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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 <tglx@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Thomas Gleixner 2017-05-25 10:57:51 +02:00 committed by Steven Rostedt (VMware)
parent a53276e282
commit 6ee98ffeea
1 changed files with 14 additions and 6 deletions
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20
arch/x86/kernel/ftrace.c
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@ -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;
}