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-rw-r--r--debian/patches/features/x86/x86-make-x32-syscall-support-conditional.patch193
1 files changed, 193 insertions, 0 deletions
diff --git a/debian/patches/features/x86/x86-make-x32-syscall-support-conditional.patch b/debian/patches/features/x86/x86-make-x32-syscall-support-conditional.patch
new file mode 100644
index 000000000..62731a997
--- /dev/null
+++ b/debian/patches/features/x86/x86-make-x32-syscall-support-conditional.patch
@@ -0,0 +1,193 @@
+From: Ben Hutchings <ben@decadent.org.uk>
+Date: Mon, 12 Feb 2018 23:59:26 +0000
+Subject: x86: Make x32 syscall support conditional on a kernel parameter
+Bug-Debian: https://bugs.debian.org/708070
+Forwarded: https://lore.kernel.org/lkml/1415245982.3398.53.camel@decadent.org.uk/T/#u
+
+Enabling x32 in the standard amd64 kernel would increase its attack
+surface while provide no benefit to the vast majority of its users.
+No-one seems interested in regularly checking for vulnerabilities
+specific to x32 (at least no-one with a white hat).
+
+Still, adding another flavour just to turn on x32 seems wasteful. And
+the only differences on syscall entry are a few instructions that mask
+out the x32 flag and compare the syscall number.
+
+Use a static key to control whether x32 syscalls are really enabled, a
+Kconfig parameter to set its default value and a kernel parameter
+"syscall.x32" to change it at boot time.
+
+Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
+---
+ .../admin-guide/kernel-parameters.txt | 4 ++
+ arch/x86/Kconfig | 8 ++++
+ arch/x86/entry/common.c | 3 +-
+ arch/x86/entry/syscall_64.c | 46 +++++++++++++++++++
+ arch/x86/include/asm/elf.h | 6 ++-
+ arch/x86/include/asm/syscall.h | 13 ++++++
+ 6 files changed, 78 insertions(+), 2 deletions(-)
+
+Index: debian-kernel/Documentation/admin-guide/kernel-parameters.txt
+===================================================================
+--- debian-kernel.orig/Documentation/admin-guide/kernel-parameters.txt
++++ debian-kernel/Documentation/admin-guide/kernel-parameters.txt
+@@ -5000,6 +5000,10 @@
+ later by a loaded module cannot be set this way.
+ Example: sysctl.vm.swappiness=40
+
++ syscall.x32= [KNL,x86_64] Enable/disable use of x32 syscalls on
++ an x86_64 kernel where CONFIG_X86_X32 is enabled.
++ Default depends on CONFIG_X86_X32_DISABLED.
++
+ sysfs.deprecated=0|1 [KNL]
+ Enable/disable old style sysfs layout for old udev
+ on older distributions. When this option is enabled
+Index: debian-kernel/arch/x86/Kconfig
+===================================================================
+--- debian-kernel.orig/arch/x86/Kconfig
++++ debian-kernel/arch/x86/Kconfig
+@@ -2888,6 +2888,14 @@ config COMPAT_32
+ select HAVE_UID16
+ select OLD_SIGSUSPEND3
+
++config X86_X32_DISABLED
++ bool "x32 ABI disabled by default"
++ depends on X86_X32
++ default n
++ help
++ Disable the x32 ABI unless explicitly enabled using the
++ kernel paramter "syscall.x32=y".
++
+ config COMPAT
+ def_bool y
+ depends on IA32_EMULATION || X86_X32
+Index: debian-kernel/arch/x86/entry/common.c
+===================================================================
+--- debian-kernel.orig/arch/x86/entry/common.c
++++ debian-kernel/arch/x86/entry/common.c
+@@ -383,7 +383,8 @@ __visible noinstr void do_syscall_64(uns
+ nr = array_index_nospec(nr, NR_syscalls);
+ regs->ax = sys_call_table[nr](regs);
+ #ifdef CONFIG_X86_X32_ABI
+- } else if (likely((nr & __X32_SYSCALL_BIT) &&
++ } else if (x32_enabled &&
++ likely((nr & __X32_SYSCALL_BIT) &&
+ (nr & ~__X32_SYSCALL_BIT) < X32_NR_syscalls)) {
+ nr = array_index_nospec(nr & ~__X32_SYSCALL_BIT,
+ X32_NR_syscalls);
+Index: debian-kernel/arch/x86/entry/syscall_x32.c
+===================================================================
+--- debian-kernel.orig/arch/x86/entry/syscall_x32.c
++++ debian-kernel/arch/x86/entry/syscall_x32.c
+@@ -4,6 +4,9 @@
+ #include <linux/linkage.h>
+ #include <linux/sys.h>
+ #include <linux/cache.h>
++#include <linux/moduleparam.h>
++#undef MODULE_PARAM_PREFIX
++#define MODULE_PARAM_PREFIX "syscall."
+ #include <linux/syscalls.h>
+ #include <asm/unistd.h>
+ #include <asm/syscall.h>
+@@ -27,3 +30,46 @@ asmlinkage const sys_call_ptr_t x32_sys_
+ [0 ... __NR_x32_syscall_max] = &__x64_sys_ni_syscall,
+ #include <asm/syscalls_64.h>
+ };
++
++/* Maybe enable x32 syscalls */
++
++#if defined(CONFIG_X86_X32_DISABLED)
++DEFINE_STATIC_KEY_FALSE(x32_enabled_skey);
++#else
++DEFINE_STATIC_KEY_TRUE(x32_enabled_skey);
++#endif
++
++static int __init x32_param_set(const char *val, const struct kernel_param *p)
++{
++ bool enabled;
++ int ret;
++
++ ret = kstrtobool(val, &enabled);
++ if (ret)
++ return ret;
++ if (IS_ENABLED(CONFIG_X86_X32_DISABLED)) {
++ if (enabled) {
++ static_key_enable(&x32_enabled_skey.key);
++ pr_info("Enabled x32 syscalls\n");
++ }
++ } else {
++ if (!enabled) {
++ static_key_disable(&x32_enabled_skey.key);
++ pr_info("Disabled x32 syscalls\n");
++ }
++ }
++ return 0;
++}
++
++static int x32_param_get(char *buffer, const struct kernel_param *p)
++{
++ return sprintf(buffer, "%c\n",
++ static_key_enabled(&x32_enabled_skey) ? 'Y' : 'N');
++}
++
++static const struct kernel_param_ops x32_param_ops = {
++ .set = x32_param_set,
++ .get = x32_param_get,
++};
++
++arch_param_cb(x32, &x32_param_ops, NULL, 0444);
+Index: debian-kernel/arch/x86/include/asm/elf.h
+===================================================================
+--- debian-kernel.orig/arch/x86/include/asm/elf.h
++++ debian-kernel/arch/x86/include/asm/elf.h
+@@ -11,6 +11,9 @@
+ #include <asm/user.h>
+ #include <asm/auxvec.h>
+ #include <asm/fsgsbase.h>
++#ifndef COMPILE_OFFSETS /* avoid a circular dependency on asm-offsets.h */
++#include <asm/syscall.h>
++#endif
+
+ typedef unsigned long elf_greg_t;
+
+@@ -163,7 +166,8 @@ do { \
+
+ #define compat_elf_check_arch(x) \
+ (elf_check_arch_ia32(x) || \
+- (IS_ENABLED(CONFIG_X86_X32_ABI) && (x)->e_machine == EM_X86_64))
++ (IS_ENABLED(CONFIG_X86_X32_ABI) && x32_enabled && \
++ (x)->e_machine == EM_X86_64))
+
+ #if __USER32_DS != __USER_DS
+ # error "The following code assumes __USER32_DS == __USER_DS"
+Index: debian-kernel/arch/x86/include/asm/syscall.h
+===================================================================
+--- debian-kernel.orig/arch/x86/include/asm/syscall.h
++++ debian-kernel/arch/x86/include/asm/syscall.h
+@@ -13,6 +13,7 @@
+ #include <uapi/linux/audit.h>
+ #include <linux/sched.h>
+ #include <linux/err.h>
++#include <linux/jump_label.h>
+ #include <asm/thread_info.h> /* for TS_COMPAT */
+ #include <asm/unistd.h>
+
+@@ -31,6 +32,18 @@ extern const sys_call_ptr_t ia32_sys_cal
+ extern const sys_call_ptr_t x32_sys_call_table[];
+ #endif
+
++#if defined(CONFIG_X86_X32_ABI)
++#if defined(CONFIG_X86_X32_DISABLED)
++DECLARE_STATIC_KEY_FALSE(x32_enabled_skey);
++#define x32_enabled static_branch_unlikely(&x32_enabled_skey)
++#else
++DECLARE_STATIC_KEY_TRUE(x32_enabled_skey);
++#define x32_enabled static_branch_likely(&x32_enabled_skey)
++#endif
++#else
++#define x32_enabled 0
++#endif
++
+ /*
+ * Only the low 32 bits of orig_ax are meaningful, so we return int.
+ * This importantly ignores the high bits on 64-bit, so comparisons
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-16 05:59:08 +0000