From c93f5cf571e7795f97d49ef51b766cf25e328545 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Thu, 25 May 2017 19:38:17 +0900 Subject: kprobes/x86: Fix to set RWX bits correctly before releasing trampoline Fix kprobes to set(recover) RWX bits correctly on trampoline buffer before releasing it. Releasing readonly page to module_memfree() crash the kernel. Without this fix, if kprobes user register a bunch of kprobes in function body (since kprobes on function entry usually use ftrace) and unregister it, kernel hits a BUG and crash. Link: http://lkml.kernel.org/r/149570868652.3518.14120169373590420503.stgit@devbox Signed-off-by: Masami Hiramatsu Fixes: d0381c81c2f7 ("kprobes/x86: Set kprobes pages read-only") Signed-off-by: Steven Rostedt (VMware) --- arch/x86/kernel/kprobes/core.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch') diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 5b2bbfbb3712..6b877807598b 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -52,6 +52,7 @@ #include #include #include +#include #include #include @@ -417,6 +418,14 @@ static void prepare_boost(struct kprobe *p, struct insn *insn) } } +/* Recover page to RW mode before releasing it */ +void free_insn_page(void *page) +{ + set_memory_nx((unsigned long)page & PAGE_MASK, 1); + set_memory_rw((unsigned long)page & PAGE_MASK, 1); + module_memfree(page); +} + static int arch_copy_kprobe(struct kprobe *p) { struct insn insn; -- cgit v1.2.3 From a53276e2826010338478ed94310874001a8097fa Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Fri, 26 May 2017 10:14:11 -0400 Subject: x86/mm/ftrace: Do not bug in early boot on irqs_disabled in cpu_flush_range() With function tracing starting in early bootup and having its trampoline pages being read only, a bug triggered with the following: kernel BUG at arch/x86/mm/pageattr.c:189! invalid opcode: 0000 [#1] SMP Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 4.12.0-rc2-test+ #3 Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014 task: ffffffffb4222500 task.stack: ffffffffb4200000 RIP: 0010:change_page_attr_set_clr+0x269/0x302 RSP: 0000:ffffffffb4203c88 EFLAGS: 00010046 RAX: 0000000000000046 RBX: 0000000000000000 RCX: 00000001b6000000 RDX: ffffffffb4203d40 RSI: 0000000000000000 RDI: ffffffffb4240d60 RBP: ffffffffb4203d18 R08: 00000001b6000000 R09: 0000000000000001 R10: ffffffffb4203aa8 R11: 0000000000000003 R12: ffffffffc029b000 R13: ffffffffb4203d40 R14: 0000000000000001 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff9a639ea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff9a636b384000 CR3: 00000001ea21d000 CR4: 00000000000406b0 Call Trace: change_page_attr_clear+0x1f/0x21 set_memory_ro+0x1e/0x20 arch_ftrace_update_trampoline+0x207/0x21c ? ftrace_caller+0x64/0x64 ? 0xffffffffc029b000 ftrace_startup+0xf4/0x198 register_ftrace_function+0x26/0x3c function_trace_init+0x5e/0x73 tracer_init+0x1e/0x23 tracing_set_tracer+0x127/0x15a register_tracer+0x19b/0x1bc init_function_trace+0x90/0x92 early_trace_init+0x236/0x2b3 start_kernel+0x200/0x3f5 x86_64_start_reservations+0x29/0x2b x86_64_start_kernel+0x17c/0x18f secondary_startup_64+0x9f/0x9f ? secondary_startup_64+0x9f/0x9f Interrupts should not be enabled at this early in the boot process. It is also fine to leave interrupts enabled during this time as there's only one CPU running, and on_each_cpu() means to only run on the current CPU. If early_boot_irqs_disabled is set, it is safe to run cpu_flush_range() with interrupts disabled. Don't trigger a BUG_ON() in that case. Link: http://lkml.kernel.org/r/20170526093717.0be3b849@gandalf.local.home Suggested-by: Thomas Gleixner Signed-off-by: Steven Rostedt (VMware) --- arch/x86/mm/pageattr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 1dcd2be4cce4..c8520b2c62d2 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -186,7 +186,7 @@ static void cpa_flush_range(unsigned long start, int numpages, int cache) unsigned int i, level; unsigned long addr; - BUG_ON(irqs_disabled()); + BUG_ON(irqs_disabled() && !early_boot_irqs_disabled); WARN_ON(PAGE_ALIGN(start) != start); on_each_cpu(__cpa_flush_range, NULL, 1); -- cgit v1.2.3 From 6ee98ffeea0bc9e072e419497d78697d8afcdd6d Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 25 May 2017 10:57:51 +0200 Subject: x86/ftrace: Make sure that ftrace trampolines are not RWX ftrace use module_alloc() to allocate trampoline pages. The mapping of module_alloc() is RWX, which makes sense as the memory is written to right after allocation. But nothing makes these pages RO after writing to them. Add proper set_memory_rw/ro() calls to protect the trampolines after modification. Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1705251056410.1862@nanos Signed-off-by: Thomas Gleixner Signed-off-by: Steven Rostedt (VMware) --- arch/x86/kernel/ftrace.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) (limited to 'arch') diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 0651e974dcb3..9bef1bbeba63 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -689,8 +689,12 @@ static inline void *alloc_tramp(unsigned long size) { return module_alloc(size); } -static inline void tramp_free(void *tramp) +static inline void tramp_free(void *tramp, int size) { + int npages = PAGE_ALIGN(size) >> PAGE_SHIFT; + + set_memory_nx((unsigned long)tramp, npages); + set_memory_rw((unsigned long)tramp, npages); module_memfree(tramp); } #else @@ -699,7 +703,7 @@ static inline void *alloc_tramp(unsigned long size) { return NULL; } -static inline void tramp_free(void *tramp) { } +static inline void tramp_free(void *tramp, int size) { } #endif /* Defined as markers to the end of the ftrace default trampolines */ @@ -771,7 +775,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) /* Copy ftrace_caller onto the trampoline memory */ ret = probe_kernel_read(trampoline, (void *)start_offset, size); if (WARN_ON(ret < 0)) { - tramp_free(trampoline); + tramp_free(trampoline, *tramp_size); return 0; } @@ -797,7 +801,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) /* Are we pointing to the reference? */ if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) { - tramp_free(trampoline); + tramp_free(trampoline, *tramp_size); return 0; } @@ -839,7 +843,7 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops) unsigned long offset; unsigned long ip; unsigned int size; - int ret; + int ret, npages; if (ops->trampoline) { /* @@ -848,11 +852,14 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops) */ if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) return; + npages = PAGE_ALIGN(ops->trampoline_size) >> PAGE_SHIFT; + set_memory_rw(ops->trampoline, npages); } else { ops->trampoline = create_trampoline(ops, &size); if (!ops->trampoline) return; ops->trampoline_size = size; + npages = PAGE_ALIGN(size) >> PAGE_SHIFT; } offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS); @@ -863,6 +870,7 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops) /* Do a safe modify in case the trampoline is executing */ new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); + set_memory_ro(ops->trampoline, npages); /* The update should never fail */ WARN_ON(ret); @@ -939,7 +947,7 @@ void arch_ftrace_trampoline_free(struct ftrace_ops *ops) if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) return; - tramp_free((void *)ops->trampoline); + tramp_free((void *)ops->trampoline, ops->trampoline_size); ops->trampoline = 0; } -- cgit v1.2.3