x86/asm/entry: Clear EXTRA_REGS for all executable formats
On failure, sys_execve() does not clobber EXTRA_REGS, so we can
just return to userpsace without saving/restoring them.
On success, ELF_PLAT_INIT() in sys_execve() clears all these
registers.
On other executable formats:
- binfmt_flat.c has similar FLAT_PLAT_INIT, but x86 (and everyone
else except sh) doesn't define it.
- binfmt_elf_fdpic.c has ELF_FDPIC_PLAT_INIT, but x86 (and most
others) doesn't define it.
- There are no such hooks in binfmt_aout.c et al. We inherit
EXTRA_REGS from the prior executable.
This inconsistency was not intended.
This change removes SAVE/RESTORE_EXTRA_REGS in stub_execve,
removes register clearing in ELF_PLAT_INIT(),
and instead simply clears them on success in stub_execve.
Run-tested.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1428173719-7637-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 386375d..f4270ff 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -419,25 +419,27 @@
ENTRY(stub_execve)
CFI_STARTPROC
- addq $8, %rsp
- DEFAULT_FRAME 0
- SAVE_EXTRA_REGS
- call sys_execve
- movq %rax,RAX(%rsp)
- RESTORE_EXTRA_REGS
- jmp int_ret_from_sys_call
+ DEFAULT_FRAME 0, 8
+ call sys_execve
+return_from_execve:
+ testl %eax, %eax
+ jz 1f
+ /* exec failed, can use fast SYSRET code path in this case */
+ ret
+1:
+ /* must use IRET code path (pt_regs->cs may have changed) */
+ addq $8, %rsp
+ ZERO_EXTRA_REGS
+ movq %rax,RAX(%rsp)
+ jmp int_ret_from_sys_call
CFI_ENDPROC
END(stub_execve)
ENTRY(stub_execveat)
CFI_STARTPROC
- addq $8, %rsp
- DEFAULT_FRAME 0
- SAVE_EXTRA_REGS
- call sys_execveat
- movq %rax,RAX(%rsp)
- RESTORE_EXTRA_REGS
- jmp int_ret_from_sys_call
+ DEFAULT_FRAME 0, 8
+ call sys_execveat
+ jmp return_from_execve
CFI_ENDPROC
END(stub_execveat)
@@ -472,25 +474,17 @@
ENTRY(stub_x32_execve)
CFI_STARTPROC
- addq $8, %rsp
- DEFAULT_FRAME 0
- SAVE_EXTRA_REGS
- call compat_sys_execve
- movq %rax,RAX(%rsp)
- RESTORE_EXTRA_REGS
- jmp int_ret_from_sys_call
+ DEFAULT_FRAME 0, 8
+ call compat_sys_execve
+ jmp return_from_execve
CFI_ENDPROC
END(stub_x32_execve)
ENTRY(stub_x32_execveat)
CFI_STARTPROC
- addq $8, %rsp
- DEFAULT_FRAME 0
- SAVE_EXTRA_REGS
- call compat_sys_execveat
- movq %rax,RAX(%rsp)
- RESTORE_EXTRA_REGS
- jmp int_ret_from_sys_call
+ DEFAULT_FRAME 0, 8
+ call compat_sys_execveat
+ jmp return_from_execve
CFI_ENDPROC
END(stub_x32_execveat)