From 6ee98ffeea0bc9e072e419497d78697d8afcdd6d Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 25 May 2017 10:57:51 +0200 Subject: [PATCH] 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(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 0651e97..9bef1bb 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; } -- 2.7.4