From cd88ec2317015f9ae94fa55149bc6f61e1a460e9 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Thu, 13 Aug 2015 16:19:44 -0700 Subject: [PATCH] x86: fix error handling for 32-bit compat out-of-range system call numbers Commit 3f5159a9221f ("x86/asm/entry/32: Update -ENOSYS handling to match the 64-bit logic") broke the ENOSYS handling for the 32-bit compat case. The proper error return value was never loaded into %rax, except if things just happened to go through the audit paths, which ended up reloading the return value. This moves the loading or %rax into the normal system call path, just to make sure the error case triggers it. It's kind of sad, since it adds a useless instruction to reload the register to the fast path, but it's not like that single load from the stack is going to be noticeable. Reported-by: David Drysdale Tested-by: Kees Cook Acked-by: Andy Lutomirski Cc: Denys Vlasenko Cc: Ingo Molnar Signed-off-by: Linus Torvalds --- arch/x86/entry/entry_64_compat.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 5a1844765a7a..a7e257d9cb90 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -140,6 +140,7 @@ sysexit_from_sys_call: */ andl $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS) movl RIP(%rsp), %ecx /* User %eip */ + movq RAX(%rsp), %rax RESTORE_RSI_RDI xorl %edx, %edx /* Do not leak kernel information */ xorq %r8, %r8 @@ -219,7 +220,6 @@ sysexit_from_sys_call: 1: setbe %al /* 1 if error, 0 if not */ movzbl %al, %edi /* zero-extend that into %edi */ call __audit_syscall_exit - movq RAX(%rsp), %rax /* reload syscall return value */ movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %edi DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF @@ -368,6 +368,7 @@ sysretl_from_sys_call: RESTORE_RSI_RDI_RDX movl RIP(%rsp), %ecx movl EFLAGS(%rsp), %r11d + movq RAX(%rsp), %rax xorq %r10, %r10 xorq %r9, %r9 xorq %r8, %r8 -- 2.20.1