From: Alexey Dobriyan adobriyan@gmail.com
commit 5316a017d093f644675a56523bcf5787ba8f4fef upstream.
vsyscall detection code uses direct call to the beginning of the vsyscall page:
asm ("call %P0" :: "i" (0xffffffffff600000))
It generates "call rel32" instruction but it is not relocated if binary is PIE, so binary segfaults into random userspace address and vsyscall page status is detected incorrectly.
Do more direct:
asm ("call *%rax")
which doesn't do need any relocaltions.
Mark g_vsyscall as volatile for a good measure, I didn't find instruction setting it to 0. Now the code is obviously correct:
xor eax, eax mov rdi, rbp mov rsi, rbp mov DWORD PTR [rip+0x2d15], eax # g_vsyscall = 0 mov rax, 0xffffffffff600000 call rax mov DWORD PTR [rip+0x2d02], 1 # g_vsyscall = 1 mov eax, DWORD PTR ds:0xffffffffff600000 mov DWORD PTR [rip+0x2cf1], 2 # g_vsyscall = 2 mov edi, [rip+0x2ceb] # exit(g_vsyscall) call exit
Note: fixed proc-empty-vm test oopses 5.19.0-28-generic kernel but this is separate story.
Link: https://lkml.kernel.org/r/Y7h2xvzKLg36DSq8@p183 Fixes: 5bc73bb3451b9 ("proc: test how it holds up with mapping'less process") Signed-off-by: Alexey Dobriyan adobriyan@gmail.com Reported-by: Mirsad Goran Todorovac mirsad.todorovac@alu.unizg.hr Tested-by: Mirsad Goran Todorovac mirsad.todorovac@alu.unizg.hr Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/testing/selftests/proc/proc-empty-vm.c | 12 +++++++----- tools/testing/selftests/proc/proc-pid-vm.c | 9 +++++---- 2 files changed, 12 insertions(+), 9 deletions(-)
diff --git a/tools/testing/selftests/proc/proc-empty-vm.c b/tools/testing/selftests/proc/proc-empty-vm.c index d95b1cb43d9d..7588428b8fcd 100644 --- a/tools/testing/selftests/proc/proc-empty-vm.c +++ b/tools/testing/selftests/proc/proc-empty-vm.c @@ -25,6 +25,7 @@ #undef NDEBUG #include <assert.h> #include <errno.h> +#include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> @@ -41,7 +42,7 @@ * 1: vsyscall VMA is --xp vsyscall=xonly * 2: vsyscall VMA is r-xp vsyscall=emulate */ -static int g_vsyscall; +static volatile int g_vsyscall; static const char *g_proc_pid_maps_vsyscall; static const char *g_proc_pid_smaps_vsyscall;
@@ -147,11 +148,12 @@ static void vsyscall(void)
g_vsyscall = 0; /* gettimeofday(NULL, NULL); */ + uint64_t rax = 0xffffffffff600000; asm volatile ( - "call %P0" - : - : "i" (0xffffffffff600000), "D" (NULL), "S" (NULL) - : "rax", "rcx", "r11" + "call *%[rax]" + : [rax] "+a" (rax) + : "D" (NULL), "S" (NULL) + : "rcx", "r11" );
g_vsyscall = 1; diff --git a/tools/testing/selftests/proc/proc-pid-vm.c b/tools/testing/selftests/proc/proc-pid-vm.c index 69551bfa215c..cacbd2a4aec9 100644 --- a/tools/testing/selftests/proc/proc-pid-vm.c +++ b/tools/testing/selftests/proc/proc-pid-vm.c @@ -257,11 +257,12 @@ static void vsyscall(void)
g_vsyscall = 0; /* gettimeofday(NULL, NULL); */ + uint64_t rax = 0xffffffffff600000; asm volatile ( - "call %P0" - : - : "i" (0xffffffffff600000), "D" (NULL), "S" (NULL) - : "rax", "rcx", "r11" + "call *%[rax]" + : [rax] "+a" (rax) + : "D" (NULL), "S" (NULL) + : "rcx", "r11" );
g_vsyscall = 1;