEN, maps)) {
>  		char r, x;
>  		void *start, *end;
> -		char name[128];
> +		char name[MAPS_LINE_LEN];
> +
> +		/* sscanf is safe here as strlen(name) >= strlen(line) */
>  		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
>  			   &start, &end, &r, &x, name) != 5)
>  			continue;
> diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
> index 7a744fa7b786..ee92e4727f18 100644
> --- a/tools/testing/selftests/x86/test_vsyscall.c
> +++ b/tools/testing/selftests/x86/test_vsyscall.c
> @@ -33,6 +33,9 @@
>  # endif
>  #endif
>  
> +/* max length of lines in /proc/self/maps - anything longer is skipped here */
> +#define MAPS_LINE_LEN 128
> +
>  static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
>  		       int flags)
>  {
> @@ -98,7 +101,7 @@ static int init_vsys(void)
>  #ifdef __x86_64__
>  	int nerrs = 0;
>  	FILE *maps;
> -	char line[128];
> +	char line[MAPS_LINE_LEN];
>  	bool found = false;
>  
>  	maps = fopen("/proc/self/maps", "r");
> @@ -108,10 +111,12 @@ static int init_vsys(void)
>  		return 0;
>  	}
>  
> -	while (fgets(line, sizeof(line), maps)) {
> +	while (fgets(line, MAPS_LINE_LEN, maps)) {
>  		char r, x;
>  		void *start, *end;
> -		char name[128];
> +		char name[MAPS_LINE_LEN];
> +
> +		/* sscanf is safe here as strlen(name) >= strlen(line) */
>  		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
>  			   &start, &end, &r, &x, name) != 5)
>  			continue;
> 
> 

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[Linux-kselftest-mirror] [PATCH] selftests/x86: clarify that there is no buffer overflow on sscanf usage

[Shuah Khan]

On 02/11/2018 01:59 PM, Dominik Brodowski wrote:
> 
> Suggested-by: Ingo Molnar <mingo at kernel.org>
> CC: Andy Lutomirski <luto at kernel.org>
> Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
> 

Missing commit log. Please add one.

thanks,
-- Shuah

> ---
> 
>> Yeah, probably - but still, this connection and the sscanf() guarantee is not 
>> obvious at first sight, so please improve this to derive from the same value 
>> (define a LINE_MAX size or such), plus maybe add a comment to the sscanf() line 
>> that this is safe because strlen(name) >= strlen(line).
> 
> Sounds reasonable. Patch (which applies on top of the five patches for
> selftests/x86 I sent out earlier today) is attached.
> 
> Thanks,
> 	Dominik
> 
> diff --git a/tools/testing/selftests/x86/test_vdso.c b/tools/testing/selftests/x86/test_vdso.c
> index 558c8207e7b9..7ade625f10ed 100644
> --- a/tools/testing/selftests/x86/test_vdso.c
> +++ b/tools/testing/selftests/x86/test_vdso.c
> @@ -26,6 +26,9 @@
>  # endif
>  #endif
>  
> +/* max length of lines in /proc/self/maps - anything longer is skipped here */
> +#define MAPS_LINE_LEN 128
> +
>  int nerrs = 0;
>  
>  typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
> @@ -37,17 +40,19 @@ static void *vsyscall_getcpu(void)
>  {
>  #ifdef __x86_64__
>  	FILE *maps;
> -	char line[128];
> +	char line[MAPS_LINE_LEN];
>  	bool found = false;
>  
>  	maps = fopen("/proc/self/maps", "r");
>  	if (!maps) /* might still be present, but ignore it here, as we test vDSO not vsyscall */
>  		return NULL;
>  
> -	while (fgets(line, sizeof(line), maps)) {
> +	while (fgets(line, MAPS_LINE_LEN, maps)) {
>  		char r, x;
>  		void *start, *end;
> -		char name[128];
> +		char name[MAPS_LINE_LEN];
> +
> +		/* sscanf is safe here as strlen(name) >= strlen(line) */
>  		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
>  			   &start, &end, &r, &x, name) != 5)
>  			continue;
> diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
> index 7a744fa7b786..ee92e4727f18 100644
> --- a/tools/testing/selftests/x86/test_vsyscall.c
> +++ b/tools/testing/selftests/x86/test_vsyscall.c
> @@ -33,6 +33,9 @@
>  # endif
>  #endif
>  
> +/* max length of lines in /proc/self/maps - anything longer is skipped here */
> +#define MAPS_LINE_LEN 128
> +
>  static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
>  		       int flags)
>  {
> @@ -98,7 +101,7 @@ static int init_vsys(void)
>  #ifdef __x86_64__
>  	int nerrs = 0;
>  	FILE *maps;
> -	char line[128];
> +	char line[MAPS_LINE_LEN];
>  	bool found = false;
>  
>  	maps = fopen("/proc/self/maps", "r");
> @@ -108,10 +111,12 @@ static int init_vsys(void)
>  		return 0;
>  	}
>  
> -	while (fgets(line, sizeof(line), maps)) {
> +	while (fgets(line, MAPS_LINE_LEN, maps)) {
>  		char r, x;
>  		void *start, *end;
> -		char name[128];
> +		char name[MAPS_LINE_LEN];
> +
> +		/* sscanf is safe here as strlen(name) >= strlen(line) */
>  		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
>  			   &start, &end, &r, &x, name) != 5)
>  			continue;
> 
> 

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