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-rw-r--r--Documentation/admin-guide/hw-vuln/spectre.rst86
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt12
-rw-r--r--arch/x86/entry/syscall_32.c10
-rw-r--r--arch/x86/entry/syscall_64.c9
-rw-r--r--arch/x86/entry/syscall_x32.c7
-rw-r--r--arch/x86/entry/syscalls/syscall_32.tbl6
-rw-r--r--arch/x86/entry/syscalls/syscall_64.tbl6
-rw-r--r--arch/x86/kernel/cpu/bugs.c16
-rw-r--r--arch/x86/um/sys_call_table_32.c10
-rw-r--r--arch/x86/um/sys_call_table_64.c11
-rwxr-xr-xscripts/syscalltbl.sh18
-rw-r--r--tools/objtool/noreturns.h4
12 files changed, 86 insertions, 109 deletions
diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst
index 25a04cda4c2c..132e0bc6007e 100644
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -592,85 +592,19 @@ Spectre variant 2
Mitigation control on the kernel command line
---------------------------------------------
-Spectre variant 2 mitigation can be disabled or force enabled at the
-kernel command line.
+In general the kernel selects reasonable default mitigations for the
+current CPU.
- nospectre_v1
+Spectre default mitigations can be disabled or changed at the kernel
+command line with the following options:
- [X86,PPC] Disable mitigations for Spectre Variant 1
- (bounds check bypass). With this option data leaks are
- possible in the system.
+ - nospectre_v1
+ - nospectre_v2
+ - spectre_v2={option}
+ - spectre_v2_user={option}
+ - spectre_bhi={option}
- nospectre_v2
-
- [X86] Disable all mitigations for the Spectre variant 2
- (indirect branch prediction) vulnerability. System may
- allow data leaks with this option, which is equivalent
- to spectre_v2=off.
-
-
- spectre_v2=
-
- [X86] Control mitigation of Spectre variant 2
- (indirect branch speculation) vulnerability.
- The default operation protects the kernel from
- user space attacks.
-
- on
- unconditionally enable, implies
- spectre_v2_user=on
- off
- unconditionally disable, implies
- spectre_v2_user=off
- auto
- kernel detects whether your CPU model is
- vulnerable
-
- Selecting 'on' will, and 'auto' may, choose a
- mitigation method at run time according to the
- CPU, the available microcode, the setting of the
- CONFIG_MITIGATION_RETPOLINE configuration option,
- and the compiler with which the kernel was built.
-
- Selecting 'on' will also enable the mitigation
- against user space to user space task attacks.
-
- Selecting 'off' will disable both the kernel and
- the user space protections.
-
- Specific mitigations can also be selected manually:
-
- retpoline auto pick between generic,lfence
- retpoline,generic Retpolines
- retpoline,lfence LFENCE; indirect branch
- retpoline,amd alias for retpoline,lfence
- eibrs Enhanced/Auto IBRS
- eibrs,retpoline Enhanced/Auto IBRS + Retpolines
- eibrs,lfence Enhanced/Auto IBRS + LFENCE
- ibrs use IBRS to protect kernel
-
- Not specifying this option is equivalent to
- spectre_v2=auto.
-
- In general the kernel by default selects
- reasonable mitigations for the current CPU. To
- disable Spectre variant 2 mitigations, boot with
- spectre_v2=off. Spectre variant 1 mitigations
- cannot be disabled.
-
- spectre_bhi=
-
- [X86] Control mitigation of Branch History Injection
- (BHI) vulnerability. This setting affects the deployment
- of the HW BHI control and the SW BHB clearing sequence.
-
- on
- (default) Enable the HW or SW mitigation as
- needed.
- off
- Disable the mitigation.
-
-For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt
+For more details on the available options, refer to Documentation/admin-guide/kernel-parameters.txt
Mitigation selection guide
--------------------------
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9faf5edd4c82..9d207d53f9b7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6125,9 +6125,15 @@
deployment of the HW BHI control and the SW BHB
clearing sequence.
- on - (default) Enable the HW or SW mitigation
- as needed.
- off - Disable the mitigation.
+ on - (default) Enable the HW or SW mitigation as
+ needed. This protects the kernel from
+ both syscalls and VMs.
+ vmexit - On systems which don't have the HW mitigation
+ available, enable the SW mitigation on vmexit
+ ONLY. On such systems, the host kernel is
+ protected from VM-originated BHI attacks, but
+ may still be vulnerable to syscall attacks.
+ off - Disable the mitigation.
spectre_v2= [X86,EARLY] Control mitigation of Spectre variant 2
(indirect branch speculation) vulnerability.
diff --git a/arch/x86/entry/syscall_32.c b/arch/x86/entry/syscall_32.c
index c2235bae17ef..8cc9950d7104 100644
--- a/arch/x86/entry/syscall_32.c
+++ b/arch/x86/entry/syscall_32.c
@@ -14,9 +14,12 @@
#endif
#define __SYSCALL(nr, sym) extern long __ia32_##sym(const struct pt_regs *);
-
+#define __SYSCALL_NORETURN(nr, sym) extern long __noreturn __ia32_##sym(const struct pt_regs *);
#include <asm/syscalls_32.h>
-#undef __SYSCALL
+#undef __SYSCALL
+
+#undef __SYSCALL_NORETURN
+#define __SYSCALL_NORETURN __SYSCALL
/*
* The sys_call_table[] is no longer used for system calls, but
@@ -28,11 +31,10 @@
const sys_call_ptr_t sys_call_table[] = {
#include <asm/syscalls_32.h>
};
-#undef __SYSCALL
+#undef __SYSCALL
#endif
#define __SYSCALL(nr, sym) case nr: return __ia32_##sym(regs);
-
long ia32_sys_call(const struct pt_regs *regs, unsigned int nr)
{
switch (nr) {
diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c
index 33b3f09e6f15..ba8354424860 100644
--- a/arch/x86/entry/syscall_64.c
+++ b/arch/x86/entry/syscall_64.c
@@ -8,8 +8,12 @@
#include <asm/syscall.h>
#define __SYSCALL(nr, sym) extern long __x64_##sym(const struct pt_regs *);
+#define __SYSCALL_NORETURN(nr, sym) extern long __noreturn __x64_##sym(const struct pt_regs *);
#include <asm/syscalls_64.h>
-#undef __SYSCALL
+#undef __SYSCALL
+
+#undef __SYSCALL_NORETURN
+#define __SYSCALL_NORETURN __SYSCALL
/*
* The sys_call_table[] is no longer used for system calls, but
@@ -20,10 +24,9 @@
const sys_call_ptr_t sys_call_table[] = {
#include <asm/syscalls_64.h>
};
-#undef __SYSCALL
+#undef __SYSCALL
#define __SYSCALL(nr, sym) case nr: return __x64_##sym(regs);
-
long x64_sys_call(const struct pt_regs *regs, unsigned int nr)
{
switch (nr) {
diff --git a/arch/x86/entry/syscall_x32.c b/arch/x86/entry/syscall_x32.c
index 03de4a932131..fb77908f44f3 100644
--- a/arch/x86/entry/syscall_x32.c
+++ b/arch/x86/entry/syscall_x32.c
@@ -8,11 +8,14 @@
#include <asm/syscall.h>
#define __SYSCALL(nr, sym) extern long __x64_##sym(const struct pt_regs *);
+#define __SYSCALL_NORETURN(nr, sym) extern long __noreturn __x64_##sym(const struct pt_regs *);
#include <asm/syscalls_x32.h>
-#undef __SYSCALL
+#undef __SYSCALL
-#define __SYSCALL(nr, sym) case nr: return __x64_##sym(regs);
+#undef __SYSCALL_NORETURN
+#define __SYSCALL_NORETURN __SYSCALL
+#define __SYSCALL(nr, sym) case nr: return __x64_##sym(regs);
long x32_sys_call(const struct pt_regs *regs, unsigned int nr)
{
switch (nr) {
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index ecf5f146783f..534c74b14fab 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -3,7 +3,7 @@
# 32-bit system call numbers and entry vectors
#
# The format is:
-# <number> <abi> <name> <entry point> <compat entry point>
+# <number> <abi> <name> <entry point> [<compat entry point> [noreturn]]
#
# The __ia32_sys and __ia32_compat_sys stubs are created on-the-fly for
# sys_*() system calls and compat_sys_*() compat system calls if
@@ -13,7 +13,7 @@
# The abi is always "i386" for this file.
#
0 i386 restart_syscall sys_restart_syscall
-1 i386 exit sys_exit
+1 i386 exit sys_exit - noreturn
2 i386 fork sys_fork
3 i386 read sys_read
4 i386 write sys_write
@@ -264,7 +264,7 @@
249 i386 io_cancel sys_io_cancel
250 i386 fadvise64 sys_ia32_fadvise64
# 251 is available for reuse (was briefly sys_set_zone_reclaim)
-252 i386 exit_group sys_exit_group
+252 i386 exit_group sys_exit_group - noreturn
253 i386 lookup_dcookie
254 i386 epoll_create sys_epoll_create
255 i386 epoll_ctl sys_epoll_ctl
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 129bdd475cf0..097e5a18db52 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -3,7 +3,7 @@
# 64-bit system call numbers and entry vectors
#
# The format is:
-# <number> <abi> <name> <entry point>
+# <number> <abi> <name> <entry point> [<compat entry point> [noreturn]]
#
# The __x64_sys_*() stubs are created on-the-fly for sys_*() system calls
#
@@ -69,7 +69,7 @@
57 common fork sys_fork
58 common vfork sys_vfork
59 64 execve sys_execve
-60 common exit sys_exit
+60 common exit sys_exit - noreturn
61 common wait4 sys_wait4
62 common kill sys_kill
63 common uname sys_newuname
@@ -240,7 +240,7 @@
228 common clock_gettime sys_clock_gettime
229 common clock_getres sys_clock_getres
230 common clock_nanosleep sys_clock_nanosleep
-231 common exit_group sys_exit_group
+231 common exit_group sys_exit_group - noreturn
232 common epoll_wait sys_epoll_wait
233 common epoll_ctl sys_epoll_ctl
234 common tgkill sys_tgkill
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b6f927f6c567..45675da354f3 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1625,6 +1625,7 @@ static bool __init spec_ctrl_bhi_dis(void)
enum bhi_mitigations {
BHI_MITIGATION_OFF,
BHI_MITIGATION_ON,
+ BHI_MITIGATION_VMEXIT_ONLY,
};
static enum bhi_mitigations bhi_mitigation __ro_after_init =
@@ -1639,6 +1640,8 @@ static int __init spectre_bhi_parse_cmdline(char *str)
bhi_mitigation = BHI_MITIGATION_OFF;
else if (!strcmp(str, "on"))
bhi_mitigation = BHI_MITIGATION_ON;
+ else if (!strcmp(str, "vmexit"))
+ bhi_mitigation = BHI_MITIGATION_VMEXIT_ONLY;
else
pr_err("Ignoring unknown spectre_bhi option (%s)", str);
@@ -1659,19 +1662,22 @@ static void __init bhi_select_mitigation(void)
return;
}
+ /* Mitigate in hardware if supported */
if (spec_ctrl_bhi_dis())
return;
if (!IS_ENABLED(CONFIG_X86_64))
return;
- /* Mitigate KVM by default */
- setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT);
- pr_info("Spectre BHI mitigation: SW BHB clearing on vm exit\n");
+ if (bhi_mitigation == BHI_MITIGATION_VMEXIT_ONLY) {
+ pr_info("Spectre BHI mitigation: SW BHB clearing on VM exit only\n");
+ setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT);
+ return;
+ }
- /* Mitigate syscalls when the mitigation is forced =on */
+ pr_info("Spectre BHI mitigation: SW BHB clearing on syscall and VM exit\n");
setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP);
- pr_info("Spectre BHI mitigation: SW BHB clearing on syscall\n");
+ setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT);
}
static void __init spectre_v2_select_mitigation(void)
diff --git a/arch/x86/um/sys_call_table_32.c b/arch/x86/um/sys_call_table_32.c
index 89df5d89d664..51655133eee3 100644
--- a/arch/x86/um/sys_call_table_32.c
+++ b/arch/x86/um/sys_call_table_32.c
@@ -9,6 +9,10 @@
#include <linux/cache.h>
#include <asm/syscall.h>
+extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long,
+ unsigned long, unsigned long,
+ unsigned long, unsigned long);
+
/*
* Below you can see, in terms of #define's, the differences between the x86-64
* and the UML syscall table.
@@ -22,15 +26,13 @@
#define sys_vm86 sys_ni_syscall
#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native)
+#define __SYSCALL_NORETURN __SYSCALL
#define __SYSCALL(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
#include <asm/syscalls_32.h>
+#undef __SYSCALL
-#undef __SYSCALL
#define __SYSCALL(nr, sym) sym,
-
-extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
-
const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
#include <asm/syscalls_32.h>
};
diff --git a/arch/x86/um/sys_call_table_64.c b/arch/x86/um/sys_call_table_64.c
index b0b4cfd2308c..943d414f2109 100644
--- a/arch/x86/um/sys_call_table_64.c
+++ b/arch/x86/um/sys_call_table_64.c
@@ -9,6 +9,10 @@
#include <linux/cache.h>
#include <asm/syscall.h>
+extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long,
+ unsigned long, unsigned long,
+ unsigned long, unsigned long);
+
/*
* Below you can see, in terms of #define's, the differences between the x86-64
* and the UML syscall table.
@@ -18,14 +22,13 @@
#define sys_iopl sys_ni_syscall
#define sys_ioperm sys_ni_syscall
+#define __SYSCALL_NORETURN __SYSCALL
+
#define __SYSCALL(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
#include <asm/syscalls_64.h>
+#undef __SYSCALL
-#undef __SYSCALL
#define __SYSCALL(nr, sym) sym,
-
-extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
-
const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
#include <asm/syscalls_64.h>
};
diff --git a/scripts/syscalltbl.sh b/scripts/syscalltbl.sh
index 6abe143889ef..6a903b87a7c2 100755
--- a/scripts/syscalltbl.sh
+++ b/scripts/syscalltbl.sh
@@ -54,7 +54,7 @@ nxt=0
grep -E "^[0-9]+[[:space:]]+$abis" "$infile" | {
- while read nr abi name native compat ; do
+ while read nr abi name native compat noreturn; do
if [ $nxt -gt $nr ]; then
echo "error: $infile: syscall table is not sorted or duplicates the same syscall number" >&2
@@ -66,7 +66,21 @@ grep -E "^[0-9]+[[:space:]]+$abis" "$infile" | {
nxt=$((nxt + 1))
done
- if [ -n "$compat" ]; then
+ if [ "$compat" = "-" ]; then
+ unset compat
+ fi
+
+ if [ -n "$noreturn" ]; then
+ if [ "$noreturn" != "noreturn" ]; then
+ echo "error: $infile: invalid string \"$noreturn\" in 'noreturn' column"
+ exit 1
+ fi
+ if [ -n "$compat" ]; then
+ echo "__SYSCALL_COMPAT_NORETURN($nr, $native, $compat)"
+ else
+ echo "__SYSCALL_NORETURN($nr, $native)"
+ fi
+ elif [ -n "$compat" ]; then
echo "__SYSCALL_WITH_COMPAT($nr, $native, $compat)"
elif [ -n "$native" ]; then
echo "__SYSCALL($nr, $native)"
diff --git a/tools/objtool/noreturns.h b/tools/objtool/noreturns.h
index 7ebf29c91184..1e8141ef1b15 100644
--- a/tools/objtool/noreturns.h
+++ b/tools/objtool/noreturns.h
@@ -7,12 +7,16 @@
* Yes, this is unfortunate. A better solution is in the works.
*/
NORETURN(__fortify_panic)
+NORETURN(__ia32_sys_exit)
+NORETURN(__ia32_sys_exit_group)
NORETURN(__kunit_abort)
NORETURN(__module_put_and_kthread_exit)
NORETURN(__reiserfs_panic)
NORETURN(__stack_chk_fail)
NORETURN(__tdx_hypercall_failed)
NORETURN(__ubsan_handle_builtin_unreachable)
+NORETURN(__x64_sys_exit)
+NORETURN(__x64_sys_exit_group)
NORETURN(arch_cpu_idle_dead)
NORETURN(bch2_trans_in_restart_error)
NORETURN(bch2_trans_restart_error)
generated by cgit v1.2.3-58-ga151 (git 2.39.0) at 2024-11-21 18:05:50 +0000