diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-05-14 19:33:54 -0400 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2014-05-14 19:33:54 -0400 |
| commit | fa81511bb0bbb2b1aace3695ce869da9762624ff (patch) | |
| tree | 4feff999a6217471bc23f997ef77bc492b225ffc | |
| parent | 9844f5462392b53824e8b86726e7c33b5ecbb676 (diff) | |
x86-64, modify_ldt: Make support for 16-bit segments a runtime option
Checkin:
b3b42ac2cbae x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels
disabled 16-bit segments on 64-bit kernels due to an information
leak. However, it does seem that people are genuinely using Wine to
run old 16-bit Windows programs on Linux.
A proper fix for this ("espfix64") is coming in the upcoming merge
window, but as a temporary fix, create a sysctl to allow the
administrator to re-enable support for 16-bit segments.
It adds a "/proc/sys/abi/ldt16" sysctl that defaults to zero (off). If
you hit this issue and care about your old Windows program more than
you care about a kernel stack address information leak, you can do
echo 1 > /proc/sys/abi/ldt16
as root (add it to your startup scripts), and you should be ok.
The sysctl table is only added if you have COMPAT support enabled on
x86-64, but I assume anybody who runs old windows binaries very much
does that ;)
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/CA%2B55aFw9BPoD10U1LfHbOMpHWZkvJTkMcfCs9s3urPr1YyWBxw@mail.gmail.com
Cc: <stable@vger.kernel.org>
| -rw-r--r-- | arch/x86/kernel/ldt.c | 4 | ||||
| -rw-r--r-- | arch/x86/vdso/vdso32-setup.c | 8 |
2 files changed, 11 insertions, 1 deletions
diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c index af1d14a9ebda..dcbbaa165bde 100644 --- a/arch/x86/kernel/ldt.c +++ b/arch/x86/kernel/ldt.c | |||
| @@ -20,6 +20,8 @@ | |||
| 20 | #include <asm/mmu_context.h> | 20 | #include <asm/mmu_context.h> |
| 21 | #include <asm/syscalls.h> | 21 | #include <asm/syscalls.h> |
| 22 | 22 | ||
| 23 | int sysctl_ldt16 = 0; | ||
| 24 | |||
| 23 | #ifdef CONFIG_SMP | 25 | #ifdef CONFIG_SMP |
| 24 | static void flush_ldt(void *current_mm) | 26 | static void flush_ldt(void *current_mm) |
| 25 | { | 27 | { |
| @@ -234,7 +236,7 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) | |||
| 234 | * IRET leaking the high bits of the kernel stack address. | 236 | * IRET leaking the high bits of the kernel stack address. |
| 235 | */ | 237 | */ |
| 236 | #ifdef CONFIG_X86_64 | 238 | #ifdef CONFIG_X86_64 |
| 237 | if (!ldt_info.seg_32bit) { | 239 | if (!ldt_info.seg_32bit && !sysctl_ldt16) { |
| 238 | error = -EINVAL; | 240 | error = -EINVAL; |
| 239 | goto out_unlock; | 241 | goto out_unlock; |
| 240 | } | 242 | } |
diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c index 00348980a3a6..e1f220e3ca68 100644 --- a/arch/x86/vdso/vdso32-setup.c +++ b/arch/x86/vdso/vdso32-setup.c | |||
| @@ -39,6 +39,7 @@ | |||
| 39 | #ifdef CONFIG_X86_64 | 39 | #ifdef CONFIG_X86_64 |
| 40 | #define vdso_enabled sysctl_vsyscall32 | 40 | #define vdso_enabled sysctl_vsyscall32 |
| 41 | #define arch_setup_additional_pages syscall32_setup_pages | 41 | #define arch_setup_additional_pages syscall32_setup_pages |
| 42 | extern int sysctl_ldt16; | ||
| 42 | #endif | 43 | #endif |
| 43 | 44 | ||
| 44 | /* | 45 | /* |
| @@ -249,6 +250,13 @@ static struct ctl_table abi_table2[] = { | |||
| 249 | .mode = 0644, | 250 | .mode = 0644, |
| 250 | .proc_handler = proc_dointvec | 251 | .proc_handler = proc_dointvec |
| 251 | }, | 252 | }, |
| 253 | { | ||
| 254 | .procname = "ldt16", | ||
| 255 | .data = &sysctl_ldt16, | ||
| 256 | .maxlen = sizeof(int), | ||
| 257 | .mode = 0644, | ||
| 258 | .proc_handler = proc_dointvec | ||
| 259 | }, | ||
| 252 | {} | 260 | {} |
| 253 | }; | 261 | }; |
| 254 | 262 | ||