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x86/ldt: Make modify_ldt() optional

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The modify_ldt syscall exposes a large attack surface and is
unnecessary for modern userspace.  Make it optional.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: security@kernel.org <security@kernel.org>
Cc: xen-devel <xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/a605166a771c343fd64802dece77a903507333bd.1438291540.git.luto@kernel.org
[ Made MATH_EMULATION dependent on MODIFY_LDT_SYSCALL. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski
2015-07-30 14:31:34 -07:00
committed by Ingo Molnar
parent 014dc90b66
commit a5b9e5a2f1
8 changed files with 52 additions and 8 deletions
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4
arch/x86/kernel/cpu/perf_event.c
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@@ -2179,6 +2179,7 @@ static unsigned long get_segment_base(unsigned int segment)
int idx = segment >> 3;
if ((segment & SEGMENT_TI_MASK) == SEGMENT_LDT) {
#ifdef CONFIG_MODIFY_LDT_SYSCALL
struct ldt_struct *ldt;
if (idx > LDT_ENTRIES)
@@ -2190,6 +2191,9 @@ static unsigned long get_segment_base(unsigned int segment)
return 0;
desc = &ldt->entries[idx];
#else
return 0;
#endif
} else {
if (idx > GDT_ENTRIES)
return 0;