If syscall_trace_enter_phase1 returns 0, code restores %rax from pt_regs->ax, but should restore it from pt_regs->orig_ax.
The bug crept in because LOAD_ARGS macro was very sublty different from RESTORE_ARGS, it had only two callsites and only this one was using that difference. Signed-off-by: Denys Vlasenko <dvlas...@redhat.com> CC: Linus Torvalds <torva...@linux-foundation.org> CC: Steven Rostedt <rost...@goodmis.org> CC: Ingo Molnar <mi...@kernel.org> CC: Borislav Petkov <b...@alien8.de> CC: "H. Peter Anvin" <h...@zytor.com> CC: Andy Lutomirski <l...@amacapital.net> CC: Oleg Nesterov <o...@redhat.com> CC: Frederic Weisbecker <fweis...@gmail.com> CC: Alexei Starovoitov <a...@plumgrid.com> CC: Will Drewry <w...@chromium.org> CC: Kees Cook <keesc...@chromium.org> CC: x...@kernel.org CC: linux-kernel@vger.kernel.org --- arch/x86/kernel/entry_64.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index da61974..519498d 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -316,7 +316,8 @@ tracesys: call syscall_trace_enter_phase1 test %rax, %rax jnz tracesys_phase2 /* if needed, run the slow path */ - RESTORE_C_REGS /* else restore clobbered regs */ + RESTORE_C_REGS_EXCEPT_RAX /* else restore clobbered regs */ + movq ORIG_RAX(%rsp), %rax jmp system_call_fastpath /* and return to the fast path */ tracesys_phase2: -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/