shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-09 20:32:04 +09:00
Code Issues Packages Projects Releases Wiki Activity

x86/asm/entry/64: Remove a bogus 'ret_from_fork' optimization

Browse Source 
commit 956421fbb7 upstream.

'ret_from_fork' checks TIF_IA32 to determine whether 'pt_regs' and
the related state make sense for 'ret_from_sys_call'.  This is
entirely the wrong check.  TS_COMPAT would make a little more
sense, but there's really no point in keeping this optimization
at all.

This fixes a return to the wrong user CS if we came from int
0x80 in a 64-bit task.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/4710be56d76ef994ddf59087aad98c000fbab9a4.1424989793.git.luto@amacapital.net
[ Backported from tip:x86/asm. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Andy Lutomirski
2015-03-05 01:09:44 +01:00
committed by Greg Kroah-Hartman
parent 8dbaea2b3d
commit 22e764ee4b
1 changed files with 8 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
arch/x86/kernel/entry_64.S
View File

@@ -557,11 +557,14 @@ ENTRY(ret_from_fork)
testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread?
jz 1f
testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET
jnz int_ret_from_sys_call
RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
jmp ret_from_sys_call # go to the SYSRET fastpath
/*
* By the time we get here, we have no idea whether our pt_regs,
* ti flags, and ti status came from the 64-bit SYSCALL fast path,
* the slow path, or one of the ia32entry paths.
* Use int_ret_from_sys_call to return, since it can safely handle
* all of the above.
*/
jmp int_ret_from_sys_call
1:
subq $REST_SKIP, %rsp # leave space for volatiles