syscalls/x86: Extend register clearing on syscall entry to lower registers
authorDominik Brodowski <linux@dominikbrodowski.net>
Thu, 5 Apr 2018 09:53:06 +0000 (11:53 +0200)
committerIngo Molnar <mingo@kernel.org>
Thu, 5 Apr 2018 14:59:39 +0000 (16:59 +0200)
commit6dc936f175cc6d12a8eb14d29b87e9238e460383
treeb2a745b9761a0224da7adb2fbd7a40131c347a7b
parentf8781c4a226319fe60e652118b90cf094ccfe747
syscalls/x86: Extend register clearing on syscall entry to lower registers

To reduce the chance that random user space content leaks down the call
chain in registers, also clear lower registers on syscall entry:

For 64-bit syscalls, extend the register clearing in PUSH_AND_CLEAR_REGS
to %dx and %cx. This should not hurt at all, also on the other callers
of that macro. We do not need to clear %rdi and %rsi for syscall entry,
as those registers are used to pass the parameters to do_syscall_64().

For the 32-bit compat syscalls, do_int80_syscall_32() and
do_fast_syscall_32() each only take one parameter. Therefore, extend the
register clearing to %dx, %cx, and %si in entry_SYSCALL_compat and
entry_INT80_compat.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
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: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180405095307.3730-8-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/entry/calling.h
arch/x86/entry/entry_64_compat.S