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forked fromtorvalds/linux

Commitc07a8f8

Browse files
frdesoIngo Molnar
authored and
Ingo Molnar
committed
x86/kprobes: Fix kernel crash when probing .entry_trampoline code
Disable the kprobe probing of the entry trampoline:.entry_trampoline is a code area that is used to ensure page tableisolation between userspace and kernelspace.At the beginning of the execution of the trampoline, we load thekernel's CR3 register. This has the effect of enabling the translationof the kernel virtual addresses to physical addresses. Before thishappens most kernel addresses can not be translated because the runningprocess' CR3 is still used.If a kprobe is placed on the trampoline code before that change of theCR3 register happens the kernel crashes because int3 handling pages arenot accessible.To fix this, add the .entry_trampoline section to the kprobe blacklistto prohibit the probing of code before all the kernel pages areaccessible.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.comCc: mhiramat@kernel.orgLink:http://lkml.kernel.org/r/1520565492-4637-2-git-send-email-francis.deslauriers@efficios.comSigned-off-by: Ingo Molnar <mingo@kernel.org>
1 parentc5b679f commitc07a8f8

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3 files changed

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3 files changed

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‎arch/x86/include/asm/sections.h‎

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@@ -10,6 +10,7 @@ extern struct exception_table_entry __stop___ex_table[];
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#if defined(CONFIG_X86_64)
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externchar__end_rodata_hpage_align[];
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externchar__entry_trampoline_start[],__entry_trampoline_end[];
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#endif
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#endif/* _ASM_X86_SECTIONS_H */

‎arch/x86/kernel/kprobes/core.c‎

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Original file line numberDiff line numberDiff line change
@@ -1168,10 +1168,18 @@ NOKPROBE_SYMBOL(longjmp_break_handler);
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boolarch_within_kprobe_blacklist(unsigned longaddr)
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{
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boolis_in_entry_trampoline_section= false;
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#ifdefCONFIG_X86_64
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is_in_entry_trampoline_section=
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(addr >= (unsigned long)__entry_trampoline_start&&
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addr< (unsigned long)__entry_trampoline_end);
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#endif
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return (addr >= (unsigned long)__kprobes_text_start&&
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addr< (unsigned long)__kprobes_text_end)||
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(addr >= (unsigned long)__entry_text_start&&
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addr< (unsigned long)__entry_text_end);
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addr< (unsigned long)__entry_text_end)||
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is_in_entry_trampoline_section;
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}
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int__initarch_init_kprobes(void)

‎arch/x86/kernel/vmlinux.lds.S‎

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@@ -118,9 +118,11 @@ SECTIONS
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#ifdef CONFIG_X86_64
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. = ALIGN(PAGE_SIZE);
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VMLINUX_SYMBOL(__entry_trampoline_start) = .;
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_entry_trampoline =.;
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*(.entry_trampoline)
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. = ALIGN(PAGE_SIZE);
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VMLINUX_SYMBOL(__entry_trampoline_end) = .;
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ASSERT(. -_entry_trampoline ==PAGE_SIZE,"entry trampoline is too big");
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#endif
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