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x86/kprobes: Verify stack frame on kretprobe

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commit 3ff9c075cc767b3060bdac12da72fc94dd7da1b8 upstream.

Verify the stack frame pointer on kretprobe trampoline handler,
If the stack frame pointer does not match, it skips the wrong
entry and tries to find correct one.

This can happen if user puts the kretprobe on the function
which can be used in the path of ftrace user-function call.
Such functions should not be probed, so this adds a warning
message that reports which function should be blacklisted.

Tested-by: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/155094059185.6137.15527904013362842072.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Masami Hiramatsu 2019-02-24 01:49:52 +09:00 committed by Greg Kroah-Hartman
parent 5105fc758b
commit 1fab567a27
2 changed files with 27 additions and 0 deletions
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26
arch/x86/kernel/kprobes/core.c
View file

@ -569,6 +569,7 @@ void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
unsigned long *sara = stack_addr(regs);
ri->ret_addr = (kprobe_opcode_t *) *sara;
ri->fp = sara;
/* Replace the return addr with trampoline addr */
*sara = (unsigned long) &kretprobe_trampoline;
@ -759,15 +760,21 @@ __visible __used void *trampoline_handler(struct pt_regs *regs)
unsigned long flags, orig_ret_address = 0;
unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
kprobe_opcode_t *correct_ret_addr = NULL;
void *frame_pointer;
bool skipped = false;
INIT_HLIST_HEAD(&empty_rp);
kretprobe_hash_lock(current, &head, &flags);
/* fixup registers */
#ifdef CONFIG_X86_64
regs->cs = __KERNEL_CS;
/* On x86-64, we use pt_regs->sp for return address holder. */
frame_pointer = &regs->sp;
#else
regs->cs = __KERNEL_CS | get_kernel_rpl();
regs->gs = 0;
/* On x86-32, we use pt_regs->flags for return address holder. */
frame_pointer = &regs->flags;
#endif
regs->ip = trampoline_address;
regs->orig_ax = ~0UL;
@ -789,8 +796,25 @@ __visible __used void *trampoline_handler(struct pt_regs *regs)
if (ri->task != current)
/* another task is sharing our hash bucket */
continue;
/*
* Return probes must be pushed on this hash list correct
* order (same as return order) so that it can be poped
* correctly. However, if we find it is pushed it incorrect
* order, this means we find a function which should not be
* probed, because the wrong order entry is pushed on the
* path of processing other kretprobe itself.
*/
if (ri->fp != frame_pointer) {
if (!skipped)
pr_warn("kretprobe is stacked incorrectly. Trying to fixup.\n");
skipped = true;
continue;
}
orig_ret_address = (unsigned long)ri->ret_addr;
if (skipped)
pr_warn("%ps must be blacklisted because of incorrect kretprobe order\n",
ri->rp->kp.addr);
if (orig_ret_address != trampoline_address)
/*
@ -808,6 +832,8 @@ __visible __used void *trampoline_handler(struct pt_regs *regs)
if (ri->task != current)
/* another task is sharing our hash bucket */
continue;
if (ri->fp != frame_pointer)
continue;
orig_ret_address = (unsigned long)ri->ret_addr;
if (ri->rp && ri->rp->handler) {

1
include/linux/kprobes.h
View file

@ -173,6 +173,7 @@ struct kretprobe_instance {
struct kretprobe *rp;
kprobe_opcode_t *ret_addr;
struct task_struct *task;
void *fp;
char data[0];
};