diff options
| author | Andy Lutomirski | 2017-08-01 07:11:34 -0700 |
|---|---|---|
| committer | Ingo Molnar | 2017-08-10 17:15:13 +0200 |
| commit | 767d035d838f4fd6b5a5bbd7a3f6d293b7f65a49 (patch) | |
| tree | 04a5a48615adfd05d7a7be426f8367aa3c67700a /arch/x86/kernel/process_64.c | |
| parent | af79ded44b7c5eee46b433a9269fcf899372225b (diff) | |
x86/fsgsbase/64: Fully initialize FS and GS state in start_thread_common
execve used to leak FSBASE and GSBASE on AMD CPUs. Fix it.
The security impact of this bug is small but not quite zero -- it
could weaken ASLR when a privileged task execs a less privileged
program, but only if program changed bitness across the exec, or the
child binary was highly unusual or actively malicious. A child
program that was compromised after the exec would not have access to
the leaked base.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chang Seok <chang.seok.bae@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/process_64.c')
| -rw-r--r-- | arch/x86/kernel/process_64.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index e04941fb67fb..d8305ab3d61e 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -228,10 +228,19 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp, unsigned int _cs, unsigned int _ss, unsigned int _ds) { + WARN_ON_ONCE(regs != current_pt_regs()); + + if (static_cpu_has(X86_BUG_NULL_SEG)) { + /* Loading zero below won't clear the base. */ + loadsegment(fs, __USER_DS); + load_gs_index(__USER_DS); + } + loadsegment(fs, 0); loadsegment(es, _ds); loadsegment(ds, _ds); load_gs_index(0); + regs->ip = new_ip; regs->sp = new_sp; regs->cs = _cs; |