This is a note to let you know that I've just added the patch titled
x86/kprobes: Fix kernel crash when probing .entry_trampoline code
to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: x86-kprobes-fix-kernel-crash-when-probing-.entry_trampoline-code.patch and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From c07a8f8b08ba683ea24f3ac9159f37ae94daf47f Mon Sep 17 00:00:00 2001
From: Francis Deslauriers francis.deslauriers@efficios.com Date: Thu, 8 Mar 2018 22:18:12 -0500 Subject: x86/kprobes: Fix kernel crash when probing .entry_trampoline code
From: Francis Deslauriers francis.deslauriers@efficios.com
commit c07a8f8b08ba683ea24f3ac9159f37ae94daf47f upstream.
Disable the kprobe probing of the entry trampoline:
.entry_trampoline is a code area that is used to ensure page table isolation between userspace and kernelspace.
At the beginning of the execution of the trampoline, we load the kernel's CR3 register. This has the effect of enabling the translation of the kernel virtual addresses to physical addresses. Before this happens most kernel addresses can not be translated because the running process' CR3 is still used.
If a kprobe is placed on the trampoline code before that change of the CR3 register happens the kernel crashes because int3 handling pages are not accessible.
To fix this, add the .entry_trampoline section to the kprobe blacklist to prohibit the probing of code before all the kernel pages are accessible.
Signed-off-by: Francis Deslauriers francis.deslauriers@efficios.com Reviewed-by: Thomas Gleixner tglx@linutronix.de 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: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: mathieu.desnoyers@efficios.com Cc: mhiramat@kernel.org Link: http://lkml.kernel.org/r/1520565492-4637-2-git-send-email-francis.deslaurier... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/include/asm/sections.h | 1 + arch/x86/kernel/kprobes/core.c | 10 +++++++++- arch/x86/kernel/vmlinux.lds.S | 2 ++ 3 files changed, 12 insertions(+), 1 deletion(-)
--- a/arch/x86/include/asm/sections.h +++ b/arch/x86/include/asm/sections.h @@ -10,6 +10,7 @@ extern struct exception_table_entry __st
#if defined(CONFIG_X86_64) extern char __end_rodata_hpage_align[]; +extern char __entry_trampoline_start[], __entry_trampoline_end[]; #endif
#endif /* _ASM_X86_SECTIONS_H */ --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -1168,10 +1168,18 @@ NOKPROBE_SYMBOL(longjmp_break_handler);
bool arch_within_kprobe_blacklist(unsigned long addr) { + bool is_in_entry_trampoline_section = false; + +#ifdef CONFIG_X86_64 + is_in_entry_trampoline_section = + (addr >= (unsigned long)__entry_trampoline_start && + addr < (unsigned long)__entry_trampoline_end); +#endif return (addr >= (unsigned long)__kprobes_text_start && addr < (unsigned long)__kprobes_text_end) || (addr >= (unsigned long)__entry_text_start && - addr < (unsigned long)__entry_text_end); + addr < (unsigned long)__entry_text_end) || + is_in_entry_trampoline_section; }
int __init arch_init_kprobes(void) --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -118,9 +118,11 @@ SECTIONS
#ifdef CONFIG_X86_64 . = ALIGN(PAGE_SIZE); + VMLINUX_SYMBOL(__entry_trampoline_start) = .; _entry_trampoline = .; *(.entry_trampoline) . = ALIGN(PAGE_SIZE); + VMLINUX_SYMBOL(__entry_trampoline_end) = .; ASSERT(. - _entry_trampoline == PAGE_SIZE, "entry trampoline is too big"); #endif
Patches currently in stable-queue which might be from francis.deslauriers@efficios.com are
queue-4.15/x86-kprobes-fix-kernel-crash-when-probing-.entry_trampoline-code.patch