kernel.git/arch/x86/kernel/traps.c, branch linux-3.18.y

x86/asm/traps: Disable tracing and kprobes in fixup_bad_iret and sync_regs

2015-01-08T18:30:21Z

commit 7ddc6a2199f1da405a2fb68c40db8899b1a8cd87 upstream. These functions can be executed on the int3 stack, so kprobes are dangerous. Tracing is probably a bad idea, too. Fixes: b645af2d5905 ("x86_64, traps: Rework bad_iret") Signed-off-by: Andy Lutomirski Cc: Linus Torvalds Cc: Steven Rostedt Link: http://lkml.kernel.org/r/50e33d26adca60816f3ba968875801652507d0c4.1416870125.git.luto@amacapital.net Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86_64, traps: Rework bad_iret

2014-11-23T21:56:19Z

It's possible for iretq to userspace to fail. This can happen because of a bad CS, SS, or RIP. Historically, we've handled it by fixing up an exception from iretq to land at bad_iret, which pretends that the failed iret frame was really the hardware part of #GP(0) from userspace. To make this work, there's an extra fixup to fudge the gs base into a usable state. This is suboptimal because it loses the original exception. It's also buggy because there's no guarantee that we were on the kernel stack to begin with. For example, if the failing iret happened on return from an NMI, then we'll end up executing general_protection on the NMI stack. This is bad for several reasons, the most immediate of which is that general_protection, as a non-paranoid idtentry, will try to deliver signals and/or schedule from the wrong stack. This patch throws out bad_iret entirely. As a replacement, it augments the existing swapgs fudge into a full-blown iret fixup, mostly written in C. It's should be clearer and more correct. Signed-off-by: Andy Lutomirski Reviewed-by: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds

x86_64, traps: Stop using IST for #SS

2014-11-23T21:56:19Z

On a 32-bit kernel, this has no effect, since there are no IST stacks. On a 64-bit kernel, #SS can only happen in user code, on a failed iret to user space, a canonical violation on access via RSP or RBP, or a genuine stack segment violation in 32-bit kernel code. The first two cases don't need IST, and the latter two cases are unlikely fatal bugs, and promoting them to double faults would be fine. This fixes a bug in which the espfix64 code mishandles a stack segment violation. This saves 4k of memory per CPU and a tiny bit of code. Signed-off-by: Andy Lutomirski Reviewed-by: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds

x86_64, traps: Fix the espfix64 #DF fixup and rewrite it in C

2014-11-23T21:56:18Z

There's nothing special enough about the espfix64 double fault fixup to justify writing it in assembly. Move it to C. This also fixes a bug: if the double fault came from an IST stack, the old asm code would return to a partially uninitialized stack frame. Fixes: 3891a04aafd668686239349ea58f3314ea2af86b Signed-off-by: Andy Lutomirski Reviewed-by: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds

x86/kprobes: Fix build errors and blacklist context_track_user

2014-06-14T07:07:44Z

This essentially reverts commit: ecd50f714c42 ("kprobes, x86: Call exception_enter after kprobes handled") since it causes build errors with CONFIG_CONTEXT_TRACKING and that has been made from misunderstandings; context_track_user_*() don't involve much in interrupt context, it just returns if in_interrupt() is true. Instead of changing the do_debug/int3(), this just adds context_track_user_*() to kprobes blacklist, since those are still can be called right before kprobes handles int3 and debug exceptions, and probing those will cause an infinite loop. Reported-by: Frederic Weisbecker Signed-off-by: Masami Hiramatsu Cc: Borislav Petkov Cc: Kees Cook Cc: Jiri Kosina Cc: Rusty Russell Cc: Steven Rostedt Cc: Seiji Aguchi Cc: Andrew Morton Cc: Kees Cook Link: http://lkml.kernel.org/r/20140614064711.7865.45957.stgit@kbuild-fedora.novalocal Signed-off-by: Ingo Molnar

Merge branch 'perf/urgent' into perf/core, to resolve conflict and to prepare for new patches

2014-06-06T05:55:06Z

Conflicts: arch/x86/kernel/traps.c Signed-off-by: Ingo Molnar

Merge branch 'perf/kprobes' into perf/core

2014-06-05T10:26:50Z

Conflicts: arch/x86/kernel/traps.c The kprobes enhancements are fully cooked, ship them upstream. Signed-off-by: Ingo Molnar

uprobes/x86: Fix the wrong ->si_addr when xol triggers a trap

2014-05-14T11:57:28Z

If the probed insn triggers a trap, ->si_addr = regs->ip is technically correct, but this is not what the signal handler wants; we need to pass the address of the probed insn, not the address of xol slot. Add the new arch-agnostic helper, uprobe_get_trap_addr(), and change fill_trap_info() and math_error() to use it. !CONFIG_UPROBES case in uprobes.h uses a macro to avoid include hell and ensure that it can be compiled even if an architecture doesn't define instruction_pointer(). Test-case: #include #include #include extern void probe_div(void); void sigh(int sig, siginfo_t *info, void *c) { int passed = (info->si_addr == probe_div); printf(passed ? "PASS\n" : "FAIL\n"); _exit(!passed); } int main(void) { struct sigaction sa = { .sa_sigaction = sigh, .sa_flags = SA_SIGINFO, }; sigaction(SIGFPE, &sa, NULL); asm ( "xor %ecx,%ecx\n" ".globl probe_div; probe_div:\n" "idiv %ecx\n" ); return 0; } it fails if probe_div() is probed. Note: show_unhandled_signals users should probably use this helper too, but we need to cleanup them first. Signed-off-by: Oleg Nesterov Reviewed-by: Masami Hiramatsu

x86/traps: Kill DO_ERROR_INFO()

2014-05-14T11:57:28Z

Now that DO_ERROR_INFO() doesn't differ from DO_ERROR() we can remove it and use DO_ERROR() instead. Signed-off-by: Oleg Nesterov

x86/traps: Shift fill_trap_info() from DO_ERROR_INFO() to do_error_trap()

2014-05-14T11:57:27Z

Move the callsite of fill_trap_info() into do_error_trap() and remove the "siginfo_t *info" argument. This obviously breaks DO_ERROR() which passed info == NULL, we simply change fill_trap_info() to return "siginfo_t *" and add the "default" case which returns SEND_SIG_PRIV. Signed-off-by: Oleg Nesterov