3.16.72-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Andy Lutomirski <[email protected]> commit cb6f64ed5a04036eef07e70b57dd5dd78f2fbcef upstream. In 539f51136500 ("x86/asm/entry/64: Disentangle error_entry/exit gsbase/ebx/usermode code"), I arranged the code slightly wrong -- IRET faults would skip the code path that was intended to execute on all error entries from user mode. Fix it up. While we're at it, make all the labels in error_entry local. This does not fix a bug, but we'll need it, and it slightly shrinks the code. Signed-off-by: Andy Lutomirski <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Kees Cook <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/91e17891e49fa3d61357eadc451529ad48143ee1.1435952415.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> [bwh: Backported to 3.16 as dependency of commit 18ec54fdd6d1 "x86/speculation: Prepare entry code for Spectre v1 swapgs mitigations": - Adjust filename, context] Signed-off-by: Ben Hutchings <[email protected]> --- arch/x86/kernel/entry_64.S | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1445,12 +1445,17 @@ ENTRY(error_entry) */ SWITCH_KERNEL_CR3 testl $3,CS+8(%rsp) - je error_kernelspace + jz .Lerror_kernelspace - /* We entered from user mode */ +.Lerror_entry_from_usermode_swapgs: + /* + * We entered from user mode or we're pretending to have entered + * from user mode due to an IRET fault. + */ SWAPGS -error_entry_done: +.Lerror_entry_from_usermode_after_swapgs: +.Lerror_entry_done: TRACE_IRQS_OFF ret @@ -1460,30 +1465,29 @@ error_entry_done: * truncated RIP for IRET exceptions returning to compat mode. Check * for these here too. */ -error_kernelspace: +.Lerror_kernelspace: leaq native_irq_return_iret(%rip),%rcx cmpq %rcx,RIP+8(%rsp) - je error_bad_iret + je .Lerror_bad_iret movl %ecx,%eax /* zero extend */ cmpq %rax,RIP+8(%rsp) - je bstep_iret + je .Lbstep_iret cmpq $gs_change,RIP+8(%rsp) - jne error_entry_done + jne .Lerror_entry_done /* * hack: gs_change can fail with user gsbase. If this happens, fix up * gsbase and proceed. We'll fix up the exception and land in * gs_change's error handler with kernel gsbase. */ - SWAPGS - jmp error_entry_done + jmp .Lerror_entry_from_usermode_swapgs -bstep_iret: +.Lbstep_iret: /* Fix truncated RIP */ movq %rcx,RIP+8(%rsp) /* fall through */ -error_bad_iret: +.Lerror_bad_iret: /* * We came from an IRET to user mode, so we have user gsbase. * Switch to kernel gsbase: @@ -1497,7 +1501,7 @@ error_bad_iret: mov %rsp,%rdi call fixup_bad_iret mov %rax,%rsp - jmp error_entry_done + jmp .Lerror_entry_from_usermode_after_swapgs CFI_ENDPROC END(error_entry)
