Commit 568f1967 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Daniel Borkmann
Browse files

bpf: check that BPF programs run with preemption disabled 



Introduce cant_sleep() macro for annotation of functions that
cannot sleep.

Use it in BPF_PROG_RUN to catch execution of BPF programs in
preemptable context.

Suggested-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent a5d9265e

include/linux/filter.h

+1 −1
Original line number Diff line number Diff line
@@ -533,7 +533,7 @@ struct sk_filter { 
	struct bpf_prog	*prog;

};



#define BPF_PROG_RUN(filter, ctx)  (*(filter)->bpf_func)(ctx, (filter)->insnsi)

#define BPF_PROG_RUN(filter, ctx)  ({ cant_sleep(); (*(filter)->bpf_func)(ctx, (filter)->insnsi); })



#define BPF_SKB_CB_LEN QDISC_CB_PRIV_LEN

include/linux/kernel.h

+12 −2
Original line number Diff line number Diff line
@@ -245,8 +245,10 @@ extern int _cond_resched(void); 
#endif



#ifdef CONFIG_DEBUG_ATOMIC_SLEEP

  void ___might_sleep(const char *file, int line, int preempt_offset);

  void __might_sleep(const char *file, int line, int preempt_offset);

extern void ___might_sleep(const char *file, int line, int preempt_offset);

extern void __might_sleep(const char *file, int line, int preempt_offset);

extern void __cant_sleep(const char *file, int line, int preempt_offset);



/**

 * might_sleep - annotation for functions that can sleep

 *
@@ -259,6 +261,13 @@ extern int _cond_resched(void); 
 */

# define might_sleep() \

	do { __might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0)

/**

 * cant_sleep - annotation for functions that cannot sleep

 *

 * this macro will print a stack trace if it is executed with preemption enabled

 */

# define cant_sleep() \

	do { __cant_sleep(__FILE__, __LINE__, 0); } while (0)

# define sched_annotate_sleep()	(current->task_state_change = 0)

#else

  static inline void ___might_sleep(const char *file, int line,
@@ -266,6 +275,7 @@ extern int _cond_resched(void); 
  static inline void __might_sleep(const char *file, int line,

				   int preempt_offset) { }

# define might_sleep() do { might_resched(); } while (0)

# define cant_sleep() do { } while (0)

# define sched_annotate_sleep() do { } while (0)

#endif

kernel/sched/core.c

+28 −0
Original line number Diff line number Diff line
@@ -6162,6 +6162,34 @@ void ___might_sleep(const char *file, int line, int preempt_offset) 
	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);

}

EXPORT_SYMBOL(___might_sleep);



void __cant_sleep(const char *file, int line, int preempt_offset)

{

	static unsigned long prev_jiffy;



	if (irqs_disabled())

		return;



	if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))

		return;



	if (preempt_count() > preempt_offset)

		return;



	if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)

		return;

	prev_jiffy = jiffies;



	printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);

	printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",

			in_atomic(), irqs_disabled(),

			current->pid, current->comm);



	debug_show_held_locks(current);

	dump_stack();

	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);

}

EXPORT_SYMBOL_GPL(__cant_sleep);

#endif



#ifdef CONFIG_MAGIC_SYSRQ

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